economic geology of the alamos mining district, sonora...
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Economic geology of the AlamosMining District, Sonora, Mexico
Item Type text; Thesis-Reproduction (electronic); maps
Authors Vazquez Perez, Adalberto, 1944-
Publisher The University of Arizona.
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Link to Item http://hdl.handle.net/10150/566636
ECONOMIC GEOLOGY OF THE ALAMOS MINING DISTRICT,
SONORA, MEXICO
by
A dalberto Vazquez Perez
A T h esis Subm itted to th e F acu lty o f th e
DEPARTMENT OF MINING AND GEOLOGICAL ENGINEERING
In P a r t ia l F u lf i l lm e n t o f the Requirements For th e Degree o f
MASTER OF SCIENCEWITH A MAJOR IN GEOLOGICAL ENGINEERING
In th e Graduate C o lleg e
THE UNIVERSITY OF ARIZONA
1 9 7 5
STATEMENT BY AUTHOR
T his th e s i s has been su b m itted in p a r t i a l f u l f i l lm e n t o f r e q u i r e ments f o r an advanced degree a t The U n iv e rs ity o f A rizona and i s d e p o s ite d in th e U n iv e rs ity L ib ra ry to be made a v a i la b le to borrow ers under r u le s o f th e L ib ra ry .
B r ie f q u o ta tio n s from th i s th e s i s a re a llo w ab le w ith o u t s p e c ia l p e rm is s io n , p ro v id ed th a t a c c u ra te acknowledgment o f so u rce i s made. R equests f o r p e rm iss io n f o r ex tended q u o ta tio n from o r re p ro d u c tio n o f th i s m an u scrip t in whole o r in p a r t may be g ra n te d by th e head o f th e m ajor departm ent o r th e Dean o f th e G raduate C o lleg e when in h is judgm ent th e p roposed u se o f th e m a te r ia l i s in th e i n t e r e s t s o f s c h o la r s h ip . In a l l o th e r in s ta n c e s , how ever, p e rm iss io n must be o b ta in e d from th e a u th o r .
SIGNED:
APPROVAL BY THESIS DIRECTOR
This th e s i s has been approved on th e d a te shown below :
WILLIAM C. PETERSP ro fe s s o r o f M ining and G eo lo g ica l E n g in ee rin g
/ 77 rDate
Con todo ca r in o a
Pupis
B e t i to
O sca r ito
p or su s s a c r i f i c i o s
ACKNOWLEDGMENTS
I am d eep ly in d eb ted to in d iv id u a ls both on and o f f th e campus
o f The U n iv e r s ity o f A rizona fo r t h e ir su p p ort.
On campus, I w ish to ex p ress my deep a p p r e c ia tio n to Dr. W illiam
C. P e te r s , my m ajor p r o fe s s o r and a d v iso r , to Dr. De V er le P. H arris and
to Mr. Edward J u c e v ic fo r t h e ir gu idance and encouragem ent.
O ff campus, s p e c ia l g r a t itu d e i s due to Ing . G uillerm o P. S a la s ,
General D ir e c to r , and to Ing . Ruben P esquera, E x p lo ra tio n Manager, o f
th e Nonrenewable N atural R esources C ou n cil, as w e ll as th e N a tio n a l
C ouncil o f S c ie n c e and T echnology , o f Mexico fo r t h e ir f in a n c ia l su pp ort
during my s ta y in Tucson.
i v
TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS......................................................................................................v i i
LIST OF TABLES........................................... %
ABSTRACT . ..................................................... .... . . ...................................... x i
1 . INTRODUCTION .............................................................................................................. 1
Purpose and Scope o f Study Methods o f Study . . . .
P re lim inary R econnaissance o f P ro sp ects .............................P h o to g e o lo g ic I n te r p r e ta t io n and F ie ld Check o f
G eo lo g ic U n its and S t r u c t u r e s ............................. .... . . .Underground Mapping and Sam pling o f P ro sp ects . . . .
L ocation and A ccess ...........................................................................................H is to r y and P ast P roduction ........................................................................
2 . REGIONAL GEOLOGY............................ 9
Geomorphology . ..................................................................................................... 9S ie r r a Madre O cc id en ta l P rovince ............................................... 9Sonoran D eser t P rov in ce .......................................................... 13C o a sta l P la in o f S in a lo a P rovince ............................................ 13
S t r a t i g r a p h y ...................................... ................................................ 14P r e c a m b r ia n ................................................................................................ 15P a l e o z o i c ............................................................................ 17M e s o z o ic .............................................................. 20C e n o z o ic .......................................................................................................... 24
S tru c tu re and S tr u c tu r a l H i s t o r y ..................................................... . 26Sonoran D eser t P rov in ce .......................................................... .... . 27S ie r r a Madre O cc id en ta l P rovince ............................................... 28
3 . ALAMOS D IS T R IC T .............................................................................................................. 31
G eneral G eology ..................................................................................................... 31• Geomorphology ............................................................................................ 31
S tr a tig r a p h y ................................................................................................ 33S t r u c t u r e ..................................................................................................... 41
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TABLE OF CONTENTS—C ontinued
Page
Economic G eology ........................................................................ . . . . . 46Ore C o n t r o l .................................................................. 46Ore M ineralogy 49M ineral P a ra g en esis and Zoning .................................. . . . . 50Ore G e n e s i s ................................................................................................ 53D e sc r ip tio n o f Mines ............................................................................. 57
Economic A s p e c t s ............................................................................ 88Grade o f O r e ................................................................................................ 88Ore R e s e r v e s ...................................... 89E x p lo ra tio n P r o g r a m .................................................... 91Economic C o n sid era tio n s ................................................................... 93
4 . STATISTICAL A SP E C T S.................................................... 99
In tr o d u c tio n .......................................................................................................... 99Model and M ethodology Employed . . . . . ............................................... 100M u ltip le R egression A n a ly s is ...................................................................... 104
C onceptual Framework ............................................................................ 104R e su lts o f A n a ly s is ............................................................................. 109
Trend S u rface A n a l y s i s .......................................... 113C onceptual Framework ............................................................................. 113R e su lts o f A n a l y s i s ............................ 116
5 . CONCLUSIONS AND RECOMMENDATIONS .............................................................................. 123
APPENDIX A — ECONOMIC CONSIDERATIONS FOR THE PROSPECTS IN THEALAMOS MINING DISTRICT EXPLORATION PROGRAM, 1973-75 .................... 128
APPENDIX B — STATISTICAL CALCULATIONS FOR THE ALAMOS MININGDISTRICT EXPLORATION PROGRAM, 1973-75 ........................................................ 141
LIST OF REFERENCES................................................................................................................165
v i
LIST OF ILLUSTRATIONS
1. L ocation Map o f th e Alamos M ining D i s t r i c t , Sonora,Mexico ..............................................................................................................
2 . C en tra l P art o f th e Alamos M ining D is t r ic t .............................
3 . Geomorphic P rov in ces in th e S ta te o f Sonora, Mexico . . .
4 . Panoramic View o f th e T e r t ia r y V o lca n ic Rocks W ithin th eBarranca S e c t io n o f th e S ie r r a Madre O c c id en ta l P rov in ce .........................................................................................................
5 . G eo lo g ic Map o f th e S ta te o f Sonora, M exico .............................
6 . G eo lo g ic Map o f th e Alamos D i s t r i c t , Sonora, Mexico . . .
7. Panoramic View o f th e S ie r r a de Alamos .......................................
8. Exposure o f th e Barranca Formation (Upper T r ia ss ic -L o w erJ u r a s s ic ) in th e P ied ras Verdes Area .......................................
9. Ridge o f T e r t ia r y R h y o l it ic Flows D ipping 25° t o th eE a s t ...................................................................................................................
10. L ocation o f P rec io u s-M eta l D i s t r i c t s a lon g th e "MainWelt" S tru c tu re in th e S ie r r a Madre O c c id en ta l P rovin ce .................... ..................................................................................
11. Abundance o f B ase-M etal S u lf id e s P lo t te d A g a in st T h eirH eigh t above Basement ........................................................................
12. P a r a g e n e tic Sequence fo r th e Alamos Mining D i s t r i c t . . .
13. S e c t io n N 30° E Showing Changes in M ineralogy among Minesin th e S ie r r a de Alamos, Alamos D i s t r i c t .............................
14. L ocation and Grouping o f Mines W ithin th e AlamosD i s t r i c t , Sonora, M exico . . ..........................................................
15. Copper M in e r a liz a t io n , B r e c c ia t io n , and A r g i l l i cA lte r a t io n in th e P ied ras Verdes A r e a ........................ . .
F ig u re
v i i
4
5
10
12
In p ock et
In p o ck et
32
36
42
45
48
52
54
In p o ck et
58
Page
v i i i
16. Capping and O x id ation o f th e P ied ra s Verdes P ro sp ect .................... 58
17. S p l i t to th e N 10° W o f th e "Mother Lode" S tru c tu re in th eZapopan T unnel, Q u in tera Mine ................................................................... 61
18. Outcrop o f th e "Mother Lode" S tru c tu re a t th e S u rfa ce 785M eters above Sea L evel .................................................................................. 61
19. G eo lo g ic and Sam pling Map o f th e Prom ontorio M i n e ........................ 63
20. Composite L evel P la n t Map o f th e Q uin tera Mine . .. ............................ 65
2 1 . • G eo lo g ic and Sampling Map o f th e Zapopan L e v e l, 750 M etersabove Sea L e v e l, Q u in tera M i n e ............................................................... 66
22. G eo lo g ic and Sam pling Map o f th e Covacha L e v e l, 730 M etersabove Sea L e v e l, Q u in tera M i n e ................................................................ 67
23. G eo lo g ic and Sam pling Map o f th e L ib ertad L e v e l, 730 M etersabove Sea L e v e l, Q u in tera M i n e .................................................... 68
24. Old Dump o f th e Q uin tera M ine, Alamos D i s t r i c t .................................. 69
25. Gambusinos Who Are Working th e P o r ta l Covacha L e v e l, 730M eters above S ea L ev e l, Q uintera M in e ....................................... 71
26. Minas Nuevas Mine (o r Z am bona)............................ 73
27 . T e r t ia r y R h y o l it ic Flows o f Cerro Cacharamba . . . .... ........................ 75
28 . Exposure a t th e S u rfa ce o f th e San Manuel V e i n .................................. 76
29. P ic tu r e Showing B r e c c ia t io n and O xidation W ithin th e SanManuel V e i n .............................................................................................................. 76
30. G eo lo g ic and Sampling Map o f th e San Manuel M in e ............................. 77
31. G eo log ic C r o ss-S e c tio n and G eo log ic and Sam pling Map o f th ePlom osas M in e .......................................................................................................... 80
32. Sam pling Map o f th e O ta tes M i n e .................................................... 82
33. G eo lo g ic and Sam pling Map o f th e Ana Maria M ine, F ir s t andSecond L ev e ls .......................................................................................................... 84
LIST OF ILLUSTRATIONS— C o n tin u ed
F ig u re Page
ig u r e Page
34. Gambusinos Who Are Working th e Ana Maria M ine, P o r ta l o fSecond L e v e l, 1 ,307 M eters above Sea L evel . . ........................ 85
35. D ir t Roads Which Communicate to th e Ana Maria Mine in th eAlamos D i s t r i c t ............................................................. 85
36. Com posite Plan View and C r o ss-S e c tio n o f th e Japon en MexicoM i n e ........................ ...............................................................................................' . 87
37. Schem atic C r o ss-S e c tio n o f th e Mines W ithin th e "Mother Lode"Vein Showing Areas fo r Ore E x p lo ra tio n ............................................. 92
38. Grid o f C e lls fo r th e Alamos D i s t r i c t ...........................................................102
39. Schem atic R ep resen ta tio n o f th e V a r ia b le s in a Sim pleR egression A n a ly s is ........................................................................................... 106
40. L ocation s o f H ig h e st P r io r i t y P ro sp ectin g Zones E stim ated byM u ltip le R eg ressio n A n a ly s is ................................................................... 114
41. P lo t o f F ir s t D egree E q u ation , Trend S u rface A n a ly s is . . . . 118
42 . P lo t o f Second D egree E qu ation , Trend S u rfa ce A n a ly s is . . . . 119
43 . P lo t o f Third Degree E q u ation , Trend S u rface A n a ly s is . . . . 120
44 . L ocation o f H ig h e st P r io r i t y P ro sp ec tin g Areas A ccording toTrend S u rfa ce A n a l y s i s ........................................................................................121
i x
LIST OF ILLUSTRATIONS— C o n tin u ed
LIST OF TABLES
1. L ith o lo g ic C o r r e la tio n o f Southern A rizona and N orthern Sonora 16
2 . G e o lo g ica l V a r ia b le s Coded fo r th e Alamos M ining D i s t r i c t . . . 103
3. S ig n if ic a n c e o f V a r ia b le s in th e M u ltip le R egression Equationfo r th e Alamos Mining D i s t r i c t ..................................................................... 110
4. S p a t ia l D is tr ib u t io n by C e ll o f Known and P r e d ic te d Mines fo rth e Alamos M ining D i s t r i c t .................................. 112
T a b le Page
x
ABSTRACT
The Alamos M ining D i s t r i c t l i e s in th e E pitherm al P rec io u s M etal
P rov in ce o f n orth w est M exico. I t has been p r a c t ic a l ly in a c t iv e s in c e
1915, n o t from la c k o f m in e r a liz a t io n , b u t from p o l i t i c a l problem s in
th e cou n try .
Based upon g e o lo g ic f a v o r a b i l i t y , the C .R .N .N .R .,* in 1972,
d ecid ed to carry ou t a p re lim in a ry e x p lo r a tio n program to determ ine th e
f e a s i b i l i t y o f i n s t a l l i n g a m i l l and a co n cen tra tio n p la n t in th e
d i s t r i c t .
A fte r th r e e y ea rs o f g e o lo g ic a l reco n n a issa n ce in 108 mine
w ork in gs, th e n in e most fa v o r a b le p r o sp e c ts were s e le c t e d as th e most
im portant fo r fu r th e r e x p lo r a t io n .
An e x p lo r a tio n and p r e lim in a r y developm ent program i s recommended;
i t i s based upon in d ic a t io n s th a t a t l e a s t 500 ,000 m e tr ic to n s , w ith a
grade o f 400 gram s/ton s i l v e r , 0 .6 7 gram s/ton g o ld , 2.88% le a d and 3.38%
z in c may b e found. In a d d it io n , fa v o ra b le g e o lo g ic a l c o n d it io n s in d ic a te
p o t e n t ia l ore r e se r v e s o f 1 m i l l io n m etr ic to n s w ith a s im ila r grade.
P r o f i t a b i l i t y a n a ly se s show th a t th e d i s t r i c t i s an a t t r a c t iv e
p r o je c t f o r in v estm en t. The amount o f th e c a p it a l in vestm en t fo r
d ev e lo p in g th e n in e p r o sp e c ts i s e s tim a ted a t 2 m il l io n d o l la r s , in c lu d in g
e x p lo r a tio n and developm ent.
*C onsejo de R ecursos N a tu ra les no R enovables, a governm ental in s t i t u t i o n .
x i
x i i
F in a l ly , g e o s t a t i s t i c a l a n a ly s is , m u lt ip le r e g r e s s io n and tren d
su r fa c e tech n iq u es in d ic a te th a t th e Alamos M ining D i s t r i c t shows
fa v o r a b le a rea s o f e x p lo r a tio n p o t e n t ia l in a d d itio n to th e known ore
b o d ie s .
CHAPTER 1
INTRODUCTION
Purpose and Scope o f Study
T h is stu d y i s th e p re lim in a ry r e s u l t o f a su rvey o f th e g eo lo g y
and ore d e p o s it s o f th e Alamos Mining D i s t r i c t , Sonora, M exico. The
o r ig in a l purpose was to determ ine th e f e a s i b i l i t y o f i n s t a l l i n g a concen
t r a t io n p la n t .
S in c e th e main g o a l o f th e su rvey was a q u ick , b u t e f f e c t i v e ,
e v a lu a t io n o f m ines and p r o s p e c ts , th e in v e s t ig a t io n was p lanned as a
rec o n n a issa n ce su rv ey . T h is l e f t no tim e fo r b a s ic and d e t a i le d g e o lo g ic
s tu d ie s in v o lv in g s e c t io n m easuring and g eo ch ro n o lo g ic d e term in a tio n s .
W isser (1966) p rov id ed an e x c e l le n t stu d y o f econom ic g eo lo g y in n o r th
w estern Mexico and King (1939) c a r r ie d ou t a r e g io n a l g e o lo g ic stu d y in
sou thern Sonora; th e se are used as a b a s is fo r c l a s s i f y i n g th e ore
d e p o s its and e s t a b l is h in g th e s t r a t ig r a p h ic column in th e Alamos Mining
D is t r i c t .
I t i s hoped th a t t h i s p re lim in a ry stu d y o f th e Alamos M ining
D is t r i c t m ight be o f some h e lp to th e f i e l d g e o lo g is t s o f th e C .R.N.N.R.
in t h e ir stu d y o f t h is d i s t r i c t and s im ila r d i s t r i c t s . A lso , th e in f o r
m ation p resen ted h ere m ight c a l l th e a t te n t io n o f th e G eneral D ir e c to r 's
O ff ic e o f th e C .R .N .N .R. to th e need fo r in v e s t ig a t in g th e a rea in more
d e t a i l .
1
2
Methods o f Study
The stu d y was c a r r ie d o u t in th ree p h ases: 1) p re lim in a ry
reco n n a issa n ce o f p r o s p e c ts , 2) p h o to g e o lo g ic in t e r p r e ta t io n and f i e l d
check o f g e o lo g ic a l u n it s and s t r u c t u r e s , and 3) underground mapping and
sam pling o f p r o s p e c ts .
P re lim in ary R econnaissance o f P ro sp ects
T his phase o f th e program was conducted in p erson from J u ly 1972
t o March 1973. During t h i s p e r io d , 108 p r o s p e c ts , ran g in g from sm all
tren ch es to m ines w ith s e v e r a l l e v e l s , were v i s i t e d . I t was im p o ss ib le
to reach th e lo w est l e v e l s o f th e m a jo r ity o f th e mines b ecau se o f t h e ir
c o n d it io n . T h erefo re , r e p r e s e n ta t iv e ch ip and channel sam ples from th e
v e in s w ere taken o n ly a t 60% o f th e p r o s p e c ts . At th e rem aining 40% o f
th e p r o s p e c ts , sam ples from th e dumps were taken b ecau se no v e in s were
exposed . A d m itted ly , t h i s ty p e o f sam pling i s n o t r e p r e s e n ta t iv e , b u t
i t g iv e s an id e a o f th e o re th a t was mined.
F ive hundred sam ples w ere c o l le c t e d during t h i s p h a se . They were
an a lyzed to determ ine t h e ir co n ten t o f s i l v e r (A g), le a d (P b ), z in c (Z n ),
copper (C u), and g o ld (A u). T h is was done by u t i l i z i n g th e atom ic
a b so rp tio n u n it a t th e N o g a les , Sonora, o f f i c e o f th e C .R .N .N .R.
The lo c a t io n o f m ines was p lo t t e d on a to p ograp h ic map a t a
s c a le o f 1 :2 5 0 ,0 0 0 b ecau se no la r g e r s c a le maps were a v a i la b le .
P h o to g e o lo g ic I n te r p r e ta t io n and F ie ld Check o f G eo lo g ic U n its and S tr u c tu r e s
The seco n d p h a se o f th e p rog ram was co n d u c ted by th e a u th o r from
March to May, 1973, and from May to J u l y , 1974. T h is was done w ith b la c k
3
and w h ite a e r ia l photographs a t an approxim ate s c a le o f 1 :5 5 ,0 0 0 . The
su r fa c e mapping was p lo t t e d accord in g to th e accuracy p erm itte d by th e
photo s c a le . A g e o lo g ic map was co n stru c ted on th e b a s is o f an uncon
t r o l l e d photom osaic a t th e same s c a le as th e a e r ia l ph otograp hs. The
photom osaic covers a su r fa c e o f 1 ,200 square k ilo m e te r s . A lthough t h i s
i s o n ly about 50% o f th e area in which th e p r o sp e c ts and m ines are
lo c a te d , th e most im portant p r o sp e c ts l i e in th e area mapped.
Underground Mapping and Sam pling o f P ro sp ects
T his phase o f th e program was done by Raul Munoz, J o se P erez and
A lfred o C ervantes o f th e C .R .N .N .R. from O ctober o f 1973 to d a te , and by
th e au thor during m id -Ju ly o f 1974. During t h i s p e r io d , two m in es,
Q uintera and Prom ontorio, were p a r t i a l l y dew atered and c lea n ed fo r
d e t a i le d sam pling and mapping. A lso , some sm all p r o sp e c ts w ere c lea n ed
and mapped. Mapping c o n tr o l was by brunton compass and ta p e , and th e
s c a le o f mapping was 1 :1 ,0 0 0 . E leven m ines and p r o sp e c ts have been
mapped and sam pled to th e p r e se n t tim e . They were s e le c t e d in order o f
p r io r i t y , based upon g e o lo g ic f a v o r a b i l i t y . In t h i s p ap er , o n ly n in e o f
th e most im portant p r o sp e c ts are d e sc r ib e d .
L ocation and A ccess
The Alamos M ining D i s t r i c t i s lo c a te d in th e sou th ern p a r t o f
th e s t a t e o f Sonora, M exico, approxim ately 40 k ilo m e te r s e a s t o f N avojoa
(F igu re 1 ) . Roughly, th e d i s t r i c t covers about 2 ,0 0 0 square k ilo m e te r s ;
th e most m in era lize d p a r t , which i s lo c a te d in th e c e n te r o f th e d i s t r i c t ,
covers about 100 square k ilo m e te r s (F igure 2 ) .
2S ~ \C o b o rco e s° oMogdoleno •,
S O N O R A (| ©Hermositlo \
ALAMOS
DISTRICT
50 0
k ilo m e te rs
F ig u re 1. L ocation Map o f th e Alamos Mining D i s t r i c t , S onora, Mexico.
5
Cocim
Europ
18 may
Cobn
f t Mine or prospect
A East vain,'mother lode
B' Wast va i n Infer rad vein
F igu re 2. C e n tra l P a r t o f th e Alamos Mining D i s t r i c t .
6
The major town i s Alamos, p o p u la tio n 5 ,0 0 0 . The a c c e s s . t o
Alamos i s by a 5 2 -k ilo m e te r branch road from th e main P a c i f i c c o a s t road
a t N avojoa. A ccess to o th er towns and sm all v i l l a g e s in th e d i s t r i c t i s
by d ir t ro a d s , which are d i f f i c u l t to tr a v e l upon during th e ra in y
sea so n (J u ly to Septem ber).
H isto r y and P a st P roduction
As w ith many Mexican m ining d i s t r i c t s , th e m ining h is t o r y o f th e
Alamos M ining D i s t r i c t i s n o t w e ll known. T h erefo re , th e fo llo w in g
d e s c r ip t io n can be co n sid ered as a h i s t o r i c a l sk etch based upon th e
sp a rse a v a ila b le in fo rm a tio n .
Among th e g e o lo g is t s who d escr ib ed th e d i s t r i c t ' s h is t o r y are:
R ickard (1 9 0 4 ) , Pearce (1 9 1 0 ) , P earce (1 9 1 1 a ,b ) . Bloomer (1 9 0 9 ) ,
B rinegar (1 9 1 0 ) , and Sheldom (1 9 1 0 ). A ll v i s i t e d th e d i s t r i c t when th e
mines were o p e r a tin g . Q uiroga (1 9 5 3 ) , Labounsky (1957) , and W isser
(1966) v i s i t e d th e d i s t r i c t when no mines were o p e r a tin g .
Sheldom (1910) s ta t e d th a t v e in s co n ta in in g s i l v e r and go ld
m in era ls were d isc o v e r e d by th e Spanish J e s u i t s in th e e ig h te e n th
cen tu ry . They worked th e m in es, p r in c ip a l ly th e Prom ontorio , and
e x tr a c te d m eta l from h igh grade, hand p ick ed ore in crude sm e lte r s
w ith o u t p r io r m i l l in g . The Spaniards worked th e m ines u n t i l about 1800
when p o l i t i c a l problem s p rev en ted them from c o n tin u in g . Sheldom r e la t e s
th a t , in th e y ea r 1857, a Frenchman owned th e Q uin tera m ine. He went to
to P a r is and m ortgaged th e mine to th e E gyptian P a r is Bank f o r
$ 2 5 0 ,0 0 0 .0 0 . A fte r t h a t , w ith Tom Clark as th e m in e 's manager, th e mine
7
p a id from $ 5 0 ,0 0 0 .0 0 to $ 1 0 0 ,0 0 0 .0 0 in annual d iv id en d s fo r many y e a r s ,
even though m il l in g was e x p e n s iv e . Sheldom (1910 , p . 920) fu r th e r
s t a t e s : "Under th e management o f J . H. Hendra . . . th e Santo Domingo
Mine has been d eveloped and a m il l has been e r e c te d . T h is ran l a s t
y ea r u n t i l th e p o l i t i c a l d is tu rb a n c es sh u t th in g s down."
A ccording to B rinegar (1 9 1 0 ), th e s i l v e r p rod u ction became so
g r e a t in th e 1 8 9 0 's th a t th e Mexican government e s ta b lis h e d a m int in
Alamos fo r c o in in g th e m eta ls produced a t t h i s p o in t . He a ls o m entions
t h a t , in 1808, Von Humbolt n o ted in h is record s " th a t he p a ssed a t r a in
o f one thousand m ules loaded w ith b ars o f s i l v e r from t h i s d i s t r i c t on
t h e ir way t o th e C ity o f Mexico" (p . 5 5 3 ).
Other im portant and in t e r e s t in g in fo rm a tio n i s g iv en by Rickard
(1904) and P earce (1 9 1 0 ) , who em phasized n o t o n ly th e s i l v e r p rod u ction
b u t a ls o th e p o s s ib le copper p ro d u ctio n in th e d i s t r i c t , p r in c ip a l ly
from th e P ied ra s Verdes a rea .
Labounsky (1957) i n s i s t s th a t th e u n c e r ta in ty cre a ted by p o l i t i c a l
problem s, nam ely the Mexican R ev o lu tio n o f 1910-1920, w ere s e r io u s
d e te r r e n ts to o b ta in in g fo r e ig n in v estm en ts to d evelop Mexican m ines.
However, he m en tion s, in r e s p e c t to th e Alamos M ining D i s t r i c t (Labounsky,
1957, p . 4 ) : "The e n t ir e m ining camp was sh u t down in 1911 when th e
s i l v e r p r ic e w ent down to 48 cen t p er ounce."
A ccording to a paper by Vazquez (1 9 7 3 ), an American company
m ille d o re a t a r a te o f 300 ton s p er day from th e dumps during th e p e r io d
1948 to 1957. The Mexican governm ent, in 1959-1960, i n s t a l l e d a p i l o t
p la n t fo r m i l l in g ore from dumps. A pparently , th e r e were a d m in is tr a t iv e
and te c h n ic a l prob lem s, and th e p i l o t p la n t was removed in 1962.
At th e p r e se n t tim e , o n ly a few mines are a c t iv e . These in c lu d e
th e O ta te s , P lom osas, Q u in tera , San Manuel, Q u ir ie g o , La R eina , and La
V io le ta . B ecause th ere i s p r a c t ic a l ly no m ining equipment i n s t a l l e d in
th e m ines, p rod u ction i s s m a ll, ranging from 1 to 5 to n s p er day p er
m ine; In th e Q uin tera and Q u ir iego m ines, th e m ining o p e r a tio n s are
r e s t r i c t e d to th e dumps b ecau se o f poor underground c o n d it io n s and lack
o f m ining equipm ent. The mined ore i s s e n t to Chihuahua C ity , 600
k ilo m e te r s away, o r to La Reforma, S in a lo a , 300 k ilo m e te r s away, fo r
c o n c e n tr a tio n and p r o c e s s in g b ecau se th e se are th e n e a r e s t p la n ts fo r
p r o c e ss in g s i l v e r - l e a d m in e r a ls .
In r e s p e c t to p a s t p ro d u ctio n , Sheldom (1910) s t a t e s th a t th e
"Mother Lode" Q uintera-P rom ontorio has been worked p r a c t ic a l ly con
t in u o u s ly fo r 200 y e a r s . He p o in t s out (Sheldom, 1910, p . 5 2 4 ): "These
dumps are immense and co n ta in e a s i l y o n e -h a lf m il l io n to n s . They are
s u f f i c i e n t l y v a lu a b le to w arrant r e -tr e a tm e n t. I t i s c la im ed th a t th e
mines have produced 100 m il l io n d o l la r s b u t t h is i s p rob ab ly ex a g g era ted ."
W isser (1966) e s t im a te s a d i s t r i c t ' s p a s t p ro d u ctio n a t 150
m il l io n d o l la r s . T h ere fo re , i t seems l i k e l y th a t th e d i s t r i c t ' s produc
t io n was somewhere betw een $ 1 0 0 ,0 0 0 .0 0 and $ 1 5 0 ,0 0 0 .0 0
8
CHAPTER 2
REGIONAL GEOLOGY
Geomorphology
A lvarez (1966) made an e x c e l le n t com p ila tio n and r e - in t e r p r e t a t io n
o f M exico’ s geom orphology, based la r g e ly on King (1939) and De C sem a
(1 9 6 0 ). He concluded th a t th e s t a t e o f Sonora com prises th r e e geom orphic
p r o v in c e s: S ie r r a Madre O c c id e n ta l, Sonoran D e se r t , and C o a sta l P la in
o f S in a lo a (F igu re 3 ) .
S ie r r a Madre O cc id en ta l P rov in ce
The S ie r r a Madre O c c id en ta l i s a m ountainous b e l t 1 ,200 k ilo m e te r s
lo n g , w ith an average w id th o f 250 k ilo m e te r s . The s ie r r a tren d s n o rth
ward to n o rth w est 1 0 ° , and ex ten d s from la t i t u d e s 20° to 31°N, where i t
reach es th e U nited S ta te s b ord er. The S ie r r a Madre O cc id en ta l P rov in ce
i s d iv id e d in to th ree su b p rov in ces o r s e c t io n s : P la te a u , B arranca, and
B asin and Range (A lv a rez , 1966 ).
P la tea u S e c t io n . T his s e c t io n l i e s in th e m ost e a s te r n p a r t o f
th e s t a t e o f Sonora and p a r t ia l l y in th e s t a t e o f Chihuahua. I t shows a
g e n t ly r o l l in g su r fa c e carved from v o lc a n ic ro ck s . E le v a t io n s range from
2 ,0 0 0 to 2 ,9 0 0 m eters . There are ir r e g u la r m ountains sep a ra ted by broad
and f l a t v a l l e y s . The v a l l e y s are drained by t r ib u t a r ie s o f th e Y aqui,
Mayo, and F uerte r i v e r s , which flo w through th e deep gorges or barrancas
o r th e Barranca s e c t io n toward th e G ulf o f C a lifo r n ia . O utcropping
9
10
rCSon Luis Rio Colorado
A
( / X \NocozorideGorcio *. *
l ! \ : ( !
/ / T 8!.......... a u - S S ia - v -< Coborco ' / / : o ; !
/ ' X a & l i o r ~ Cononeo
\ X - ' y - s : r r o,- °
r X ? 4 ' - . ,
y j <y ' *—-(fMozocohui )
r - u ^ r / / . / > */ ( \ ? ^ / O pH ERM O Sl'ab'
Tecoript
E X PL AN AT ION
f Sonoran Desert Province
E S i e r r a Madre Occidental Province
A ) Basin and Range Section
B ) B a r r a n c a Sec t ion
C ) Plateau S e c t i o n
EL Coastal Plain of Sinaloa ProvinceALAMOS
DISTRICT
5 0 70 i50
ki lomete rs250
F ig u re 3. Geomorphic P ro v in ces in th e S ta te o f Sonora, Mexico.
rocks c o n s is t p r in c ip a l ly o f T e r t ia r y r h y o l i t i c f lo w s . In a few p la c e s
th ey are known to o v e r l ie fo ld e d M esozoic ro ck s .
Barranca S e c t io n . T h is s e c t io n i s a lo n g itu d ia n l b e l t o f 40 to
90 k ilo m e te r s w ide and 600 k ilo m e te r s lo n g . The c h a r a c t e r is t ic geomor-
p h ic fe a tu r e s o f t h i s s e c t io n are y o u th fu l . R ivers have carved deep
gorges or barrancas p a r a l l e l to th e r e g io n a l , N10°W, tren d o f th e S ie r r a
Madre. Some o f th e gorges reach 2 ,0 0 0 m eters in depth . Exposed rocks
w ith in t h i s su bp rovince c o n s is t p r in c ip a l ly o f T e r t ia r y r h y o l i t e s and
a s s o c ia te d v o lc a n ic r o c k s , and sc a r c e sed im entary and in t r u s iv e rocks
which have been r a is e d by f a u l t s to th e zone o f e r o s io n (F igu re 4 ) .
B asin and Range S e c t io n . T his subprovince i s a b e l t 80 to 110
k ilo m e te r s w ide in e a s t - c e n t r a l Sonora, bu t co n s id e r a b ly narrow er in
n o r th e a s te r n Sonora. I t i s 500 k ilo m e te r s long and ex ten d s toward th e
n orth in th e U nited S ta te s where i t forms th e Great B asin S e c t io n o f th e
B asin and Range P ro v in ce . The main p h y sio g ra p h ic fe a tu r e i s a s e r ie s o f
p a r a l l e l m ountain ranges and in term ontane v a l le y s th a t form h o r s ts and
grabens. Some o f th e ran ges from n orth to sou th are th e San A n ton io , •
Cananea, P u r ica , Copper Queen, N a co za r i, A eon ch i, Sahuaripa, Moctezuma,
Soyopa, and Alamos. They range from 1 ,500 to 2 ,0 0 0 m eters in h e ig h t .
The v a l l e y s are d ra in ed by th e B ab isp e , Moctezuma, Sonora, Y aqui, and
Mayo r i v e r s , w hich flo w toward th e G ulf o f C a lifo r n ia . Rocks ou tcrop p in g
in t h i s s e c t io n c o n s is t o f sed im en ta ry , v o lc a n ic and in t r u s iv e rocks
ranging in age from P a le o z o ic to R ecen t.
11
F igu re 4. Panoramic View o f th e T e r t i a r y V olcan ic Rocks W ithin th e B arranca S e c tio n o f th e S ie r r a Madre O cc id en ta l P ro v in ce . — A y o u th fu l topography i s e v id e n t .
N)
13
Sonoran D esert P rovince
T his p h y sio g ra p h ic p ro v in ce cov ers about 50% o f th e s t a t e o f
Sonora and ex ten d s toward th e n orth in th e U nited S ta te s where i t forms
th e Mohave and G ila D esert (Thom bury, 1965). The p ro v in ce c o n ta in s
e x te n s iv e p la in s th a t descend from 700 m eters to s e a l e v e l a t th e G ulf
o f C a lifo r n ia . The landscape i s composed o f i s o la t e d r id g e s , m o stly
w ith o u t a d e f in i t e o r ie n ta t io n , w hich show a mature p h ysiograp hy.
A llu v ia l fa n s , pedim ents and c u e s ta s are common fe a tu r e s a t th e b ase o f
th e m ountains. Some o f th e ranges from n orth to sou th are P in a c a te ,
Cubabi, G u ija s , C uevas, C olorada, B a c a te te , B u en a v ista , and B aroyeca,
which range from 600 to 1 ,0 0 0 m eters in h e ig h t . R ivers in th e Sonoran
D esert P rov in ce are th e S o n o ita , A lta r , Bacabache, and Sonora, which
d rain toward th e G ulf o f C a lifo r n ia . Exposed rocks c o n s is t m ain ly o f
PreCambrian and P a le o z o ic r o c k s .
C oasta l P la in o f S in a lo a P rov in ce
T h is p ro v in ce i s lo c a te d in th e sou thern p a r t o f th e s t a t e o f
Sonora and ex ten d s to th e sou th in th e s t a t e o f S in a lo a . The C o a sta l
P la in i s an e lo n g a ted b e l t from 25 to 100 k ilo m e te r s w ide and 300
k ilo m e te r s lo n g . The p ro v in ce i s composed o f a l l u v i a l p la in s which have
been formed by th e c o a le s c in g o f th e d e lta s o f th e Yaqui and Mayo r iv e r s
in th e n orth and th e F u erte , S in a lo a and R osario r iv e r s fa r th e r so u th .
King (1939) su g g e s ts th a t th e s h o r e lin e i s em ergent w ith c h a r a c t e r i s t ic
o ffs h o r e bars sep a ra ted from th e m ainland by t i d a l f l a t s and la g o o n s .
14
. S tra tig ra p h y
In 1974, th e g eo lo g y o f th e s t a t e o f Sonora was known o n ly in a
g en era l manner b ecau se th e r e had been d e ta i le d g e o lo g ic a l su rveys in o n ly
a few l o c a l i t i e s . The s t a t e covers 182,000 square k ilo m e te r s o f which
o n ly 10 ,000 square k ilo m e te r s have been mapped in d e t a i l (S a la s , 1971 ).
I t i s e s t im a ted th a t 9 0 ,000 square k ilo m e te r s are covered in s e m i-d e ta i l
and th a t th e rem aining 8 0 ,000 square k ilo m e te r s have been mapped in
re c o n n a issa n c e . M oreover, i t i s co n sid ered th a t 80% o f such d e t a i le d
and s e m i-d e ta ile d mapping has been done in the. c e n tr a l-n o r th e r n p a r t o f
th e s t a t e , from 29° la t i t u d e n o r th . U ndoubtedly, t h i s i s b ecau se
d e ta i le d s tu d ie s have been made in sou thern A rizon a , in th e U n ited S t a t e s ,
and much o f th a t g e o lo g ic knowledge i s a p p lic a b le to n orth ern Sonora.
Among th e g e o lo g is t s who have s tu d ie d and p u b lish e d on th e
r e g io n a l g eo lo g y o f n orth ern Sonora are Durable (1 9 0 0 ) , Angermann (1 9 0 4 ) ,
F lo res (1 9 2 9 ) , Im lay (1 9 3 9 ) , Cooper and A rellan o (1 9 4 6 ) , A re lla n o (1 9 5 6 ) ,
Mulchay and V elasco (1 9 5 4 ) , F r ie s (1 9 6 2 ) , De C sem a (1 9 6 0 ) , De C sem a
and A le n c e s te r (1 9 6 1 ), S a la s (1 9 7 0 ) , and th e C .R .N .N .R .-U n ited N ation s
(1 9 6 9 ). I s o to p ic age d e term in a tio n s have been made by Damon, L iv in g s to n ,
and G i l e t t i (1 9 6 2 ) , Damon and Mauger (1 9 6 6 ) , Damon and Bikerman (1 9 6 4 ) ,
Damon e t a l . (1 9 6 5 ) , Damon (1 9 6 8 ) , and L iv in g sto n (1 9 7 3 ) .
On th e o th e r hand, th e r e g io n a l g eo logy o f sou th ern Sonora, from
29° la t i t u d e so u th , has been s tu d ie d o n ly by F lo res (1929) and King
(1 9 3 9 ).
B ased upon th e work o f th e a u th o rs p r e v io u s ly c i t e d , and on th e
s t a t e g e o lo g ic map, a g e n e ra l d e s c r ip t i o n o f th e g eo lo g y o f th e s t a t e o f
15
Sonora i s shown in F igure 5 ( in p o ck et; Comite de l a C arta G eo lo g ica de
M exico, 1 968 ). T able 1 shows th e com posite s t r a t ig r a p h ic column.
Precambrian
Precam brian rock s t h a t ' outcrop in th e s t a t e o f Sonora are both
O lder and Younger Precam brian. T his d iv is io n i s based on W ilso n 's
term in o logy (F r ie s , 1962) and corresponds t o th e M azatzal R ev o lu tio n .
T his metamorphic ev en t has been e s tim a te d a t 1 ,700 my o ld . However,
Damon (1968) c o n s id e r s , by ap p ly in g new age d e te r m in a tio n s , th a t th e
M azatzal R ev o lu tio n occu rred betw een 1 ,370 and 1 ,4 5 0 my ago, and th a t a
metamorphic ev en t in A rizona and Sonora occurred betw een 1 ,630 and
1 ,760 my ago. T h is l a s t ev en t i s c a l l e d , by Damon, th e A rizonan R evolu
t io n . In t h i s p ap er , th e A rizonan R evo lu tion i s taken as a b a s is fo r
d iv id in g th e Precam brian.
The O lder Precambrian rock s outcrop in th e v i c i n i t y o f A lta r ,
Bamori, and Magdalena in n orth w estern Sonora, and S ie r r a San A ntonio and
C abullona in n o r th e a ste r n Sonora. At A lta r , th ey are re p r e se n te d by a
sed im entary sequence o f s h a le , lim e s to n e , d o lo m ite , and q u a r t z i t e , w ith
a th ic k n e s s o f 1 ,7 0 0 m eters (Cooper and A r e lla n o , 1 946 ). In th e v i c i n i t y
o f Bamori, 20 k ilo m e te r s sou th o f Caborca, th ey are composed o f s c h i s t s ,
q u a r t z i t e s , and m eta v o lc a n ic s (Damon e t a l . , 1962; Damon, 1 968 ). At
Magdalena, th e rock s c o n s is t o f low -grade c a l c - s c h i s t m arble and g r a n ite
g n e is s m etasedim ents (S a la s , 1970 ). In th e C abullona a r e a , th e O lder
Precambrian i s r e p r e se n te d by a m icaceous s c h i s t (T a lia fe r r o , 1 9 3 3 ),
which i s c o r r e la te d w ith P in a l S c h is t o f sou th ern A rizona. At S ie r r a de
San A n ton io , a s im ila r s c h i s t i s a ss ig n e d t o t h i s age (R am irez, 1 9 6 5 ).
T able 1. L ith o lo g ic C o r r e la t io n o f Southern A rizona and N orthern Sonora. — A fte r Luque (1 9 7 4 ).
Era P eriod Epoch . Southern A rizona N orthern Sonora
C enozoic Q uaternary R ecent A lluvium , g r a v e l , s i l t A lluvium , g r a v e lP le is to c e n e B a s a lt , e l a s t i c s B a s a lt , e l a s t i c s
T e r t ia r y P lio c e n e G ila conglom erate B a u ca r it Form ationMiocene ? U nconform ityO lig o cen e - R h y o lite s , a n d e s it e s , U n d if fe r e n t ia te d
Eocene t u f f s , g r a n it ic v o lc a n ic r o c k s ,in tr u s iv e s a n d e s it e s , rhyo
l i t e s , g r a n i t i c in t r u s iv e s
P a leocen e Unconform ity U nconform ityM esozoic C retaceous V o lca n ic and in t r u s iv e P otrero and Palmar
ro ck s; B isb ee Group U nconform ity
Form ations
J u r a s s ic U n d if fe r e n t ia te d v o lc a n ic R epreso, L is tarocks B lanca Formation
U nconform ityT r ia s s ic U nconform ity Barranca Formation
unconform ityP a le o z o ic Permian Naco Group (?) P u e r te c ito s Formation
C arboniferous E scabrosa Form ation R epreso FormationDevonian M artin Formation M urcielago FormationS i lu r ia n A brigo Form ation L im eston e, sh a leO rdovician B o lsa q u a r tz it e Esperanza FormationCambrian U nconform ity . U nconform ity
PreCambrian S u p er io r Apache Group, l im e s to n e s . C o c o t i l lo Group,s h a le s s h a le s , lim esto n es
U nconform ity U nconform ityM iddle . P in a l s c h i s t and P in a l s c h i s t and
g r a n ite .............. g r a n ite
17
The Younger PreCambrian rock s outcrop in Caborca, A ibo, S o n o ita ,
and Madgalena in n orth w estern Sonora. At Caborca, th ey c o n s is t o f an
in terb ed d ed sequence o f q u a r t z i t e , s h a le , l im e s to n e , and d o lo m ite , w ith
a th ic k n e s s o f 2 ,0 0 0 m eters (Cooper and A r e lla n o , 1946). These P re-
cambrian sed im entary rocks have been compared to th e Apache Group and
Grand Canyon S e r ie s o f A rizona and th e Pahrump S e r ie s o f C a lifo r n ia by
A rella n o (1956) and by F r ie s (1 9 6 2 ) . In th e v i c i n i t y o f Aibo (Cerro d e l
Arpa) th ey are r ep re se n ted by an a lt e r e d red grap h ic g r a n ite on which
th e la t e r sed im en tary rock s r e s t unconform ably (Damon, 1 9 6 8 ). In th e
S o n o ita D i s t r i c t , th e P in a c a te g n e is s i s co n sid ered to b e lo n g to t h i s
age (Damon, 1 9 6 8 ). Near Magdalena, th e Younger Precambrian i s r e p r e
sen ted by low -grade p h y l l i t e , q u a r t z i t e , m etaconglom erate, and m arble,
w ith a th ic k n e s s o f more than 2 ,0 0 0 m eters (S a la s , 1 970 ). F r ie s (1962)
e s t im a te s th a t th e th ic k n e s s o f th e Younger Precambrian rock s d ecre a se s
toward th e e a s t , where th e Precambrian i s o n ly a few m eters in th ic k n e s s
o r has been removed co m p le te ly by e r o s io n .
P a le o z o ic
Rocks o f t h i s age have been rec o g n ized throughout th e s t a t e o f
Sonora, even though th e com plete s t r a t ig r a p h ic column o f t h i s p e r io d i s
d o u b tfu l. The m ost d e t a i le d s tu d ie s o f P a le o z o ic rocks have been c a r r ie d
out by Cooper and A re lla n o (1946) and by A re lla n o (1956) in th e A lta r
and Caborca a r e a s , where exposures o f P a le o z o ic rock s are found.
18
Cambrian. S tr a ta o f Cambrian age crop out e x t e n s iv e ly w ith in th e
A lta r and Caborca d i s t r i c t s (Cooper and A r e lla n o , 1946). In th e s e d i s
t r i c t s , th e rocks c o n s is t o f a s t r a t i f i e d sequence o f lim e s to n e s , s h a le s ,
and q u a r t z i t e s , w ith a th ic k n e s s o f more than 1 ,200 m eters , r e s t in g uncon-
form ably on Precambrian ro ck s . Cooper e t a l . (1952) d iv id e th e Cambrian
sed im entary rocks a t Cerro La Provedora in to s i x form ation s ran gin g from
Lower to M iddle Precam brian. A ll th e form ation s were sep a ra ted accord in g
to c h a r a c t e r is t ic f o s s i l s . In th e Cananea D i s t r i c t , th e Cambrian i s
rep re se n ted by lim esto n e and q u a r t z i t e , w ith a th ic k n e s s o f 100 m eters
(Mulchay and V e la sc o , 1954).
O rd ov ic ian . King (1939) i d e n t i f i e s rock a t La C a s ita and a t
S ie r r a de C obachi, 70 k ilo m e te r s so u th e a s t o f H e rm o sillo , as b e in g Ordo
v ic ia n . At both l o c a l i t i e s , a m assive lim esto n e about 50 m eters th ic k
co n ta in s Richmond C oral Fauna. He d e sc r ib e s (K ing, 1939, p . 1641): " I t
i s a s s o c ia te d w ith a b la ck lim esto n e w ith chery la y e r s and c o n c r e t io n s ,
q u a r tz it e and s i l i c e o u s s h a le . F o s s i l s are n o t found in th e se beds b u t
th ey may be o f Lower O rdovician a g e ." F r ie s (1 9 6 2 ) , how ever, th in k s th a t
t h i s s t r a t ig r a p h ic u n it s corresponds to Upper Precam brian.
S i lu r ia n . No rocks o r f o s s i l s o f t h is age have been rep o rted in
Sonora, even though F r ie s (1962) assumes th a t , n ear La C a s ita and
C obachi, th e r e are p rob ab ly sed im entary rocks o f t h i s p e r io d .
D evonian. Sedim entary rocks o f Devonian age are id e n t i f i e d as
Lower and Upper D evonian. Lower Devonian rocks are exposed in th e A lta r
and Cananea D i s t r i c t s (Cooper and A r e lla n o , 1946; Maldonado, 1 9 5 4 ). They
19
are composed o f a sed im en tary sequence o f lim esto n e and d o lom ite w ith a
th ic k n e ss o f 285 m eters .
Upper Devonian rocks are exposed in th e C abullona area (A lv a rez ,
1 9 6 6 ), where th ey c o n s is t o f a com pact, g rey -b la c k lim esto n e a s s o c ia te d
w ith i n t e r s t r a t i f i e d beds o f c le a r lim e sto n e . At th e base o f t h i s
form a tio n , th e r e i s a p in k , carbonaceous sh a le 100 m eters in th ic k n e s s .
No f o s s i l s have been found in t h i s l a s t u n it .
M is s is s ip p ia n . Rocks th a t have been c l a s s i f i e d as M iss is s ip p ia n
in age are exposed in th e A lta r , C abullona, and E l T ig re a r e a s . At
A lta r , th ey c o n s is t o f a c r in o id a l , grey lim esto n e w ith abundant co n cre
t io n s o f q u a rtz . T h is form ation i s named R isa n i by T o rres , I s a b a l , and
Gomez (A lv a rez , 1 9 6 6 ), and th ey c o r r e la te t h i s u n it w ith th e E scabrosa
form ation in sou th ern A rizon a . In th e C abullona a rea , M is s is s ip p ia n
rocks s im ila r to th e R isa n i form ation were s tu d ie d by T a lia fe r r o (1 9 3 3 ).
At El T ig r e , in th e Canon Santa R osa, Imlay (1939) r e c o g n iz e s a sequence
o f c r in o id a l lim e sto n e s and s h a le s w ith a th ic k n e s s o f 380 m eters as
b e lo n g in g to th e Lower M is s is s ip p ia n .
P en n sy lv a n ia n . S tr a ta o f P ennsylvan ian age are exposed w ith in
th e Cananea, C abullona, and E l T ig re d i s t r i c t s . In th e v i c i n i t y o f
Cananea, a f i n e , s t r a t i f i e d lim esto n e ou tcrop s w ith a th ic k n e s s o f 300
m eters . I t i s c o r r e la te d w ith th e Naco form ation in sou th ern A rizona by
T a lia fe r r o (1 9 3 3 ). At C abullona, i t i s a grey lim esto n e 750 m eters th ic k
r e s t in g on a sed im en tary sequence o f Lower P a le o z o ic rocks ( F r ie s , 1 9 6 2 ).
In th e T ig re a r e a , a sequence o f compact lim esto n e and c la y w ith c h e r t ,
rep o rted by Imlay (1 9 3 9 ) , b e lo n g s to t h i s system .
20
Perm ian. In th e A lta r , H e rm o sillo , and El T igre d i s t r i c t s , rocks
o f Permian age ou tcrop . In th e v i c i n i t y o f A lta r and A ntim onio, th ey
c o n s is t o f in t r u s iv e rock s a t th e b a se , w ith san dston e and sh a le and a
f o s s i l i f e r o u s , b lu e -g r e y lim e sto n e a t th e to p , w ith a th ic k n e s s o f 160
m eters (Cooper and A r e lla n o , 1 946 ). W ithin th e H erm osillo d i s t r i c t , a t
th e Cerro de C obachi, a sed im entary sequence o f g r e a t r e e f s o f w h ite and
b lu e m assive c r in o id a l lim e s to n e s , w ith a th ic k n e ss o f 550 m eters i s
co n sid ered by King (1939) to b elon g to t h i s p e r io d . In th e T igre a rea ,
Imlay (1939) r e c o g n iz e s a s e c t io n o f g rey -w h ite lim esto n e w ith in c lu s io n s
o f c h e r t and 1 ,8 0 0 m eters in th ic k n e s s as Permian.
M esozoic
M esozoic rock s are exposed e x t e n s iv e ly through th e s t a t e o f
Sonora, b u t are more abundant in th e c e n tr a l p a r t , w ith in th e P a r a l le l
Ranges and V a lle y Subprovince. They are a lso exposed in th e e a s te r n
Sonoran D eser t P ro v in ce , bu t th ere th ey are l e s s abundant. In th e
P a r a l le l Ranges and V a lle y s S ubprovince, rocks o f t h i s age are rep re
sen ted c h ie f ly by c o n t in e n ta l d e p o s it s , w h ile in th e Sonoran D esert
P rovince th ey are c h ie f l y m arine d e p o s it s . The th ic k n e s s in c r e a s e s from
1 ,100 m eters on th e w est to 2 ,3 0 0 m eters (K ing, 1 9 3 9 ), or perhaps to
3 ,0 0 0 m eters ( F r ie s , 1962) in th e e a s t . F o s s i l ev id en ce i s th e b a s is fo r
age d eterm in a tio n in th e s e sy stem s.
T r ia s s ic - J u r a s s ic . The c h a r a c t e r i s t ic s t r a t ig r a p h ic u n it o f t h i s
age i s th e Barranca Form ation — Upper T r ia ss ic -L o w er J u r a s s ic . I t was
named, by Dumble (1 9 0 0 ) , f o r e x c e l le n t exposures in th e v i c i n i t y o f th e
Barranca San X avier a r e a , 100 k ilo m e te r s so u th e a s t o f H e rm o sillo . H ere,
21
th e form ation i s composed o f c l a s t i c rocks w ith some beds o f c o a l and
g r a p h ite . Rocks th a t have been c l a s s i f i e d as Upper T r ia ss ic -L o w er
J u r a s s ic are exposed w ith in n orth ern and sou thern Sonora.
In n orth ern Sonora, a t th e A ntim onio Mine, 30 k ilo m e te r s w est o f
Caborca (K ing, 1 9 3 9 ), and in th e v i c i n i t y o f Benjamin H i l l (F lo r e s , 19 2 9 ),
th ey are rep re se n ted by a sed im en tary sequence o f sa n d sto n e , s h a le and
lim esto n e 1 ,200 m eters th ic k .
In sou th ern Sonora, King (1939) and F lo res (1929) r e c o g n iz e rocks
correspon d in g to t h is age in th e Yaqui R iver V a lle y and in th e S ie r r a de
M o ra d illa s . In th e Yaqui R iver V a lle y , th ey are composed o f m assive
san d ston es c o n ta in in g a r g i l la c e o u s h o r iz o n s and s e v e r a l la y e r s o f
g ra p h ite ; th e exposed th ic k n e s s i s about 450 m e te r s . W ithin th e S ie r r a
de M o r a d illa s , 50 k ilo m e te r s sou th w est o f H e rm o sillo , th ey c o n s is t o f
g r a p h it ic q u a r tz it e s and in d u ra ted san d ston es w ith a th ic k n e s s o f 1 ,450
m eters.
V o lca n ic rocks o f T r ia s s ic - J u r a s s ic age have been mapped and
dated in sou th ern A rizona betw een m erid ians 110° and 111°. They co n tin u e
in to Sonora, where th ey reach a th ic k n e ss o f 3 ,0 0 0 m eters (H ayes, 1966).
C reta ceo u s . Lower and Upper C retaceous rocks are rep re se n ted by
sed im en tary , v o lc a n ic , and in t r u s iv e ro ck s. The Lower C retaceous rocks
crop ou t e x t e n s iv e ly throughout th e s t a t e o f Sonora, w h ile Upper C reta
ceous rocks are r e s t r i c t e d to th e n o r th ea stern p a r t o f th e s t a t e .
1. Sedim entary rock s: A ccording to King (1 9 3 9 ) , th e b e s t exp osu res
o f Lower C retaceous sed im en ts are in th e Sahuaripa D i s t r i c t
betw een Sahuaripa and Yaqui R iv ers . H ere, th ey c o n s is t o f a
22
sequence o f th in -b ed d ed q u a r t z i t e s , m assive b lu e l im e s to n e ,
sa n d sto n e , and m assive conglom erate w ith a th ic k n e s s o f 3 ,5 0 0
m eters . King c o r r e la t e s t h i s s e c t io n w ith th e B isb ee group o f
sou th ern A rizona and w ith th e 900-m eter s e c t io n d esc r ib e d by
Im lay (1939) n ear th e E l T ig re a rea . Imlay (1939) r e c o g n iz e s th e
Glance and M orita Form ations which ex ten d southward from th e
B isb ee D i s t r i c t in to sou th ern Sonora in th e S ie r r a de lo s A jo s,
where th ey reach a th ic k n e s s o f 2 ,4 0 0 m eters . F lo res (1929) con
s id e r s th a t a s e r ie s o f lim esto n es and s h a le s n ear Santa Ana
co n ta in s c h a r a c t e r i s t ic fauna n o t o ld e r than A ptian age.
Upper C retaceous rocks are o n ly exposed a t th e C abullona
B asin and appear to o v e r l ie th e Lower C retaceous unconform ably
(T a lia fe r r o , 1 933 ). They c o n s is t o f i n t e r s t r a t i f i e d v o lc a n ic
c l a s t i c sed im en ts w ith a th ic k n e s s o f 2 ,8 0 0 m eters .
2 . V o lca n ic r o c k s : King (1939) co n s id e r s th a t two p e r io d s o f
C retaceous vo lca n ism took p la c e in sou th w estern U n ited S ta te s and
n orth w estern M exico. The f i r s t i s exposed in th e Sahuaripa
D is t r i c t and th e second in th e C abullona a rea . At b oth l o c a l i t i e s
th ey c o n s is t o f a n d e s i t ic f lo w s and t u f f s in terb ed d ed in th e
f o s s i l i f e r r o u s sed im entary ro ck s . At Sahuaripa, th e y are dated
as Lower C retaceous and in th e C abullona area as Upper C retaceou s.
A lso , King co n s id e r s th a t a l l th e o ld e r v o lc a n ic rock s in th e
B asin and Range Subprovince are probab ly o f Lower C retaceou s age
b eca u se , so f a r , no f o s s i l s have been found. King (1939) and
W lsser (1966) s t a t e th a t th e C retaceous v o lc a n ic sequence
in c r e a s e s toward th e w est where th e s e c t io n i s composed a lm ost
w h o lly o f v o lc a n ic ro ck s .
3 . I n tr u s iv e rock s: The age o f th e in t r u s iv e rock s have been much
d ebated . King (1939) co n sid ered th e m a jo r ity o f th e p lu to n s in
c e n tr a l-so u th e r n Sonora as M iddle T e r t ia r y in age. However, in
view o f la t e r i s o t o p ic age d eterm in a tio n s and s tr a t ig r a p h ic
f e a t u r e s , i t seems l i k e l y th a t th e m a jo r ity o f th e p lu to n s are
l a t e C retaceou s-E arly T e r t ia r y and correspond to th e Laramide
R ev o lu tio n .
Damon and Mauger (1966) and L iv in g sto n (1 9 7 3 ) , by ap p ly in g
i s o t o p ic age d e te r m in a tio n s , determ ined th a t th e m a jo r ity o f th e
in t r u s iv e s in sou th ern A rizona and n orth w estern Sonora, in th e
B asin and Range S ubprovince, correspond to th e in t e r v a l o f th e
Laramide Orogeny 52 to 72 my ago. Damon (1968) r e p o r ts a q u artz
m onzonite in t r u s iv e in th e A lt a r D i s t r i c t to be 105 my o ld .
W isser (1966; based on Damon and Bikerman, 1964) s t a t e s th a t th e
Capomaz q u artz m onzonite mass in n orth ern S in a lo a , 10 k ilo m e te r s
so u th o f Sonora, and s e v e r a l p lu to n s in n orth ern Sonora, f a l l
w ith in th e tim e range o f th e Laramide R ev o lu tio n .
W isser (1 9 6 6 ) , based on s t r a t ig r a p h ic e v id e n c e , such as a t El
T ig r e , G uayopita (Hovey, 1906) and P i la r e s (K ing, 1 9 3 9 ), su g g e s ts
a la t e C retaceou s-E arly T e r t ia r y age fo r th e in t r u s iv e b o d ie s .
At El T ig r e , g r a n ite below T e r t ia r y v o lc a n ic rock s in tr u d e s a
sequence o f lim esto n e and sh a le o f probably E arly C retaceou s age.
At G uayopita, in w estern Chihuahua, b a sa l T e r t ia r y r h y o l i t e
23
appears to r e s t on an eroded su r fa c e o f lim esto n e invaded by
g r a n it e . At th e P i la r e s Mine, 10 k ilo m e te r s e a s t o f N a co za r i,
g r a n ite in v a d es lim esto n e and probably i s p r e -T e r t ia r y in ag e .
F in a l ly , N is s e r (1966) em phasizes th a t , in th e w estern U nited
S t a t e s , m ajor p lu to n s correspond m ainly to M esozoic a g e , and th a t
M id -T ertiary p lu to n s are w ith few e x c e p tio n s s to c k s o f sm a ll
s i z e . I t seems l i k e l y th a t t h i s g e o lo g ic c o n d it io n may be
p r e se n t in th e s t a t e o f Sonora.
24
C enozoic
C enozoic form ation s co ver a la r g e p erce n ta g e o f th e s t a t e o f
Sonora. T e r t ia r y u n it s are composed c h ie f ly o f v o lc a n ic rock s and
c la s t ic - s e d im e n ta r y r o c k s . These u n it s are exposed p r in c ip a l ly w ith in
th e S ie r r a Madre O c c id en ta l P ro v in ce . I n tr u s iv e rock s o f C retaceou s-
T e r t ia r y and M id -T ertiary age have been rep o r te d . Q uaternary sed im entary
rock s are more w idespread w ith in th e Sonoran D esert P rov in ce and w ith in
th e C o a sta l P la in o f th e G ulf o f C a lifo r n ia , as shown in th e s t a t e
g e o lo g ic map (F igu re 5 , in p o c k e t ) .
T e r t ia r y . A ccording to King (1 9 3 9 ), e a r ly T e r t ia r y v o lc a n ic rocks
are re p r e se n te d by a group o f a n d e s it e s , r h y o l i t e f lo w s , t u f f s , and th ic k
c l a s t i c d e p o s it s . The group r e s t s unconform ably upon C retaceous ro ck s .
The same author s t a t e s th a t e a r ly T e r t ia r y v o lc a n ic rocks show a d i f f e r
en t com p osition from both C retaceous and la t e r T e r t ia r y v o lc a n ic ro ck s .
The e a r ly T e r t ia r y rock s are c h ie f ly a n d e s it ic w h ile la t e T e r t ia r y rocks
are c h ie f ly r h y o l i t i c in com p o sitio n . The e a r ly T e r t ia r y v o lc a n ic rock s
are b e s t d eveloped in th e Barranca s e c t io n where th e y reach a th ic k n e s s
25
o f 2 ,3 0 0 m e te r s . W isser (1966) tr a v e r se d s t r a t ig r a p h ic s e c t io n s a t many
l o c a l i t i e s in th e S ie r r a Madre O cc id en ta l P rov in ce . H is s e c t io n s show
th a t th e v o lc a n ic p i l e in th e P la te a u , B arranca, and B asin and Range
s e c t io n s c o n s is t m ain ly o f in te r m e d ia te to b a s ic flo w s o f p y r o - c la s t i c
rock s a t th e b a se ; w hereas th e top i s composed o f r h y o l i t i c t u f f s and
f lo w s w hich r e s t unconform ably upon th e low er r o c k s . Imlay (1 9 3 9 ) ,
F r ie s (1 9 6 2 ) , A lvarez (1 9 6 6 ), and th e C .R .N .N .R. (1970) rep o r t s im ila r
l i t h o l o g i c and s t r a t ig r a p h ic f e a tu r e s to th o se o f King and W isser .
T h erefo re , t h i s appears to be a c o r r e c t in t e r p r e ta t io n o f th e v o lc a n ic
p i l e o f th e S ie r r a Madre O c c id e n ta l.
As s t a t e d b e fo r e , e a r ly in t r u s iv e rocks o f Laramide age are
rep o r te d by Damon (1968) and Damon and Mauger (1966) and L iv in g sto n
(1 9 7 3 ). S om e.o f th e l o c a l i t i e s where th ey ou tcrop a re: La C aridad
D e p o s it , 54 my; San F e l ip e de J e s u s , 49 my (Damon, 1975); Cananea, 58 my
and 67 my; Aurora, 54 my; and Capomaz north S in a lo a , 58 my. I n tr u s iv e
rocks o f Eocene age are rep o r te d a t La F lo r id a -B a rr ig o h , 3 k ilo m e te r s
w est o f N acozari (Damon, 1975 ).
King (1939) co n s id e r s th a t th e v o lc a n ic p i l e w hich forms th e
S ie r r a Madre O cc id en ta l i s o f E arly T e r tia r y age. N e v e r th e le s s , W isser
(1 9 6 6 ) , based on a b so lu te age d eterm in a tio n s carred ou t by Damon e t a l .
(1 9 6 5 ) , con clu d es th a t T e r tia r y vo lca n ism s ta r te d in E ocen e-O ligocen e
t im e , reach in g i t s g r e a t e s t in t e n s i t y during O ligocene-M iocene tim e
( s im ila r to th e Pachuca D is t r ic t in c e n tr a l M ex ico ).
Late T e r t ia r y c l a s t i c sed im entary rocks are re p r e se n te d by th e
B au carit Form ation, named by Durable (1900) fo r exposures in th e v i c i n i t y
26
o f th e B a u ca r it tow n, sou th ern Sonora. The form ation h ere i s composed o f
sa n d s, c la y e y sa n d s , and conglom erates o f ex trem ely even b ed d in g . King
(1939) d e sc r ib e s t h i s form ation fa r th e r sou th o f B au ca r it where th e f o r
m ation i s b e s t exp osed . He d e sc r ib e s th e u n it as composed a t th e b ase o f
a b a s a l t i c member fo llo w e d by w ell-b ed d ed sa n d sto n e s , con glom erates and
some c la y s w hich were d er iv ed from th e o ld e r ro ck s . T h is form ation i s
c h ie f ly exposed w ith in grabens o f th e B asin and Range Subprovince. Damon
determ ines th e age o f th e low er b a s a lt member as 21 my in th e San F e lip e
de J esu s a rea , c e n tr a l Sonora (Damon, 1975). G a lb ra ith (1959) c o n s id e r s
th a t th e b a s a l t i c f lo w s o f th e P in a ca te a rea , n orth w estern Sonora, as
l a t e P l io c e n e . King (1939) e s t im a te s th a t b a s a l t i c f lo w s in c e n tr a l
Sonora are probab ly younger than th o se o f th e B au carit Form ation.
Q uaternary. Q uaternary sed im ents cover over o n e - th ir d o f th e
s t a t e o f Sonora. They are re p r e se n te d in p ed im en ts, a l l u v i a l fa n s , sa n d s ,
a l l u v i a l f i l l s , and g r a v e ls w hich cover th e low er p a r ts o f r iv e r s and
v a l l e y s .
The a l l u v i a l f i l l may a t t a in a th ic k n e s s as g r e a t as 180 m e te r s ,
as a t T ecorip a (K ing, 1 9 3 9 ), Agua P r ie ta , and N acozari v a l l e y s
(C .R .N .N .R ., 1 970 ). Most a g r ic u ltu r a l a c t i v i t y o f th e r e g io n ta k es
p la c e in th e sands and s i l t s o f th e a lluv iu m and e s p e c ia l ly in th e
C o a sta l P la in o f th e G ulf o f C a lifo r n ia .
S tr u c tu r e and S tr u c tu r a l H isto r y
A ll th e g e o lo g i s t s who have s tu d ie d th e g eo lo g y o f th e s t a t e o f
Sonora a g r e e , w ith few e x c e p t io n s , th a t th e landform s o f th e s t a t e are
in t im a te ly r e la t e d to th e u n d er ly in g ro c k s . T h ere fo re , th e s tr u c tu r a l
27
fe a tu r e s o f th e s t a t e are d e sc r ib e d , based upon th e geom orphic p ro v in ce s
and th e s t r a t ig r a p h ic column d e scr ib ed p r e v io u s ly .
Sonoran D eser t P rov in ce
W ithin t h i s p r o v in c e , most o f th e s tr u c tu r a l f e a tu r e s are covered
by r e c e n t sed im en ts . However, th e i s o la t e d r id g e s are in te r p r e te d by
Thom bury (1965) as u p l i f t e d b lo ck s bordered by normal f a u l t s in advanced
s ta g e s o f e r o s io n . King (1939) p o in ts ou t th a t th e ranges o f sed im en tary
and v o lc a n ic rock s appear to be r o o f pendants in a v a s t group o f g r a n i t i c
b a th o l i th s s tr o n g ly a f f e c t e d by e r o s io n .
W ithin th e n orthern p a r t o f th e p r o v in c e . O lder and Younger Pre-
cambrian and P a le o z o ic rock s are w id e ly exp osed . In th e c e n tr a l and
sou th ern p a r ts o f th e p r o v in c e , o n ly P a le o z o ic rocks ou tcrop ; Younger
Precambrian and P a le o z o ic rock s are unconform able (Cooper and A r e lla n o ,
1946; Damon, 19 6 8 ).
The O lder Precam brian rock s show a predom inant n o r th e a s te r ly
tren d o f bedding and f a u l t in g , w h ile th e Younger Precambrian rock s tren d
n o r th w e ste r ly (F r ie s , 1 962 ). T h is s t r u c tu r a l change in tr e n d , i s in t e r
p re ted by Damon (1968) to be a r e s u l t o f th e A rizonan R ev o lu tio n . F r ie s
(1962) r e p o r ts th a t P a le o z o ic rock s w ith in th e Sonoran D eser t P rov in ce
and th e B asin and Range Subprovince show th e same n o r th w e ste r ly r e g io n a l
s tr u c tu r a l tren d as th e Younger Precambrian r o c k s . The same au th or ,
based on th e s t r a t ig r a p h ic r e la t io n s h ip s o f P a le o z o ic and Precam brian
r o c k s , c o n s id e r s th a t n orth w estern Sonora was a c o n t in e n ta l p la tfo rm o r
m io g e o s in c lin e . He names t h i s s tr u c tu r e th e Sonoran B asin o f th e
C o rd ille r a n G e o s in c lin e o f North Am erica. The e x is t e n c e o f a
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e u g o e s in c l in a l f a c ie s in n orth ern Sonora i s su g g este d by De Cserna (1 9 6 0 ).
However, i t now appears th a t th e s t r a t ig r a p h ic fe a tu r e s do n o t support
h is t h e s i s .
S ie r r a Madre O c c id en ta l P rov in ce
The B asin and Range, Barranca, and P la tea u s e c t io n s which form
t h i s p ro v in ce are p a r a l l e l b e l t s whose s t r u c tu r a l fe a tu r e s tren d n orth
10° w est (A lv a r e z , 1966; K ing, 19 3 9 ).
B asin and Range S e c t io n . S tr u c tu r a lly , t h i s s e c t io n i s charac
t e r iz e d by a s e r i e s o f h o r s t s and grabens bordered by normal f a u l t s
(F r ie s , 1962; A lv a rez , 1 9 6 6 ). A lthough many f a u l t s in th e n orth ern p a r t
o f th e p ro v in ce are rep o rted as th r u s ts and o v e r th r u s ts (K ing, 1939;
W isser , 1966).
W ithin t h i s su b p ro v in ce , p r in c ip a l ly M esozoic and Cenozoi-c rocks
o u tcro p . The M esozoic rocks show th e same, n o rth -n o r th w estern s tr u c tu r a l
tren d o f f a u l t in g as p re-M eso zo ic rock s (F r ie s , 1962; K ing, 1939; W isser ,
1 9 66). F r ie s (1962) c o n s id e r s th a t during Permian to e a r ly - T r ia s s ic
tim e a t e c t o n ic e v e n t , th e Sonoran Orogeny, d estro y ed th e s tr u c tu r e o f
th e P a le o z o ic g e o s in c l in e . He c o r r e la te s th e Sonoran Orogeny w ith th e
A ppalachian Orogeny o f King (1 9 5 1 ) . A lvarez (1966) em phasizes th a t
during U p p e r -T r ia ss ic to L ow er-Ju rassic tim e c o n t in e n ta l d e p o s it s o f th e
Barranca Form ation w ith in th e Sonoran B asin were d e p o s ite d .
In la y (1939) p o in ts o u t t h a t , in th e v i c i n i t y o f E l T ig r e , n o r th
w estern Sonora, th e s tr u c tu r e s tren d w e s t-n o r th w e s te r ly . He s u g g e s ts
th a t t h i s s t r u c tu r a l fe a tu r e i s r e la t e d to th e C retaceous g e o sy n c lin e o f
n orth ern Sonora and sou th ern A rizon a . T a lia fe r r o (1933) a ls o r e p o r ts a
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s im ila r n o rth -n o r th w est tren d in th e C abullona area . King (1939) rec o g
n iz e s a M id-C retaceous orogeny o n ly in northernm ost Sonora. He c o n s id e r s
fo ld in g and f a u l t in g o f th e p r e -T e r t ia r y rocks o f n orth w est Sonora are
r e la t e d to th e Laramide Orogeny.
During th e Laramide R ev o lu tio n , th e m a jo r ity o f th e p lu to n s were
em placed, f o ld in g and u p l i f t in g th e p r e -T e r t ia r y rock s and form ing th e
h o r s ts and grabens t y p ic a l o f th e B asin and Range S e c t io n (W isser , 19 6 6 ).
During u p p e r -T er tia r y tim e , th e grabens (v a l le y s ) were f i l l e d by t e r r i g
enous m a te r ia ls and b a s a l t i c flo w s o f th e B a u ca r it Form ation (K ing,
1939; Damon, 1 975 ). The main system o f f a u l t in g tren d s n orth to n o rth
w est 10° (F r ie s , 1962; W isser , 1 966 ). N orth east t e n s io n a l fr a c tu r e s n or
mal to th e n orth w est system w ere formed (A lv a rez , 19 6 6 ).
Barranca S e c t io n . King (1939) r e p o r ts th a t th e system o f f a u l t s
in t h is s e c t io n tren d s a lm ost n o r th -so u th . They have r a is e d sed im entary
and in t r u s iv e p r e -T e r t ia r y rocks to th e zone o f e r o s io n . However, he con
s id e r s th a t e r o s io n , n o t s t r u c tu r e , i s th e most im portant d eterm inan t in
th e deep gorges o r b arran cas. The fa u lt in g i s normal and h ig h d ip p in g
(F r ie s , 1 962 ). Upper T e r t ia r y r h y o l i t e s are th e m ost abundant rocks
which dip from h o r iz o n ta l to 35° to th e n o r th e a s t (W isser , 1966 ).
P la tea u S e c t io n . W isser (1966) c o n s id e r s th a t th e main s tr u c
tu r a l fe a tu r e in t h i s s e c t io n i s a com plex e lo n g a te d u p l i f t th a t tren d s
n o r th w e ste r ly and c o in c id e s c l o s e l y w ith th e M esozoic o c c id e n ta l g e o a n t i
c l in e . T his u p l i f t i s co n sid ered to be o f t e c t o n ic , n o t e r o s io n a l ,
o r ig in . He c a l l s t h i s s tr u c tu r e th e "main w elt" and em phasizes t h is
s tr u c tu r e becau se o f th e a s s o c ia te d p re c io u s m etal m ining d i s t r i c t s a lon g
30
th e w e l t . F a u lts in t h i s s e c t io n are norm al, tren d in g n o r th -so u th , and
are o f r e l a t i v e l y s im p le s tr u c tu r e (K ing, 1 9 3 9 ). Exposed rock s c o n s is t
m ain ly o f T e r t ia r y a n d e s i t ic and r h y o l i t i c f lo w s which l i e h o r iz o n t a l ly ,
w ith e r o s io n a l and an gu lar u n con form ity , a cro ss th e a n d e s i t ic s e r i e s
(W isser , 1966 ).
CHAPTER 3
ALAMOS DISTRICT
G eneral Geology
Geomorphology
The Alamos Mining D is t r ic t l i e s in th e B asin and Range and
Barranca Suprovinces o f th e S ie r r a Madre O ccid en ta l P rov in ce d escr ib ed
by A lvarez (1966) and shown in F igure 3.
As d esc r ib e d p r e v io u s ly , th e B asin and Range Subprovince c o n s is t s
o f an e lo n g a ted b e l t , 80 to 110 k ilo m e te r s w id e , o f lo n g itu d in a l moun
ta in s w hich are sep a ra ted by in term ontane v a l l e y s . The average tren d o f
both fe a tu r e s i s N10°W. In th e Alamos M ining D i s t r i c t , t h i s b e l t i s o n ly
30 k ilo m e te r s w id e , and 10 k ilo m e te r s sou th i t ends a g a in s t th e C oasta l
P la in o f S in a lo a P ro v in ce . The lo c a l tren d o f m ountain ranges and
v a l le y s i s N8°W.
The topography in th e area i s rugged and d iv e r s e , ran g in g from
500 m eters in th e low er p a r t s . V a lle y de Alamos, to 1 ,800 m eters in th e
h ig h e s t . S ie r r a de Alamos (F igu re 7 ) . The v a l le y s are d ra in ed by th e
Mayo and Cedros r iv e r s and th e Cuchujaqui Arroyo and i t s t r ib u t a r ie s
which flow toward th e G u lf o f C a lifo r n ia . The d ra in age in th e d i s t r i c t
shows d e n d r it ic and r a d ia l p a t te r n s . The d e n d r it ic p a tte r n i s common in
th e low er p a r ts th a t g e n e r a lly co n ta in g r a n ite o u tcro p s; th e r a d ia l
p a tte r n i s p r e se n t around th e h igh m ountains th a t g e n e r a lly c o n ta in
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U ltx)
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v o lc a n ic o u tc r o p s . A lthough both ty p e s o f d ra in age are in f lu e n c e d p r i
m arily by s tr u c tu r a l f e a t u r e s , e r o s io n and sed im en ta tio n a ls o p la y an
im portant r o le in d eterm in in g th e p h y sio g ra p h ic e x p r e ss io n o f th e in t r u
s i v e , sed im en tary , and v o lc a n ic rocks exposed in th e d i s t r i c t .
King (1939 , pp. 1636-1637) d e sc r ib e s th e edges and v a l l e y s o f
th e Alamos D i s t r i c t as fo l lo w s :
Some o f th e th ic k r h y o l i t e f lo w s are cu t in to h ig h , sh eer p in n a c le s , as in th e S ie r r a de Alamos . . . The p lu to n ic rocks are g e n e r a lly eroded to low ped im ents . ♦ . The Rio Cedros fo llo w s th e n orth ern p o r t io n o f another v a l l e y . . ; E ast o f Alamos, th e southward c o n tin u a tio n o f t h i s v a l l e y i s a broad area o f low h i l l s and mesas . . . To the sou th . . . th e a l l u v i a l f l a t s o f th e C o a sta l P la in extend around and betw een th e m ou n ta in s.
S tr a tig r a p h y
In th e Alamos D i s t r i c t , th e exposed rocks range in age from
P a le o z o ic (?) to R ecen t. The s tr a t ig r a p h ic column in th e area i s la r g e ly
based upon work in sou thern Sonora by King (1939) and W isser (1 9 6 6 ) , and
upon th e r e l a t iv e s t r a t ig r a p h ic p o s i t io n o f th e exposed r o c k s . As
s ta t e d b e fo r e , no s tu d ie s o f age d e term in a tio n s were done during th e
f i e l d re c o n n a issa n c e .
W ithin th e mapped a rea , which covers 1^200 square k ilo m e te r s ,
th e r e are exp osu res o f m etam orphic, sed im en tary , in t r u s iv e , and v o lc a n ic
ro ck s . A g e n e r a l d e s c r ip t io n o f th e s tr a t ig r a p h y in th e Alamos D i s t r i c t
i s as shown in F igure 6 ( in p o c k e t ) .
P a le o z o ic ( ? ) . Even though no exp osu res o f P a le o z o ic rock s are
p lo t t e d in th e g e o lo g ic map o f th e Alamos D i s t r i c t , i t appears p o s s ib le
th a t rocks in th e v i c i n i t y o f P resa M ocuzari may be o f t h i s age . T h is
34
assum ption i s b ased on work by King (1 9 3 9 ), who r e c o g n iz e s t h a t , in th e
v a l l e y o f th e Mayo R iver , 7 k ilo m e te r s n o r th , some exposed rock s may be
P a le o z o ic (K ing, 1939, p . 1644): "Near th e Rio Cedros and t o th e w est o f
i t th e r e are lo c a l sm a ll ou tcrop s o f sed im entary r o c k s . . . . T h eir age
and s t r u c tu r a l r e la t io n s are u n c e r ta in , bu t i f th e sed im entary rocks n ear
th e Mayo and Cedros v a l l e y s are P a le o z o ic th e s e may a ls o b e ."
At Rio C edros, th e sed im en tary rock s are d esc r ib e d as l im e s to n e ,
red and w h ite q u a r t z i t e , and s l a t e . The lim esto n e co n ta in s c r in o id
stem s, c o r a ls , and b ra ch iop od s. The a ss ig n ed age o f th e s e rocks i s
Permian.
At th e P resa M ocuzari l o c a l i t y , th e rocks c o n s is t o f l im e s to n e ,
q u a r t z i t e , and s l a t e . I t i s e v id e n t th a t th e rocks are l i t h o l o g i c a l l y
s im ila r to th e P a le o z o ic rock s o f th e Cedros and Mayo r i v e r s . However,
no f o s s i l s w ere re c o g n iz e d during th e g e o lo g ic rec o n n a issa n ce due to
the in te n s e metamorphism th a t a f f e c t e d th e ou tcrop p in g ro ck s .
M esozoic. M esozoic rocks are exposed in r e l a t i v e l y sm a ll area s
in th e Alamos D i s t r i c t and are c o n s id era b ly metamorphosed. They co v er
about f i v e p e r c e n t o f th e a rea . The age o f th e rock s correspond to th e
Upper T r ia ss ic -L o w e r J u r a s s ic and C retaceous sy stem s.
1. Upper T r ia ss ic -L o w e r J u r a s s ic : W ithin th e area s tu d ie d , th e
c h a r a c t e r i s t ic s t r a t ig r a p h ic u n it o f t h i s age i s th e Barranca
Form ation. T h is u n it i s exposed in th e v i c i n i t y o f P ied ra s
Verdes town. H ere, th e form ation i s a lm ost w h o lly non-m arine and
i t c o n s is t s o f red q u a r t z i t e , q u a r t z i t i c sa n d sto n e , s l a t e , and
s e r i c i t i c s c h i s t . The w hole sequence shows a s tr o n g s e t o f
35
j o in t s which makes th e o r ig in a l bedding d i f f i c u l t to id e n t i f y .
The approxim ate th ic k n e s s o f th e form ation i s 150 m e te r s . The
m etased im ents form a c h a r a c t e r i s t ic e a s t -w e s t range o f h i l l s 5
k ilo m e te r s lo n g . They are in tru d ed to th e n orth and th e sou th by
q u artz d io r i t e and g r a n ite , r e s p e c t iv e ly (F ig u re 8 ) .
2 . C retaceou s: The C retaceou s system in th e Alamos D i s t r i c t i s
. r ep re se n ted by sed im en tary , v o lc a n ic , and in t r u s iv e r o c k s . They
a re w id e ly exposed through th e area and are o f p r in c ip a l impor
ta n ce b ecau se th e y co n ta in much o f th e known m in e r a liz a t io n
p r e s e n t in th e r e g io n .
a . Sedim entary ro ck s: King (1939) c o n s id e r s th a t th e Upper
C retaceous sed im en ts are r e s t r i c t e d to th e n orth ern p a r t o f
th e s t a t e . T h ere fo re , th e sed im entary rocks in th e more
so u th e r ly Alamos D i s t r i c t are co n sid ered o f Lower C retaceous
in a g e .
C retaceous s t r a t a are rep re se n ted by m assive and by bedded
l im e s to n e s . The m assive ty p e i s composed o f a v ery com pact,
d en se , grey lim esto n e which commonly shows r e c r y s t a l l i z a t io n ,
m a r b liz a tio n or s i l i f i c a t i o n n ear th e g r a n i t i c o r a n d e s i t ic
in t r u s iv e s . Some o f th e l o c a l i t i e s where th e se c h a r a c te r is
t i c lim e sto n e s are exposed are M ocuzari V i l la g e , Rancho
A rgen tin a , Rancho Tres M arias, and P ied ras Verdes town.
The bedded lim esto n e i s composed o f a f in e -g r a in e d , l i g h t
g rey lim e s to n e . The beds vary from 50 to 80 cm in th ic k n e s s
and co n ta in some i n t e r s t r a t i f i e d a n d e s i t ic f lo w s and v o lc a n ic
36
F igure 8. Exposure o f the B arranca Form ation (Upper T ria ss ic -L o w er J u r a s s ic ) in th e P ie d ra s Verdes Area. - - View look ing n o r th .
37
d e t r it u s o f 60 to 90 cm in th ic k n e s s . The u n it s show an
approxim ate th ic k n e s s o f 250 m e te r s , s t r ik in g from 10 to 20°
n o r th e a s t and d ip p in g from 50 to 60° so u th e a s t . These s t r u c
tu r a l fe a tu r e s were rec o g n ized a t S ie r r a de Alamos, one
k ilo m e te r sou th o f th e Q uintera Mine.
b . V o lca n ic r o c k s : V o lca n ic rock s o f p o s s ib le Lower C retaceous
age are exposed a t some p la c e s in th e S ie r r a de Alamos. They
c o n s is t o f green a n d e s i t ic f lo w s in terb ed d ed w ith v o lc a n ic
agglom erates w hich l i e unconform ably on p a r t ia l l y eroded
lim esto n e and are in tru d ed by g r a n ite a t t h e ir b a se . The
th ic k n e s s o f th e v o lc a n ic u n it i s unknown because o f th e
T e r t ia r y a n d e s i t ic rocks which o v e r l ie t h i s u n i t . No sep ara
t io n betw een th e two a n d e s i t ic rock s was done in r e c o n n a is
san ce work. For con v en ien ce , th e v o lc a n ic C retaceous rock s
were grouped w ith th e Laramide rocks exposed in th e c e n tr a l
p a r t o f S ie r r a de Alamos.
c . I n tr u s iv e ro ck s: As s ta t e d b e fo r e in Chapter 2 , i s o t o p ic age
d eterm in a tio n s (Damon and Mauger, 1966; L iv in g s to n , 1973) and
s t r a t ig r a p h ic ev id en ce (W isser , 1966) in d ic a te th a t th e
m a jo r ity o f th e in tr u s io n s in th e B asin and Range Subprovince
are o f Laramide age (52 to 72 m y). T h ere fo re , th e in t r u s iv e
rock s th a t are exposed in th e d i s t r i c t are co n sid ered con
temporaneous w ith th e Laramide ev en t due to th e s im ila r
g e o lo g ic ev id en ce m entioned b e fo r e .
38
The Laramide in t r u s iv e rocks in th e Alamos D i s t r i c t are
rep re se n ted by a g r a n i t i c b a th o lith and by a s to c k o f
p o r p h y r it ic a n d e s ite .
The g r a n i t i c b a th o lith i s w id e ly exposed throughout th e
d i s t r i c t and covers tw enty p erce n t o f th e a rea . I t i s p a r t
o f th e basem ent on which th e T e r t ia r y v o lc a n ic rock s were
la id down (W isser , 1 966 ). The g r a n i t i c mass shows magmatic
d i f f e r e n t ia t io n to g r a n o d io r ite -q u a r tz d io r i t e in th e v i c i n i t y
o f P ied ra s Verdes town and P resa M ocuzari. M oreover, i t
shows a d i f f e r e n t m in e r a lo g ic a l com p osition in the S ie r r a de
Alamos and in th e surrounding area . At S ie r r a de Alamos, th e
g r a n ite i s composed la r g e ly o f q u artz and fe ld s p a r , and in
th e v a l l e y i t shows a s u b s ta n t ia l amount o f m ica. F lo res
(1929) c o n s id e r s th e m ica -b ea r in g g r a n ite to b elo n g to an
o ld e r group, and th e q u a r tz - fe ld s p a r g r a n ite to be younger.
However, f i e l d o b se r v a tio n s appear to in d ic a te th a t t h i s
d if f e r e n c e in l i t h o lo g y i s due t o a r e g io n a l zon ing during
th e emplacement o f th e g r a n it ic in tr u s io n .
The s to c k o f p o r p h y r it ic a n d e s ite (E arly T e r tia r y ) i s
exposed in th e c e n tr a l p a r t o f S ie r r a de Alamos and covers
rou gh ly f i v e p e r c e n t o f th e mapped area . The body in tr u d e s
th e g r a n i t i c b a th o l i th and in c lu d e s fragm ents o f v o lc a n ic
agg lom erates w hich p rob ab ly were in co rp o ra ted a t th e tim e o f
th e in tr u s io n . B ecause o f th e f in e p o r p h y r it ic te x tu r e and
s t r u c tu r e , th e a n d e s i t ic mass i s co n sid ered to be a h yp ab yssa l
39
in t r u s io n . There are a ls o a n d e s it ic d ik es o f s im ila r te x tu r e
w hich cu t th e g r a n i t i c mass s t r ik in g N 2 0 -40° W.
I t m ust be p o in te d out th a t t h i s a n d e s it ic s to c k i s o f
c o n s id e r a b le im portance becau se o f s i l v e r - l e a d m in e r a liz a t io n
which i s p r e se n t as v e in s w ith in th e a n d e s ite or in co n ta c t
w ith th e g r a n ite or lim e sto n e .
C en ozo ic . C enozoic rocks are th e most abundant in th e d i s t r i c t
and cover over t h ir t y p e r c e n t o f th e area . They r e s t unconform ably on
C retaceous and o ld e r rock s and c o n s is t o f M id d le -T ertia ry v o lc a n ic r o c k s ,
Upper T e r tia r y c l a s t i c r o c k s , and Q uaternary ro ck s .
1. M iddle T e r tia r y : As was ex p la in e d in Chapter 2 , King (1939) and
W isser (1966) agree th a t w ith in th e S ie r r a Madre O cc id en ta l
P rovince th e c r i t e r i a fo r d i f f e r e n t ia t in g betw een th e T e r t ia r y
v o lc a n ic rocks i s based upon th e com p osition o f th e v o lc a n ic
f lo w s . The you n gest T e r t ia r y v o lc a n ic rocks are c h ie f ly ande
s i t i c , w hereas th e o ld e s t T e r t ia r y v o lc a n ic rock s are c h ie f l y
r h y o l i t i c in com p o sitio n . King (1939) co n s id e r s th a t T e r t ia r y
v o lca n ism corresponds to P aleocen e-E ocene tim e . W hile W isser
(1 9 6 6 ) , based on i s o t o p ic age d e te r m in a tio n s , con clu d es th a t
T e r t ia r y v o lcan ism corresponds to O ligocene-M iocene tim e . In
t h i s p ap er , th e T e r t ia r y v o lc a n ic rock s exposed in th e Alamos
D is t r i c t are co n sid ered M id d le -T ertia ry in a g e , in agreem ent w ith
W isser1s s t u d ie s .
The o ld e s t T e r t ia r y v o lc a n ic rock s (O lig o cen e) in th e area
s tu d ie d are r e p r e se n te d by a n d e s it ic la v a s , v o lc a n ic agg lom erates
and t u f f s o f th e same a n d e s i t ic com p osition which ou tcrop
ir r e g u la r ly throughout th e d i s t r i c t . They g e n e r a l ly s t r i k e ,
ex ce p t where th e r e are fo ld e d b lo c k s , from N 20° W to N 10° E and
d ip from 10-20° to th e e a s t and from 10-25° to th e so u th ,
r e s p e c t iv e ly .
The .you n gest T e r t ia r y v o lc a n ic rock s in th e a rea (M iocene)
are f lo w s and t u f f s o f r h y o l i t i c co m p o sitio n . They are exposed
g e n e r a l ly in th e h ig h e s t p a r ts o f th e a r e a , such as a t S ie r r a de
Alamos and Cerro Cacharamba, form ing sh e e r escarpm ents. The
s t r ik e and d ip o f th e se r h y o l i t i c f lo w s are s im ila r to th a t o f
th e a n d e s i t ic f lo w s .
2 . Upper T e r t ia r y : Upper T e r t ia r y rocks in th e d i s t r i c t are rep re
sen ted by th e B a u ca r it Form ation w hich i s exposed w ith in th e
grabens and low p a r ts o f th e area . In th e graben o f Arroyo de
Alam os, th e form ation i s composed a t th e b ase o f in te r m e d ia te
th in v o lc a n ic f lo w s in terb ed d ed w ith con glom erate. The upper
p a r t i s composed o f a th ick -b ed d ed m assive conglom erate o f a c id ic
and b a s ic ign eou s ro c k s . The th ic k n e s s o f th e form ation v a r ie s
from 30 t o 50 m eters (K ing, 1939) and shows a s t r ik e N 15 -10° W
and a d ip from 10 to 20° NE, which are s im ila r to th e r e g io n a l
s tr u c tu r a l system o f f a u l t in g . The form ation l i e s w ith angu lar
unconform ity upon th e o ld e r T e r t ia r y v o lc a n ic r o c k s . A ccording
to i s o t o p ic age d e term in a tio n s (Damon, 1 9 7 5 ), and f o s s i l ev id e n c e
40
(K ing, 1 9 3 9 ), th e B au carit Formation i s o f M iddle t o Upper
Miocene in age.
3. Q uaternary: Quaternary sed im ents cover about f i f t e e n p e r c e n t o f
th e mapped area . They are rep re se n ted by g r a n it i c pedim ents and
r e s id u a l s o i l s around th e S ie r r a de Alamos and a l l u v i a l fan s and
sands in th e Mayo R iver and secondary stream s.
Most a g r ic u ltu r a l a c t i v i t y in th e d i s t r i c t i s in th e r e s id u a l
s o i l s o f th e g r a n i t i c b a th o l i th and in th e sands a lon g th e
strea m s.
S tr u c tu r e
The s tr u c tu r a l fe a tu r e s o f th e Alamos M ining D i s t r i c t are c lo s e ly
r e la t e d to th e geom orphic u n it s in which th ey l i e , th e B asin and Range
and Barranca s e c t io n s o f th e S ie r r a Madre O ccid en ta l P ro v in ce , and th e
C oasta l P la in o f S in a lo a P rov in ce .
As e x p la in e d e a r l i e r , th e B asin and Range Subprovince c o n s is t s o f
a s e r i e s o f p a r a l l e l m ountains and v a l le y s which show an average tren d
N 10° W. W ithin th e Alamos D i s t r i c t , th e se r id g e s are bordered by s te e p
normal f a u l t s , w hich form th e r e g io n a l s tr u c tu r a l system o f f a u l t in g ,
s t r ik in g N 5 -3 0 ° W and d ip p in g N 7 5 -85° E (K ing, 1939 ).
From th e S ie r r a de Alamos to th e C o a sta l P la in o f S in a lo a in th e
w e st , th e r e are a number o f p a r a l l e l ra n g es , sep a ra ted by d e p r e s s io n s ,
some o f which are d o w n -fau lted a r e a s . But o th e r s , p erh a p s, are th e
r e s u l t o f d o w n -fa u lt in g . The r id g e s are composed o f v o lc a n ic f lo w s w hich
dip 20 to 30° to th e e a s t (F igu re 9 ) . Toward th e sou th o f S ie r r a de
41
I
Figure 9 . Ridge o f T e r tia r y R h y o lit ic Flows Dipping 25° to th e E ast. - - View look in g sou th .
43
Alamos, most o f th e ranges d isa p p ea r beneath th e a llu v iu m o f th e C oasta l
P la in o f S in a lo a , p o s s ib ly due to th e southward p it c h o f th e s tr u c tu r a l
fe a tu r e s (K ing, 1939 ).
L o c a lly , th e main fr a c tu r in g in th e d i s t r i c t i s tren d in g from
N 20 to 55° E and i s normal to th e r e g io n a l system o f f a u l t in g . The
m a jo r ity o f th e m in e r a liz e d v e in s w ith in th e d i s t r i c t are lo c a l iz e d
w ith in th e s e fr a c tu r e s (V azquez, 19 7 3 ).
T h ru stin g in th e area i s r ep re se n ted by f a u l t s tren d in g from
N 10 to 25° W and d ip p in g N 18 to 27° E. P ost m in e r a liz a t io n f a u l t s
which d isp la c e d th e v e in s are a ls o p r e s e n t . The d isp la cem en ts a lon g th e
v e in s v a r ie s from some c en tim e ters to two m eters . These s tr u c tu r a l
fe a tu r e s were rec o g n ized p r in c ip a l ly during underground mapping.
King (1939) c o n s id e r s two im portant u n co n fo rm itie s in th e area .
F ir s t , th e C retaceous unconform ity betw een th e E arly T e r t ia r y v o lc a n ic
rocks and th e C retaceous g r a n i t i c and a n d e s i t ic in t r u s io n s . Second, th e
T e r t ia r y unconform ity betw een th e Middle T e r t ia r y v o lc a n ic rock s and th e
Upper T e r t ia r y c l a s t i c rocks (B a u ca r it F orm ation). Both u n co n fo rm itie s
were rec o g n ized during th e f i e l d r e c o n n a issa n c e , bu t th ey w ere n o t mapped
in d e t a i l .
W isser (1966) d e sc r ib e s th e s tr u c tu r e o f th e d i s t r i c t as King
d o es , bu t he in c lu d e s new id e a s which m ight e x p la in th e o r ig in and s t r u c
tu re o f the ep ith erm al p r e c io u s-m e ta l p ro v in ce o f n orth w estern M exico:
They are:
1. The g r e a t p i l e o f th e T e r t ia r y v o lc a n ic rock s from w hich e r o s io n
has carved th e S ie r r a Madre O c c id e n ta l.
44
2 . The basem ent upon w hich th e v o lc a n ic rock s- were la id down
( in c lu d in g a l l - r e -T e r t ia r y r o c k s ) .
3 . The "main w elt" which l i e s in th e P la tea u s e c t io n o f th e S ie r r a
Madre O c c id e n ta l.
Based upon W isser ’s c o n c e p ts , th e basem ent in th e Alamos D i s t r i c t
i s composed o f th e T r ia s s ic - J u r a s s ic Barranca Form ation, th e C retaceous
l im e s to n e s , th e Laramide g r a n it ic b a th o lith and th e Laramide a n d e s it ic
in tr u s io n . W isser p o in ts ou t t h a t , in most c a s e s , th e d e p o s it o f p r e
c io u s m eta ls l i e w ith in th e T e r t ia r y v o lc a n ic p i l e , b u t , where th e v o l
c a n ic p i l e was t h in , th e p re c io u s m eta ls were d ep o s ite d c lo s e to o r
e n t ir e ly w ith in th e basem ent as in th e Alamos, La Dura, Lampazos and San
X avier d i s t r i c t s . These d i s t r i c t s l i e in a secondary "w elt" th a t tren d s
p a r a l l e l to the main w e l t . The "main w e lt ," a s tr u c tu r a l u n it 900
k ilo m e te r s lo n g , lo c a te d 40 k ilo m e te r s e a s t o f th e Alamos d i s t r i c t in th e
P la tea u S e c t io n o f th e S ie r r a Madre O ccid en ta l P ro v in ce , i s o f v i t a l impor
tan ce b ecau se o f th e p e r s i s t e n t p r e c io u s-m e ta l m in e r a liz a t io n a lon g i t .
The v e in s in th e Alamos D i s t r i c t tren d normal to th e a x is o f th e main
w e lt s im ila r to th e v e in s in th e T opia and Copala d i s t r i c t s in n orth ern
S in a lo a (F igure 1 0 ) .
A lso , accord in g to W isser (1 9 6 0 ), i t i s l i k e l y th a t th e Alamos
M ining D i s t r i c t l i e s in th e c e n tr a l p a r t o f an e lo n g a te d dome which was
formed by v e r t i c a l r a th e r than la t e r a l t e c t o n ic s . L o c a lly , th e S ie r r a da
Alamos shows a r a d ia l p a tte r n o f fr a c tu r e s w hich su g g e s ts a domal
s tr u c tu r e .
E X P L A N A T I O N
ZOO Km
ALAMOS MINING
DISTRICT
source Wi sser , 1966
F ig u re 10. L o c a tio n o f P re c io u s -M e ta l D i s t r i c t s a lo n g th e "M ain W elt"S t r u c t u r e in th e S i e r r a Madre O c c id e n ta l P ro v in c e .
46
Economic Geology
Ore C ontrol
W ithin th e Alamos M ining D i s t r i c t s t r u c tu r a l and l i t h o l o g i c a l
c o n d it io n s appear to have been th e c h ie f fa c to r s th a t c o n tr o lle d th e
c ir c u la t io n o f hydrotherm al f lu id s th a t produced o re .
S tr u c tu r a l C o n d itio n s . Based upon f i e l d mapping e v id e n c e , i t was
determ ined th a t s tr u c tu r e was th e main c o n tr o l in m ineral d e p o s it io n .
N in ety p e r c e n t o f th e ore d e p o s its in th e d i s t r i c t correspond to v e in
f i l l i n g f r a c tu r e s , and 55% o f th e v e in s show a p r e fe r r e d o r ie n ta t io n o f
N 20-65° E, normal to th e r e g io n a l system o f f a u l t in g . A lso , 27% o f th e
m in era lize d v e in s show an o r ie n ta t io n N 15-70° W, which i s th e r e g io n a l
s tr u c tu r a l tren d o f f a u l t in g . The rem ainder o f th e v e in s show an o r ie n ta
t io n E-N or N -s . A ll th e v e in s show a d ip betw een 60 and 85°.
Labounsky (1957) m entions th a t the f a u l t in g in th e sou th ern p a r t
o f S ie r r a de Alamos shows a g en era l fr a c tu r e p a tte r n th a t s t r ik e s N-W and
d ips N-E. To th e n o rth o f S ie r r a de Alamos, th e s t r ik e change to n o rth .
Labounsky (1957 , p . 6) em phasizes: " th is im portant change in th e d ir e c
t io n o f f r a c tu r in g . . . accounts fo r th e t e n s io n a l open ings [th e N-E
fr a c tu r e s ] which serv ed as ch an n els fo r m in era lize d s o lu t io n s to d e p o s it
m etal v a lu e s in th e v e i n - f i l l i n g f r a c tu r e s ."
The dynamic a c t i v i t y during m in e r a liz a t io n i s m a n ife s ted by
sh eared , b r e c c ia te d , and recem ented w a ll rock m a te r ia l w ith in th e v e in s .
I t seems l i k e l y th a t th e v e in m atter cou ld have been d e p o s ite d w h ile th e
w a lls o f th e v e in fr a c tu r e s were b e in g p u lle d a p a rt d u rin g th e l a s t s ta g e
o f th e M iddle T e r t ia r y v o lc a n ic a c t i v i t y .
47
L ith o lo g ic a l C o n d it io n s . L ith o lo g ic a l f a c to r s were an oth er impor
ta n t c o n d it io n th a t c o n tr o lle d th e ore d e p o s it io n in th e Alamos D i s t r i c t .
F ie ld rec o n n a issa n ce su g g e s ts th a t th e r e are two ty p es o f m in e r a lo g ic a l
a s s o c ia t io n s r e la t e d to l i t h o l o g i c a l c o n tr o ls . F i r s t , c o n ta c t m etasom atic
m in erals are re p r e se n te d by s c h e e l i t e , w o l la s t o n i t e , e p id o te , and g a r n e t ,
rep re se n ted by g r a n ite - l im e s to n e and a n d e s ite - lim e s to n e c o n ta c ts . Second,
ep ith erm al m in e r a ls , rep re se n ted by g a len a , s p h a le r i t e , a r g e n t i t e , t e t r a -
h e d r it e , and p y r it e are found m ain ly in th e p o r p h y r it ic a n d e s ite . To a
l e s s e r degree th ey are a ls o found in th e g r a n it ic b a th o lith and a t th e
g r a n ite -a n d e s it e c o n ta c t .
The r a t io o f m inera l abundance o f th e ep ith erm al m in era ls v a r ie s
co n s id e r a b ly w ith in th e v e in s . The v a r ia t io n in th e r a t io o f th e se
m in erals may be th e r e s u l t n o t o n ly o f m ineral zon ing but a ls o th e r e s u l t
o f co m p o sitio n a l d if f e r e n c e s in th e rocks through which s o lu t io n s
ascended.
In n orth w estern M exico, W isser (1966) c o r r e la te d v a r ia t io n s in th e
m ineralogy o f v e in s w ith th e h e ig h t above th e basem ent a t which th e
m in era ls were d e p o s ite d (F igu re 1 1 ) . W isser (1966 , p . 86) e x p la in s i t as
fo llo w s : "Although a number o f ore b o d ie s low in b a se s u l f id e s l i e s
f a i r l y c lo s e to th e basem ent, a l l d i s t r i c t s w ith heavy to m oderate amounts
o f b a se s u l f id e s l i e w ith in 500 m eters o f th e basem ent o r w h o lly w ith in
i t . "
In th e Alamos M ining D i s t r i c t , th e ore b o d ie s co n ta in heavy to
moderate amounts o f s u l f id e s and th ey l i e c lo s e to o r p r a c t i c a l ly w ith in
th e basem ent. T h ere fo re , i t i s b e l ie v e d th a t W isse r 's con cep t i s
SPARSE TO VERY SPARSEMODERATE TO SPARSEHEAVY TO MODERATEHEAVY
0 Au'Ag > l i 2CO1 Vertical range of ora
Source: Wisser, 19 6 6
F ig u re 11. Abundance o f B ase-M etal S u lf id e s P lo t te d A g a in st T h e ir H eight above Basement-Px00
49
in s tr o n g agreem ent w ith th e l i t h o l o g i c a l fe a tu r e s (basem ent) th a t con
t r o l l e d th e emplacement o f th e hydrotherm al m in e r a liz e d f lu id s .
Ore M ineralogy
The ore v e in s in th e Alamos D i s t r i c t co n ta in t y p ic a l ep ith erm al
m in erals a s s o c ia te d w ith m eta ls such as s i l v e r , le a d , z in c , and cop p er.
The prim ary m in era ls in th e ore b o d ie s are g a le n a , t e t r a h e d r i t e , argen
t in e , s p h a le r i t e , c h a lc o p y r ite , p y r i t e , and n a t iv e s i l v e r . Supergene
m in e r a liz a t io n i s r e p r e se n te d by a z u r i t e , m a la c h ite , c h r y s o c o lla ,
c e r a r g y r ite , g o e t h i t e , and n a t iv e s i l v e r . Gangue m in era ls in c lu d e q u artz
and, to a l e s s e r e x te n t , c a l c i t e and ch a lced ony . The chalcedony i s
u s u a lly p r e s e n t in geodes and open f r a c t u r e s . A ccessory m in era ls are
rep resen ted by c h lo r i t e , e p id o te and p r e h n ite . The ore w ith some v a r ia
t io n s in c o n c e n tr a tio n , i s m in e r a lo g ic a l ly v ery s im ila r among th e ore
b o d ies in th e d i s t r i c t .
Hydrothermal a l t e r a t io n in th e ep ith erm al ore b o d ie s i s r e p r e
sen ted by c h a r a c t e r i s t ic p r o p y l i t i c , s e r i c i t i c , and s i l i c i c m in era ls .
P r o p y l i t iz a t io n i s p r e se n t in a n d e s it ic w a ll rock s n ea r th e v e in -
f i l l e d f r a c t u r e s . The a l t e r a t io n i s e x te n s iv e but n o t p e r v a s iv e , and i t
exten d s from some c e n tim e te r s to a few m eters from th e v e in s . The charac
t e r i s t i c m in era ls are c h lo r i t e , e p id o te , c a l c i t e , and p y r i t e , p r e se n t as
v e in le t s and d is se m in a tio n s w ith in th e p o r p h y r it ic a n d e s i t ic ro ck s .
S e r i c i t i z a t i o n i s found p r in c ip a l ly in g r a n it i c rock s and some
tim es in a n d e s i t ic ro c k s . The s e r i c i t i c zone i s s p a t i a l l y more c l o s e l y
r e la te d to th e v e in s than th e p r o p y l i t i c zone. S e r i c i t i c a l t e r a t io n i s
50
rec o g n ized n ear i t s p a ren t fr a c tu r e s and i t ex ten d s from 10 to 40 c e n t i
m eters in to th e ro ck s .
S i l i c i f i c a t i o n i s found in both g r a n it ic and a n d e s i t ic rocks and
i s m o stly r e s t r i c t e d to i t s p aren t f r a c tu r e s . T his typ e o f a l t e r a t io n
c o n s is t s o f f in e -g r a in e d q u artz and chalcedony p r e se n t in v e i n l e t s and
d ru ses .
The ore w ith in th e d i s t r i c t ' s rep lacem ent d e p o s its i s composed o f
m etasom atic m in era ls such as g a r n e t, s c h e e l i t e , w o l la s t o n i t e , e p id o te ,
and d io p s id e . These m in era ls were formed by th e in tr u s io n o f th e g r a n ite
o r th e p o r p h y r it ic a n d e s ite n ear th e c o n ta c t w ith th e C retaceous
sed im en ts .
I t sh ou ld be m entioned th a t sed im entary d e p o s it s o f gypsum,
m a g n es ite , and lim esto n e a re a ls o p r e se n t w ith in th e d i s t r i c t . However, .
s in c e t h i s paper c o n s id e r s b a se and p r e c io u s m eta ls o n ly , th e in d u s t r ia l
m in era ls w i l l n o t be d is c u s se d .
M ineral P a ra g e n e sis and Zoning
M ineral P a r a g e n e s is . Based upon underground and su r fa c e mapping
in reco n n a issa n ce su r v e y s , i t appears th a t th e framework o f th e m in era l
iz a t io n sequence in th e Alamos D is t r ic t i s as fo llo w s :
1. The i n i t i a l ground p rep a ra tio n o f th e d i s t r i c t c o n s is te d o f f r a c
tu r in g , sh e a r in g , and f a u l t in g during th e emplacement o f th e Late
Laramide in t r u s iv e ro ck s . The f a u l t in g c r e a te d d i la t a n t a rea s o f
low p r e ssu r e and open sp ace fo r la t e r T e r t ia r y v o lc a n ic a c t i v i t y .
51
2 . F o llow in g f a u l t in g , th e open sp ace f a u l t s and sh ear zones were
invaded by magma a s s o c ia te d w ith th e v o lc a n ic rocks which were
la id down on th e p r e - e x i s t in g ro ck s .
3. The v o lc a n ic rocks were fa u lte d and t i l t e d as a r e s u l t o f th e up
l i f t o f th e S ie r r a Madre O c c id e n ta l, producing th e form ation o f
th e "main w e lt ." The f a u l t in g fo llo w ed th e same r e g io n a l system
o f f a u l t in g w ith in th e S ie r r a Madre P rov in ce (N 10° W). A lso ,
normal t e n s io n a l fr a c tu r e s s t r ik in g N-E were formed.
4 . P r o p y l i t ic , s e r i c i t i c , and s i l i c i c a l t e r a t io n m in era ls were
formed in th e w a lls o f f r a c tu r e s th a t serv ed as ch an n els fo r
m in e r a liz in g s o lu t io n s .
5 . Hydrotherm al s o lu t io n s invaded th e major open fr a c tu r e s in which:
a . The bu lk o f q u artz was d e p o s ite d e a r l i e r than o th e r m in e r a ls .
b . D ep o sits o f l e n t i c u la r and ta b u la r ore b o d ie s ca rry in g th e
bulk o f s u l f id e s were p r e c ip it a t e d .
c . I r r e g u la r d e p o s it s in broken zones ca rry in g n a t iv e s i l v e r and
copper w ere form ed.
d. O x id ation and le a c h in g o f s u l f id e s took p la c e .
An approxim ate m in e r a lo g ic a l seq u en ce , in th e Alamos D i s t r i c t ,
based upon f i e l d o b se r v a tio n s and upon th e normal d e p o s it io n o f ep ith erm a l
d e p o s its (W isser , 1966; Park and MacDiarmid, 1964) in th e P rec io u s M etal
P rovince o f M exico, i s shown in F igure 12.
M ineral Z oning. By a n a ly z in g th e d i f f e r e n t changes in ore and
gangue m in era logy among th e ore b o d ie s in th e area s tu d ie d , i t seem s
ORE PRIMARY SECONDARY
P y r ite -------
S p h a le r ite -
Galena
A r g e n tite
T e tr a h e d r ite
C h a lco p y r ite
S i lv e r
G oeth ite
M alach ite
A zu r ite
C h ry so co lla
C era rg y r ite
GAN CUE
Quartz ,
C a lc i te
C h lo r ite
Chalcedony
P reh n ite
F igure 12. P a r a g e n e tic Sequence fo r th e Alamos Mining D i s t r i c t .
S3
l i k e ly th a t th ree c a te g o r ie s o f m ineral zoning are rec o g n ized in th e
Alamos D is t r ic t : r e g io n a l zon in g , d i s t r i c t zo n in g , and ore body zon in g .
Very la r g e r e g io n a l zon in g i s a s s o c ia te d w ith th e p r e c io u s m eta l
m e ta llo g e n e t ic p ro v in ce o f c e n tr a l and n orth w estern M exico. As s ta te d
b e fo r e , th e changes in ore are r e la t e d to th e h e ig h t above th e basem ent
or d is ta n c e from th e so u rce (W isser , 1966). S o , th e h ig h c o n c e n tr a tio n s
o f s u l f id e s l i e c lo s e to th e so u r c e , whereas th e sp a rse c o n c e n tr a tio n s o f
s u l f id e s l i e fa r from th e sou rce (F igure 1 1 ).
D i s t r i c t and ore body zon ing are shown by th e c l o s e l y grouped
m ines a t S ie r r a de Alamos and surrounding a r e a s . Some o f th e m ines are
La Q u in tera , Prom ontorio, Santo Domingo, Zambona, and San Manuel
(F igu re 2 ) . W ithin th e se ore b o d ie s , a con sp icu ou s v e r t i c a l change in
m ineralogy i s n o ted . For in s ta n c e , th e Prom ontorio M ine, which l i e s in
th e sou th ern p a r t o f th e "Mother lode" s tr u c tu r e , shows a h ig h co n ten t
o f lea d and z in c . On th e o th e r hand, th e Q uintera M ine, lo c a te d in th e
c e n tr a l p a r t o f th e "Mother lode" v e in and 200 m eters h ig h e r , shows a
h igh co n ten t o f s i l v e r and q u artz (F igu re 1 3 ) . W ithout d ou bt, th e se
arrangem ents o f m in era ls su g g e s t a m in era l zon ing from th e su r fa c e
downward.
Ore G enesis
A ccording to i t s environm ent o f d e p o s it io n and m e ta llo g e n ic
com p osition , th e ore b o d ie s w ith in th e Alamos Mining D i s t r i c t are c l a s s i
f ie d in order o f im portance as ep ith erm a l, d issem in a ted , and pyrom eta-
som atic o re b o d ie s .
m e te r s above s e a level
m e te r s above sea level
Quintero
PromontoriesSanto
pomingo
Zambona
sen Manuel
- -200depth of mine within ore. bodyhor: scale
k ilom eters
F igu re 13. S e c t io n N 30° E Showing Changes in M ineralogy among Mines in th e S ie r r a de Alamos, Alamos D i s t r i c t . Cn
55
E pitherm al D e p o s its . W isser (1966) c l a s s i f i e s th e b a se -p r e c io u s
m eta ls p r e se n t in th e d i s t r i c t w ith in th e ep ith erm al p r e c io u s m eta ls
p ro v in ce o f n orth w est M exico. The common fe a tu r e s shared by a l l th e s e
d e p o s its w ith in t h i s p ro v in ce are:
1. A sso c ia t io n w ith v o lc a n ic r o c k s , p r in c ip a l ly a n d e s it e - r h y o l i t e
in th e e r o g e n ic r e g io n .
2. M iddle to Late T e r t ia r y age.
3 . V eins occupy fr a c tu r e s which are o f te n p re -m in era l f a u l t s .
4 . Hydrothermal a l t e r a t io n rep resen ted by p r o p y l i t i z a t io n , s e r i c i t i -
z a t io n , and s i l i c i f i c a t i o n .
5 . T e c to n ic movements which a c ted p a r a l l e l to th e fr a c tu r e w a lls
during v e in form ation .
6 . Quartz as th e p r in c ip a l gangue m ineral w hich u s u a l ly has been
d e p o s ite d e a r l i e r than th e b u lk o f s u l f i d e s .
7. O ccurrence o f s i l v e r in a r g e n t it e and in l e s s p ro p o rtio n g a le n a
and s p h a le r i t e .
8. The v e in te x tu r e shows b r e c c ia te d fragm ents cemented by v e in
m a tter .
9 . The ore body i s lo n g er on s t r ik e than on d ip . The ore zone has a
v ery d e f in i t e bottom . Below th e p r e c io u s m eta ls o r e , gangue and
b ase s u l f id e s m in era ls may p e r s i s t to th e low er l im i t o f
e x p lo r a t io n .
10. A ss o c ia t io n w ith lo c a l domes produced by fo r c e s a c t in g v e r t i c a l l y
n o t t a n g e n t ia l ly .
56
W isser (1966) a ls o s ta t e d th a t m e t a l l ic e lem en ts may have been
tra n sp o r ted to t h e ir p la c e o f d e p o s it io n by v o lc a n ic ga s-v a p o r
emmanations.
T h ere fo r e , comparing th e d e p o s it s in th e Alamos M ining D i s t r i c t
w ith th e c h a r a c t e r is t ic ep ith erm al fe a tu r e s d escr ib ed above, ex ce p t fo r
th e h yp abyssa l a n d e s i t ic in t r u s io n , i t i s concluded th a t th e v e in s p r e se n t
in th e d i s t r i c t l i e w ith in th e ep ith erm al c l a s s i f i c a t i o n o f ore d e p o s it s .
I t i s e s t im a te d th a t 80% o f th e p r o sp e c ts in th e area l i e w ith in
t h i s c l a s s i f i c a t i o n . Some o f th e more im portant o n e s , accord in g to
s tr u c tu r e , s i z e , mine c o n d it io n s , and a c c e s s i b i l i t y , are: Zambona, Santo
Domingo, Prom ontorio, Q u in tera , San Manuel, O ta te s , Plom osa, Ana M aria,
La R eina, V io le ta , and Japon en Mexico (F igure 14 , in p o c k e t ) .
D issem in ated D e p o s it s . P earce (1910) d e sc r ib e s th e P ied ras Verdes
Mine as a d issem in a ted ore body. In f i e l d rec o n n a issa n ce mapping, i t was
rec o g n ized th a t t h i s area shows many o f th e t y p ic a l f e a tu r e s d e sc r ib e d by
Schwartz (1966) and Bateman (1950) fo r t h is typ e o f d e p o s it , such as:
1. Low grade d e p o s it .
2 . A ss o c ia t io n w ith s t o c k - l ik e in tr u s io n s .
3. D issem in ated rep lacem ent in porphyry or in tru d ed s c h i s t .
4 . B lan k et sh ap e , g r e a te r h o r iz o n ta l than v e r t i c a l d im en sion s.
5 . S im ila r prim ary m in era logy .
6 . In te n se s e r i c i t i z a t i o n , in p la c e s , s i l i c i f i c a t i o n .
7 . O v erla in by leach ed cappings (F igu re 16, p . 5 8 ) .
More or l e s s supergene enrichm ent.8.
C onseq u en tly , i t seems l i k e l y th a t P e a r c e 's s ta tem en t i s t r u e ,
and th a t th e P ied ras Verdes area l i e s in th e ca teg o ry o f d issem in a ted
prophyry copper type (F igu re 1 5 ) . There a r e , in a d d it io n , some ep ith erm al
v e in s a s s o c ia te d w ith th e d issem in a ted m in e r a liz a t io n .
Pyrom etasom atic D e p o s it s . Pyrom etasom atic o r ign eou s metamorphic
d e p o s it s , accord in g to th e c l a s s i f i c a t i o n o f Park and MacDiarmid (1 9 6 4 ),
are a ls o p r e se n t in the Alamos D i s t r i c t . They are rep re se n ted by th e
c l a s s i c a l a s s o c ia t io n o f sed im entary and in tr u s iv e ro c k s . The sed im en ts
are lim esto n es o r s h a le , and th e in t r u s iv e rock s are g r a n ite o r q u a rtz -
d io r i t e .
A b r i e f d e s c r ip t io n o f th e p r o c e sse s o f th e pyrom etasom atic ore
b o d ies w ith in th e d i s t r i c t a re:
1. The ign eou s rocks r e c r y s t a l l i z e d th e lim esto n e to m arble.
2 . Hydrotherm al f lu id s coming from th e in t r u s iv e m asses formed lim e-
s i l i c a t e m in era ls such as g a r n e t , w o l la s t o n i t e , and d io p s id e .
3 . The in tr o d u c t io n o f m in e r a liz in g s o lu t io n s r ic h in tu n g sten took
p la c e , form ing f in e s c h e e l i t e c r y s t a ls w ith in th e t a c t i t e zone.
The pryom etasom atic p r o sp e c ts in the d i s t r i c t are La Esm eralda,
La M exicana, V ic to r ia , and Guadalupe I I . A ll show a s im ila r m in e r a lo g ic a l
a s s o c ia t io n .
D e sc r ip tio n o f Mines
A ccording to g eo g ra p h ic a l d is t r ib u t io n and analogous m in e r a lo g i
c a l , s t r u c t u r a l , and l i t h o l o g i c a l f e a tu r e s , th e ore b o d ie s in th e Alamos
Mining D is t r ic t may be grouped in s i x zones (F igu re 14):
57
58
Figure 15. Copper M in e r a l iz a t io n , B re c c ia t io n , and A r g i l l i c A l te r a t io n in the P ied ras Verdes Area. — The a rea su g g es ts a porphyry type d e p o s i t .
F igure 16. Capping and O xidation o f th e P ied ras Verdes P r o s p e c t . — View look ing e a s t .
59
1. S ie r r a de Alamos (Ag, Pb, Z n).
2 . S ie r r a la s Plomosas (Pb, Zn, A g).
3 . Lomas lo s Tanques (Cu, A u).
4 . S ie r r a d e l Chapote (Au, Cu, P b ).
5 . S ie r r a d e l B avispe (Cu, Au, A g).
6 . S ie r r a San Bernardo (Cu, A g).
As a lrea d y m entioned , th e main purpose o f t h i s stu d y i s th e
e v a lu a tio n o f l e a d - s i l v e r - z i n c d e p o s it s . On th e b a s is o f th e g e o lo g ic
e x p lo r a tio n c a r r ie d ou t thus f a r , and on th e o ld a v a ila b le g e o lo g ic in f o r
m ation , i t i s concluded th a t th e main l e a d - s i l v e r - z i n c d e p o s it s l i e
w ith in th e S ie r r a de Alamos and S ie r r a la s Plom osas grou p s, and a
p ro sp e c t w ith in th e S ie r r a San Bernardo group. In t h i s p a p er , o n ly th e
m ost prom ising p r o sp e c ts w ith in th e s e groups are d esc r ib e d .
S ie r r a de Alamos Zone. The m ines w hich c o n s t i t u t e t h i s group are
La Q u in tera , Prom ontorio, Santo Domingo, Minas N uevas, San Manuel, and
numerous sm all mine w ork in gs. The m ines are lo c a te d in th e S ie r r a de
Alamos, 10 k ilo m e te r s n o rth w est o f Alamos. T h eir normal a c c e ss from
Minas Nuevas town i s by a d i r t road . Except fo r th e San Manuel M ine, a l l
th e mines l i e in an area 2 .5 k ilo m e te r s w ide by 7 k ilo m e te r s lo n g , which
commences a t Minas Nuevas and f in i s h e s a t Prom ontorio Mine (F igu re 2 ) .
As d e sc r ib e d p r e v io u s ly in Chapter 2 , th e "basement" in th e area
i s r ep re se n ted by g r a n it e , l im e s to n e , and p o r p h y r it ic a n d e s ite on which
th e T e r t ia r y v o lc a n ic rock s were la id down. Based on underground mapping
and o ld a v a ila b le in fo rm a tio n (B rin eg a r , 1910; P ea rce , 1910; P ea rce ,
60
1911a,b; Bloom er, 1909; Sheldom, 1910) a l l th e se ty p es o f rocks are
exposed w ith in th e mine w ork ings.
S tr u c tu r a lly , t h i s group o f mines i s lo c a te d a lon g two w e l l -
d efin ed f i s s u r e z o n e s , which are about 1 .5 k ilo m e te r s ap art and s t r ik e in
a n o r th -e a s t d ir e c t io n . These two f i s s u r e zones are d esc r ib e d by
B rinegar (1910) and Labounsky (1957) as th e e a s t and w est v e in s , which
l i e w ith in th e p o r p h y r it ic a n d e s it e , n ear the g r a n ite -a n d e s it e c o n ta c t
or n ear th e a n d e s ite - lim e s to n e c o n ta c t . In f i e l d r e c o n n a issa n c e , both
v e in s were mapped.
1. E ast V ein: The Prom ontorio, Q u in tera , Santo Domingo, and Minas
Nuevas l i e w ith in th e e a s t v e in , th e "Mother lode" o f th e zone
(Sheldom , 1 910 ). T h is v e in tren d s N 20 -35° E and d ip s 60 -75°
N-W, even though, in th e Zapopan tu n n e l, th e v e in s p l i t s w ith the.
branch s t r ik in g N 10° W and d ip p in g 72° NE (F igu re 17; and
F igure 23 , p . 6 8 ).
T his s t r u c tu r e , which crops ou t ir r e g u la r ly a t th e s u r fa c e ,
has a le n g th o f seven k ilo m e te r s and an average w idth o f e ig h t
m eters (F igu re 1 8 ) .
A b r i e f d e s c r ip t io n o f th e mines w ith in th e e a s t v e in , th e
"Mother lo d e ," i s as fo llo w s :
a . Prom ontorio Mine: The Prom ontorio Mine l i e s a t th e sou th ern
end o f th e v e in . The mine was op erated through a tu n n e l more
than 1 ,000 m eters lon g a t an e le v a t io n o f 560 m eters above
s e a l e v e l . There are th r e e s h a f t s a t 250-m eter in t e r v a ls
which reach depths o f 7 0 , 80 , and 90 m eters from so u th to
61
Figure 17. S p l i t to th e N 10° W o f th e "Mother Lode" S t r u c tu re in the Zapopan Tunnel, Q u in te ra Mine. — View looking N 80° E.
62
n o r th . The mine w orkings below th e tu n n e l are f lo o d e d and no
mapping has been done below t h is l e v e l during th e p r e se n t
in v e s t ig a t io n . Labounsky (1957) r e p o r ts th a t th e r e are th r e e
l e v e l s below th e tu n n el a t 40-m eter in t e r v a l s . Bloomer
(1909) and Sheldom (1910) s t a t e th a t th e d eep est mine working
i s c lo s e to 200 m eters in depth . T h erefo re , i t seems l i k e l y
th a t th e m iners bottom i s p r e s e n t ly about 350 m eters above
s e a l e v e l .
The ore body exposed in th e tu n n e l i s in s to p e p i l l a r s
b ecau se th e m a jo r ity o f th e ore above and below t h i s l e v e l
has been mined o u t. The v e in averages 2 .5 0 m eters in w idth
and a t some p la c e s reach es 5 m eters in w id th . The v e in i s
p r in c ip a l ly in a n d e s ite and in some p la c e s in th e g r a n ite o r
lim esto n e c o n ta c t (F igu re 1 9 ). Based upon th e s to p ed a r e a s ,
th e p a s t p ro d u ctio n o f th e mine i s e s tim a ted a t a h a l f
m il l io n to n s , w ith an average grade o f 30 ounces s i l v e r p er
ton (Labounsky, 1957). Pearce (1911a) r e p o r ts a p a s t produc
t io n o f th r e e -q u a r te r s o f a m il l io n ton s o f v ery h ig h grade
o r e . He s t a t e s (P ea r ce , 1911a, p . 2 0 9 ): " . . . and so r ic h
th a t p r a c t ic a l ly a l l o f i t was packed over 60 m ile s to th e
c o a s t and from th e r e sh ip ped to England fo r trea tm en t."
At th e p r e se n t t im e , th e mine i s in a c t iv e , b u t during th e
coining months some p i l l a r s , which average 700 grams s i l v e r
p er to n , w i l l probab ly be e x tr a c te d .
A|n r i r l r '
n o
W i d t h A s s o y s
P b * / . Z n * Z . A g p p m
1 2 . 6 0 0 . 5 5 4 2 0 1 0 3
2 1 8 5 0 . 9 1 3 8 0 2 8 03 2 0 5 O 8 1 6 2 4 3 4 04 2 6 5 0 7 9 6 6 0 2 5 25 4 8 0 6 5 6 1 4 5 0 2 6 56 3 5 0 4 9 0 9 1 6 6 57 2 6 0 1 0 3 2 9 6 2 9 06 2 2 0 1 2 0 4 1 2 9 6 2 4 5
9 1 7 0 4 8 4 1 5 8 0 1 4 9 0
1 0 1 . 9 0 8 6 4 1 3 9 6 4 6 0
11 5 2 0 4 4 5 7 6 4 3 1 5
1 2 1 . 5 0 1 7 1 4 0 5 4 0
1 3 1 . 7 5 0 9 5 4 . 3 2 9 01 4 2 . 2 5 O 7 3 2 . 1 0 5 0 2
1 6 1 . 6 0 0 3 6 0 3 5 7 2
E S T I M A T E D O R E R E S E R V E S
m e t r i c t o n s *
ProvenP r o b a b l e
Possible
6.000 11000 60 POO
E 3 Tvfff * . • *1 V o l c a n i c o g g l o m e r o t e
P o r p h y r i t i c o n d e s i t e
Q 3 3 G r a n i t e
f - v ! D S k o r n
e s r i s v e i n
— M i n e r a l i z e d I r o c t u r e
B a r r e n I r o c t u r e Geologic c o n t a c t F a u l t
B R a i s e
S h a l t ( H o o d e d )
[ 2 W i n z e ( H o o d e d )
Q C r o s s c u t
i k ' d I n a c c e s s i b l e w o r k i n g s
> = A d . t
S t r i k e a n d d i p
Z C ? S l o p e 2 0 m e t e r s a b o v e
S S a m p l e
A * — ' 8 C r o s s s e c t i o n
G e o l o g y b y A l l r e d o C e r v a n t e s . . 1 6 7 4 .
F ig u re 19. G eologic and Sampling Map o f th e Prom ontorio Mine
64
b . Q u in tera Mine: The Q uin tera Mine i s lo c a te d in th e m iddle
p a r t o f th e "Mother lode" v e in and i t p r a c t ic a l ly a d jo in s th e
• Prom ontorio Mine to th e so u th . T o p o g ra p h ica lly , th e mine
l i e s a t th e h ig h e s t p a r t o f th e v e in , 810 m eters above s e a
l e v e l . T h is mine has been developed by underground e x p lo r a
t io n more than th e o th e r mines in th e d i s t r i c t . At th e su r
fa c e th e r e a re th r e e s h a f t s a long th e v e in , w ith a d is ta n c e
o f 750 m eters . P earce (1 9 1 1 a ), Sheldom (1 9 1 0 ) , and Labounsky
(1957) agree th a t th e r e are 16 le v e l s a lon g th e v e in a t
30-m eter in t e r v a l s , and numerous d r i f t s , r a i s e s and c r o s s
c u ts . The d eep est l e v e l i s 420 m eters below th e su r fa c e a t
an a l t i t u d e o f 360 m eters above s e a l e v e l . In underground
r e c o n n a issa n c e , o n ly th e f i r s t th r e e l e v e l s were mapped due
to th e i n a c c e s s i b i l i t y o f th e low er l e v e l s .
A ccording t o underground mapping c a r r ie d o u t in th e f i r s t
th r e e l e v e l s , th e ore body l i e s e n t ir e ly in th e a n d e s it ic
porphyry in tr u s io n (F igu res 2 0 , 2 1 , 22 , and 2 3 ) . N everth e
l e s s , Sheldom (1910) and Pearce (1911a) rep o rted g r a n ite in
th e s ix t e e n t h l e v e l where th e v e in i s exposed w ith an average
w idth o f 5 m eters , a t some p la c e s a t ta in in g a w idth o f 9 to
15 m eters (B r in e g a r , 1910 ).
The p a s t p ro d u ctio n o f th e Q uin tera Mine i s e s tim a ted a t
1 .5 m il l io n to n s by Labounsky (1957) and a t 2 m il l io n to n s by
P earce (1 9 1 1 a ) . These e s t im a te s are r e a so n a b le , ju d g in g from
mine w orkings and dump s i z e (F igu re 2 4 ) .
4 - '
\
Libcrtad
-r
Libcrtad end Covacha levels,730 meters above sea level
Zapopan level,750 meters above sea level
TIOIcvcl
Inaccessible mine workings
Ore shut
Raise
Shaft
Strike and dip
F ig u re 20 Composite Level P la n t Map o f th e Q u in te ra Mine
66
l - v - 1 Porphyritic andesiteMineralized fracture calcite and iron oxides
- t----Barren fracture.— Vertical fracture
-<• Strike and dip
Vein
g ] Shaft
■ICxT}' Inaccessible raise
y Adit
Inaccesiblc mine workingsr''.. Slope above level
Sample Width A ssaysno meters Pb°/o Zn*/e Ag ppm
1 0 .9 0 0.41 0.45 2702 0 .95 0.12 0.31 1253 1.20 0.17 0.69 2454 0.75 0.25 0.25 1205 1.90 0.4 3 0.51 237
F igure 21. G eo lo g ic and Sam pling Map o f th e Zapopan L ev e l, 750 M etersabove Sea L ev e l, Q uintera Mine.
67
portal 50 m
if v
y v v 1 Porphyritic andesite
Mineralized fracture, ca lc ite , iron oxides Vertical fracture
Vein
Sampleno
Widthmeters Pb
•/.
As s a y s Zn Ag•/. ppm
1 3.20 1.44 2.20 220?. 1.75 1.57 1.75 2553 1.20 1.50 3.31 2254 1.15 6.96 1.33 11005 3.20 0.43 231 1526 2.15 1.10 2.20 4655
"T"" Strike and dip
B Raise
f~ S t o p c above or below level
^ Ore chute
Inaccessible mine workings
A i— i B Cross section
A Adit
m e t e r s
S Sample
F igure 22. G eo lo g ic and Sam pling Map o f th e Covacha L ev e l, 730 M etersabove Sea L e v e l, Q uintera M ine.
68
Forphyritic a n d es i te
1 Estcri le f ra c tu re
M inera l ized f r a c t u r e , calcite and iron oxides
Str ike and dip
Inaccessible mine workings
Shaft
Adit
S Sample
Sample A s s a y s ppm no P b Zn Ag
1440 7 28 49
1680 3680 27
average width of vein 3.20 m e t e r s
m e t e r s
s e c t i o n / 5?
Figure 23. G eo log ic and Sam pling Map o f th e L ib ertad L ev e l, 730 M etersabove Sea L ev e l, Q uintera Mine.
69
Figure 24. Old Dump o f th e Q u in te ra Mine, Alamos D i s t r i c t .
As p r e v io u s ly m entioned , th e Q uin tera Mine i s a c t iv e ;
how ever, th e m ining o p era tio n s are r e s t r i c t e d on ly to th e
dumps, due p r in c ip a l ly to th e la c k o f m ining equipm ent
(F igu re 2 5 ) . From th e dumps, m ineral which co n ta in s an
average grade o f one k ilogram s i l v e r p er ton i s s e le c t e d .
The p ro d u ctio n i s sm a ll and averages o n ly about 5 ton s p er
month.
c . Santo Domingo and Minas Nuevas M ines: These m ines are
lo c a te d two k ilo m e te r s n orth o f th e Q uin tera Mine and l i e
w ith in th e n orth ern exposure o f th e "Mother lode" v e in . Both
m ines are in sh eared zones o f a n d e s i t ic v o lc a n ic rock s
a s s o c ia te d w ith th e p o r p h y r it ic and a n d e s i t ic in t r u s io n . No
d e t a i le d s tu d ie s have been c a r r ie d o u t in th e s e m ines to
d a te . In rec o n n a issa n ce work, on ly some ch ip sam ples from
p i l l a r s were tak en . T h erefo re , th e fo llo w in g b r i e f sk e tch
o f th e s e m ines i s based la r g e ly upon th e o ld a v a ila b le
in fo rm a tio n .
The Santo Domingo Mine l i e s a t an a l t i t u d e o f 550 m eters
above se a l e v e l on th e sou thern s lo p e o f th e Aduana H i l l .
The mine w orkings c o n s is t o f a g lo r y h o le 5 m eters w ide and
40 m eters lo n g . Q uiroga (1953) r e p o r ts th a t a s h a f t rea ch es
a depth o f 115 m eters a t th e fo u r th l e v e l . In th e l e v e l s ,
th e v e in i s exposed w ith a th ic k n e s s o f 3 m eters and an
average grade o f 500 grams s i l v e r p er to n . Sheldom (1910)
70
71
Figure 25. Gambusinos Who Are Working the P o r ta l Covacha Level, 730 Meters above Sea Level, Q u in te ra Mine.
72
s t a t e s th a t th e d e e p e s t l e v e l in the mine reach es 80 m eters
in depth a t an a l t i t u d e o f 470 m eters above se a l e v e l .
No f ig u r e s o f th e p a s t p rod u ction o f th e Santo Domingo
Mine are rep o r te d . However, based upon th e m in e 's dumps, i t
i s ob v iou s th a t t h i s mine has been developed l e s s than th e
o th e r m ines in th e "Mother lode" v e in . Labounsky (1957)
e s t im a te s th a t th e p a s t p rod u ction o f th e mine was o n ly about
5 0 ,0 0 0 ton s w ith a grade o f 500 grams s i l v e r p e r to n .
The Minas Nuevas Mine i s lo c a te d j u s t 200 m eters from th e
Navojoa-Alamos road in th e Minas Nuevas v i l l a g e (F igu re 2 6 ) ,
a t an e le v a t io n o f 490 m eters above s e a l e v e l . The mine
w orkings c o n s is t o f two s h a f t s 300 m eters a p a rt. The f i r s t
a t t a in s o n ly 100 m eters in d ep th , w hereas th e second reach es
200 m eters in depth (Labounsky, 1 9 5 7 ). In th e second s h a f t ,
l e v e l s w ere d riv en a t 10- and 20-m eter in t e r v a ls w ith in th e
main ore body (Y aeger, 1 9 09 ). A lso , th e r e a re numerous
r a i s e s , s t o p e s , and c r o s s -c u ts in th e v e in . P earce (1911a)
e s t im a te s a p a s t p ro d u ctio n o f th e Minas Nuevas Mine to have
been a q u a rter o f a m il l io n to n s o f 600 grams s i l v e r o r e .
West V ein: W ithin th e w est v e in , th e m in es, from n orth to so u th ,
are th e O liv e d e s , Ib a rra , P la ta F in a , Europa, San J o s e , and San
Manuel. T h is s tr u c tu r e tren d s N 2 0 -35° E and d ip s 5 5 -70° SE in
th e n o rth and NW in th e so u th . A ll th e s e m ines are lo c a te d
w ith in a d is ta n c e o f fo u r k ilo m e te r s a lon g th e main s tr u c tu r e
which i s exposed ir r e g u la r ly a t th e su r fa c e and averages two
73
Figure 26. Minas Nuevas Mine (o r Zambona).
74
m eters in w id th . To th e n o r th , th e v e in i s covered by T e r t ia r y
v o lc a n ic r h y o l i t i c f lo w s a t Cerro Cacharamba (F ig u res 6 and 2 7 ) .
A ll th e p r o sp e c ts w ith in th e w est v e in , e x c e p tin g th e San Manuel
M ine, are co m p le te ly in a c c e s s ib le . In a d d it io n , no in form ation
about th e mine w orkings was a v a i la b le . T h ere fo re , th e San Manuel
Mine i s th e o n ly p r o sp e c t which has been mapped in d e t a i l ,
a . San Manuel Mine: The San Manuel Mine i s lo c a te d in a f l a t
a rea , 3 k ilo m e te r s w est o f th e Prom ontorio M ine, a t an
a l t i t u d e o f 350 m eters . On th e b a s is o f a s t r u c tu r a l a l ig n
ment on th e a e r ia l p h otograp hs, i t seems l i k e l y th a t t h i s
mine l i e s in th e sou th ern c o n tin u a tio n o f th e w est v e in .
Furtherm ore, a s im ila r m ineralogy and v e in a t t i t u d e su p p orts
t h i s s u p p o s it io n .
The San Manuel v e in crops ou t a t th e su r fa c e fo r a d i s
ta n ce o f 120 m eters and i s from 1 .2 0 to 2 .0 0 m eters w ide. I t
s t r ik e s N 2 0 -35° E and d ip s 80° NW. There i s a s tro n g b r e c -
c ia t io n and o x id a t io n w ith in th e v e in w hich shows a sharp .
c o n ta c t w ith i t s fo o t w a ll (F ig u res 28 and 2 9 ) . At dep th ,
th e o re body shows a ta b u la r shape and s im ila r s tr u c tu r a l
f e a tu r e s .
T h is mine i s a r e l a t i v e l y new p r o sp e c t which has been
ex p lo red on ly by sh a llo w w ork ings. At th e s u r fa c e , th e r e are
th r e e sm a ll s h a f t s in a d is ta n c e o f 100 m eters . They reach
3 5 , 2 0 , and 25 m eters in depth from n orth to sou th (F igu re
3 0 ) . S h ort d r i f t s ex ten d from 15 to 25 m eters from th e
75
Figure 27. T e r t i a r y R h y o l i t ic Flows o f Cerro Cacharamba.
76
Figure 28. Exposure a t th e Surface o f the San Manuel Vein. — View looking N 25° E.
' i • * I
Figure 29. P ic tu r e Showing B re c c ia t io n and O xida tion W ithin th e San Manuel Vein.
Sampleno
A s s a y s Pb •/« Zn •/. Ag ppm
1 0 . 4 8 1.84 1632 0 .1 1 1.20 783 0 .2 5 0.59 1644 0 .14 0.40 275 0 .41 0.10 536 0 .0 9 0.05 177 0 .3 2 1.15 7008 1 .65 1.57 1589 2.05 0.75 197
10 29.12 15.23 183
a v e r a g e width of ve in 2.10 m e t e r s
mJZZZlEH
B□(&)S
SoilBrccciatod granite Granite VeinGeologic contact Inaccessible mine workings Shaft
• #
PitDumpSample
a r-" '
o Estimated ore re serv esproven 4,000probable 18000possible 50,000
metric tons
- N 30 E
-3 4 0
-3 3 0330+
-3 2 0320+m eters above sea level
m c ters
Figu re 30. G eolog ic and Sampling Map o f th e San Manuel Mine 'vl
s h a f t . A lso , th e r e are e ig h t sh a llo w p i t s a lon g th e v e in
w ith in a d is ta n c e o f 450 m eters.
At th e p r e se n t t im e , th e mine i s b e in g ex p lo red and
e x p lo it e d on a sm all s c a l e . The p ro d u ctio n i s e r r a t ic due to
th e common problem in th e d i s t r i c t : lack o f m ining equipm ent.
I t v a r ie s from 50 to 100 ton s p er month. Based upon mine
w ork in gs, th e p a s t p rod u ction i s e s t im a ted to have been 3 ,0 0 0
to n s a t a grade o f 300 grams s i l v e r and 4% le a d p er to n .
S ie r r a la s Plom osas Zone. The most p rom isin g p r o sp e c ts w ith in
t h i s area are La P lom osas, O ta te s , and Ana Maria m ines. They are lo c a te d
in th e S ie r r a Plom osas some 35 k ilo m e te r s e a s t o f Alamos. The m ines can
be reached by a d i r t road w hich le a d s to th e San Ig n a c io saw m ill in
Chihuahua.
G eom orp h olog ica lly , th e Plom osas and O tates m ines l i e in th e
t r a n s i t io n zone betw een th e B asin and Range and Barranca S e c t io n s o f th e
S ie r r a Madre O c c id en ta l P ro v in ce , where th e Ana Maria M ine, 20 k ilo m e te r s
fa r th e r e a s t , l i e s in th e Barranca S e c t io n (F igu re 3 ) .
The m ines are w h o lly in T e r tia r y v o lc a n ic r o c k s , c h ie f l y o f ande
s i t i c com p o sitio n . In th e v i c i n i t y o f th e ore b o d ie s , th e rock s show a
g e n t le s i l i c i f i c a t i o n , o x id a t io n , and b r e c c ia t io n , and a s tr o n g p r o p y l i t i -
z a t io n . The ore b o d ie s are ep ith erm al v e in s o f l e n t i c u la r and ta b u la r
shape in w hich g a le n a , a r g e n t i t e , and s p h a le r it e are th e main m in e r a ls .
The Plomosas and O ta tes m ines are new p r o sp e c ts in which o n ly
l im ite d underground e x p lo r a t io n has been done. Both p r o sp e c ts have been
in a c t iv e s in c e January 1975 due t o econom ic prob lem s. The Ana Maria Mine
78
79
has been e x p lo ite d and ex p lo red more than th e o th er m ines in th e Plom osas
Zone. Probably th e mine w orkings d ate from th e e a r ly 1 9 0 0 's .
1. Plom osas Mine: The Plom osas Mine i s lo c a te d in th e n o rth s lo p e
o f a sm a ll h i l l a t an e le v a t io n o f 600 m eters above s e a l e v e l .
At th e s u r fa c e , th e Plom osas v e in i s exposed in th r e e ou tcrop s
w ith in a d is ta n c e o f 125 m eters . The o u tcrop s are s m a ll, v a ry in g
from 5 to 10 m eters in le n g th . The v e in s t r ik e s N 2 0 -3 8 ° E and
d ip s 55 to 60° SE, w ith a th ic k n e s s o f .6 0 to 1 .1 0 m eters . Some
150 m eters n o rth o f th e o u tcro p , th e r e are in d ic a t io n s o f
p r o p y l i t i z a t io n , s i l i c i f i c a t i o n , and o x id a t io n , w hich su g g e s t a
c o n tin u a tio n o f th e v e in . Underground, th e v e in shows s im ila r
s t r u c tu r a l f e a tu r e s as a t th e s u r fa c e , b u t th e w idth in c r e a s e s to
1 .7 0 m eters .
The mine had been o p era ted through a tu n n e l 16 m eters below
th e su r fa c e . I t in t e r s e c t s th e Plom osas v e in a t a d is ta n c e o f 20
m eters . From t h i s p o in t , a s o u th e a s te r ly d r i f t in ore rea c h e s a
d is ta n c e o f 82 m eters . There are two r a i s e s in t h i s d r i f t . The
f i r s t i s lo c a te d 30 m eters from th e tu n n e l and co n n ects 19 m eters
above to th e s u r fa c e . An i n c l i n e , 40 m eters from th e tu n n e l,
fo llo w s th e d ip and rea ch es an in c l in e d depth o f 19 m eters
(F igu re 3 1 ) . Three sm a ll d r i f t s have been d r iv en from th e
in c l in e a t d i f f e r e n t d ep th s. H ere, th e v e in v a r ie s from 1 .6 0 to
1 .9 0 m eters in w id th and i s exposed a lon g th e d r i f t s . At th e __
s u r fa c e , th e r e are two in a c c e s s ib le s h a f t s 70 m eters a p a rt.
0 25 50
m e t e r s
Andesite and andesitic aglomerote
Vein
s 11-C
s 13-
s e c t i o ncross
10 20 ___30
m e t e r s
e s t i m a t e d o r e r e s e r v e s m e t r i c t o n s ____________
P r o v e n 1,200 P r o b a b l e 9,500 Possible 20 ,000
Sampleno
A $ Pb •/•
s a y s Zn •/. Ag ppm
i 2.2 1.2 252 5.6 30 1153 1.2 1.1 4 04 2.0 2 6 505 4 4 3.1 bO6 4.5 3 6 607 6.6 7.1 1156 17 9 3.2 3609 1.1 1.5 25
10 6.7 3 5 4011 3 4 3 6 3512 3.3 5 9 2713 0.0 79 12014 1.2 1.5 1 715 5 2 6.5 45
a v e r a g e width of v e in 1.90 m e t e r s
D Shaft (inaccessible)
Raise
Inaccessible mine workings
Adit
Level, 625 m ete rs above sea levelDump, surface 6 4 5 m ete rs above sea level
P ro je c te d mine workings
8 Crosscut
n Portal
------- 'B Cross section
II • ii P ro y e c te d tunnel
s Sample
G eo lo g y by A lf redo C e r v a n t e s , 1974
F ig u r e 31. G eo lo g ic C ro s s -S e c t io n and G eo log ic and Sampling Map o f th e Plomosas Mine00o
A lso , th e r e i s an in a c c e s s ib le tu n n e l 85 m eters e a s t e r ly which
p rob ab ly con n ects w ith th e main tu n n e l.
The mine p ro d u ctio n i s e stim a ted to have been o n ly 5 ,0 0 0
m e tr ic ton s w ith a grade o f 4% le a d , 3% z in c , and 100 grams s i l v e r
p er to n .
2. O ta tes Mine: The O ta tes Mine i s lo c a te d 2 k ilo m e te r s sou th w est
from th e Plom osas Mine. I t l i e s on a f l a t su r fa c e 40 m eters w est
o f a stream bed . At t h i s p o in t , th e v e in crops ou t fo r a len g th
o f 10 m eters and i s from .7 0 to 1 .0 0 m eters in w id th . I t s t r ik e s
N 80° E and d ip s 40 t o 50° SW. There i s ev id en ce a t th e su r fa c e
o f a p o s s ib le c o n tin u a tio n o f th e v e in a lon g 150 m eters n o r th
w e s te r ly from th e o u tcrop .
The mine w orkings c o n s is t o n ly o f an in c l in e d s h a f t w ith in
th e ore body which rea ch es a depth o f 14 m eters and a d r i f t 15
m eters lon g from th e s h a f t bottom (F igu re 3 2 ) . In th e mine
w ork in gs, th e v e in i s exposed w ith an average th ic k n e s s o f 1 .4 0
m eters . A ccording to th e l im ite d underground e x p lo r a t io n , th e
mine p rod u ction has been around 250 ton s a t a grade o f 5% le a d ,
3% z in c , and 100 grams s i l v e r p er to n .
3. Ana Maria Mine: The Ana Maria Mine l i e s 20 k ilo m e te r s e a s t from
th e Plom osas and O ta tes m in es, in a range o f th e Barranca S e c t io n
o f th e S ie r r a Madre O c c id e n ta l, a t an a l t i t u d e o f 1 ,3 0 0 m eters
above se a l e v e l .
At th e m ine, th e ore b o d ie s are hydrotherm al v e in s w ith in
T e r t ia r y a n d e s i t ic r o c k s . The main ore body s t r ik e s N 20 -35° E
81
82
4[ > ^ | Porphyritlc volcanic L----- andesite
rVein
| Projected mineworkings
EH Inclined shaft
AI----1B Section
Dump
S Gamplo
s 3 ----
r
'Si
— s6
/ s9 sl°
s e c t i o n
average width of vein 1.75 metersSample
no PbV.A s s a y
Zn */osAg ppm
1 1.7 2.3 3802 4.8 5.5 703 3.8 6.4 654 3.1 2.4 455 3.3 6.0 GO6 4.1 6.2 1007 3.6 3.8 1308 2.1 2.6 959 4.1 4.7 1 10
10 6.8 4.2 2251 1 4.1 6.5 7512 3.7 4.2 165
He
10-am e t e r s
Geology by
ESTIMATED ORE RESERVESmetric tons
Proven 1,200Probable 6,000Possible 10,000
Alfredo Cervantes., 1974.
F ig u re 32. Sampling Map o f th e O ta te s Mine.
83
and d ip s 70 to 75° NW, w ith an average th ic k n e s s o f 1 .9 0 m e te r s .
There are some s u b s id ia r y v e in s w ith in a sh eared zone some 3
m eters w est from th e main v e in ; th ey s t r ik e in a l l d ir e c t io n s and
vary from .4 0 to 1 .0 0 m eters w id e .
The mine w orkings c o n s is t o f two l e v e l s a t 40-m eter in t e r v a l s
a lon g th e ore body. The f i r s t l e v e l ex ten d s 180 m eters , whereas
th e second i s 350 m eters lo n g . There are some r a i s e s above th e
l e v e l s w hich vary from 10 to 35 m eters in h e ig h t . Most o f th e
o r e , e x c e p t fo r a few sm a ll p i l l a r s , has been removed above th e
f i r s t l e v e l . W ithin th e second l e v e l , a n o r th e a s te r ly d r i f t in
o r e , th e v e in i s exposed fo r a d is ta n c e o f 220 m eters w ith an
average th ic k n e s s o f 1 .9 0 m eters (F igu re 3 3 ) .
At th e p r e se n t t im e , a sm a ll s h a f t i s b e in g sunk a t th e
second l e v e l w ith in th e o re body, e v id e n t ly f o r th e purpose o f
e x p lo r in g th e c o n t in u a t io n o f th e v e in (F ig u res 34 and 3 5 ) .
Based on th e s to p e d a r e a s , i t i s e s t im a te d th a t th e mine has
produced about 5 0 ,0 0 0 to n s a t an average grade o f 5% le a d , 3%
z in c , and 300 grams s i l v e r p e r to n .
S ie r r a San Bernardo Zone. The S ie r r a San Bernardo i s lo c a te d
some 45 k ilo m e te r s n o r th e a s te r ly from Alamos town. I t i s a range in th e
Barranca S e c t io n o f th e S ie r r a Madre O c c id e n ta l. In t h i s S ie r r a l i e s th e
Japon en M exico Mine, w hich i s th e most im portant p r o sp e c t in t h i s area
so f a r . Even though t h i s p r o sp e c t i s o f d i f f i c u l t a c c e s s , i t i s in c lu d ed
in t h i s paper due to th e h ig h v a lu e o f th e ore body.
\
m eters above tea level
O
..."r v . ) i / i
— i r " '
<
,r ? ,1320 ;
v4 & V ‘e.,"-1 o
^ 1 2 ____ r :%
N 3 « E
[ 1 ; | A n d e s i t i c a g g l o m e r a t e
A n d e s i t e
V e i n
F r a c t u r e
____—^ G r a d a t i o n a l c o n t a c t
) -------- A d i t
_____ s e c o n d l e v e l , 1 3 0 7 m e te rsabove s e a l e v e l
F i r s t l e v e l , 1 3 4 7 m e t e r s above s e a l e v e l
" 2 S l o p e a b o v e o r b e l o w l e v e l
r t r : : : I n a c c e s s i b l e m i n e w o r k i n g s
R S h a l t
Q 2 R a i s e d o w n
, 'X , C r o s s c u t
\ ; S l o p e d a r e a
A — S e c t i o n
S S a m p l e
S a m p l e A s s a y sn o P b ♦ / . Z n * / « A g p p m
1 2 . 9 4 1 . 8 7 8 7
2 4 1 2 1 2 6 4 0
3 1 . 1 8 1 8 2 1 6 5
4 2 . 7 9 0 6 3 4 7 1
5 0 9 6 0 . 7 1 2 3 6
6 0 4 8 1 0 0 5 9
7 1 5 7 2 9 8 3 9 0
8 1 4 4 2 3 9 1 2 0
9 4 1 0 3 6 1 2 4 0
1 0 3 6 4 2 3 0 5 81 1 2 5 6 4 2 8 6 5
1 2 3 6 9 2 9 4 2 1 51 3 8 4 8 2 8 0 1 6 61 4 6 6 1 2 5 0 2 1 61 5 0 1 1 0 4 2 5 31 6 0 4 3 0 1 8 1 4 0
1 7 0 3 7 4 2 7 2 3 8
1 8 0 6 1 0 4 7 1 8 01 9 0 4 2 0 4 2 1 9 0
2 0 2 2 7 1 2 5 4 7 5
a v e r a g e w i d t h v e i n I S O m e t e r s
F ig u re 33. G eolog ic and Sampling Map o f th e Ana M aria Mine, F i r s t and Second Levels 00A
F igu re 34. Gambusinos Who Are Working th e Ana M aria Mine, P o r ta l o f Second Level, 1,307 M eters above Sea Level.
F igure 35. D ir t Roads Which Communicate to th e Ana M aria Mine in th e Alamos D i s t r i c t .
86
1. Japon en Mexico Mine: The mine i s lo c a te d 20 k ilo m e te r s e a s t o f
th e San Bernardo v i l l a g e , a t an a l t i t u d e o f 1 ,1 5 0 m eters . The
a c c e ss to th e mine i s by a d i r t road as fa r as th e F r i j o l v i l l a g e ;
from t h i s p o in t , th e jou rn ey i s 12 hours by h orse becau se th e r e
are no roads to th e m ine.
The Japon en M exico p ro sp e c t l i e s in th e p o r p h y r it ic v o lc a n ic
a n d e s ite in c o n ta c t w ith lim esto n e ; how ever, no in d ic a t io n o f
m etasom atism i s p r e s e n t . The ore body i s a t th e a n d e s it e -
lim esto n e c o n ta c t , which shows an E-W s t r ik e and a d ip o f 85° N;
th e average th ic k n e s s i s 1 .0 0 m eter. At th e s u r fa c e , th e r e i s
ev id en ce o f a p o s s ib le c o n tin u a tio n o f th e v e in some 80 m eters
e a s t o f th e main o u tcrop . In th e v e in , th e main m in era ls are
s p h a le r i t e , a r g e n t i t e , g a le n a , and ir o n o x id e s . The gangue
m in eral i s q u artz and ch a lced on y .
The mine w orkings c o n s is t o f 3 l e v e l s a t 8 -m eter in t e r v a l s .
Along th e l e v e l s , th e r e are 3 d r i f t s in ore which reach 10 , 20 ,
and 30 m eters in le n g th (F igure 3 6 ) .
Based on th e s to p ed a r e a s , th e p a s t p ro d u ctio n i s e s t im a te d
a t 600 to n s w ith an average grade o f 1 k ilogram s i l v e r , 15% z in c ,
2% le a d , and 8 grams g o ld p e r to n .
A c tu a lly , th e mine i s a c t iv e , but th e p ro d u ctio n i s n o t
c o n s is t e n t due to th e d i f f i c u l t y o f sh ip p in g th e o re and th e la ck
o f m ining equipm ent.
I t i s p o in te d ou t th a t th e p r o sp e c ts La R eina, w ith in th e S ie r r a
de B avisp e zone; La V io le ta , w ith in S ie r r a d e l Chapote zone; and P ied ra s
87
meters chovc sea level11201-
1110 ' -1110
11001
" / /
Sampleno Pb •/•
A ssa y s Z n •/• Ag ppm Au ppm
1 1.51 14.25 584 3.82 1.35 15.04 1 0 0 6 15.33 1.34 23.36 1 0 6 0 46.34 1.57 15.52 1 1 20 10.25 1.97 24 .80 4 80 5.5G 1 .51 14.23 9 7 6 8.4
Estimated ore reservesmetric tons
Proven 1.500Probable 5.000Possible 1 0 0 0 0
K d Porphyritic vofeanic ---- andesiteg g ] Skorn
s = t Vein Geologic contact
•’ Projected mine Cl'ff workings
A PortalB Shaft ( inaccessible)
ai— ib Section
S Sample
0 5 10 20
m eters
F ig u re 36 Com posite P lan M ine. View and C ro s s -S e c tio n o f th e Japon en Mexico
88
V erdes, w ith in Lomas de Los Tanques zone; show a ls o good p o s s i b i l i t i e s
fo r f in d in g o r e . C onseq u en tly , th e se p r o sp e c ts and some more cou ld g iv e
a d d it io n a l o re r e se r v e s fo r th e d i s t r i c t . N e v e r th e le s s , th e s e p r o sp ec ts
have n o t been s tu d ie d in d e t a i l so f a r .
Economic A sp ects
Grade o f Ore
On th e b a s is o f th e p re lim in a ry and d e t a i le d sam pling c a r r ie d ou t
in th e n in e p ro sp e c ts p r e v io u s ly d escr ib ed and upon th e l a s t m in era l
q u o ta tio n o f th e June r e p o r t o f th e E .M .J. (1 9 7 5 ). The average grade and
v a lu e o f th e n in e p ro sp e c ts are c a lc u la te d as fo llo w s :
S i lv e r 400 grams p er ton
Gold 0 .6 5 grams p er ton
Lead 2.88%
Zinc 3.38%
Copper 0.67%
Average v a lu e o f ore in p la c e eq u a ls $116 .80 p er m e tr ic ton
(Appendix A shows th e c a lc u la t io n s in d e t a i l ) .
I t i s em phasized th a t th e c a lc u la te d ore grade i s from s u l f id e s
in th e o x id iz e d zone some 25 to 50 m eters above th e w ater t a b le , b ecau se
no sam pling has been c a r r ie d ou t below t h i s l e v e l due to i n a c c e s s i b i l i t y
o f mines o r sh a llo w mine w ork in gs.
N e v e r th e le s s , im portant in fo rm a tio n about th e o re grade below th e
w ater ta b le i s g iv e n by th e p rev io u s w orkers who v i s i t e d th e m ines when
th ey were o p e r a t in g . Among them, B rin egar (1910 , p . 554) s t a t e s :
"The o re from th e mines in th e w est c o n ta c t . . . a ssa y v a lu e s range from
15 to 5 ,0 0 0 o z . s i l v e r and up to $70 .00 in g o ld ." Labounsky (1 9 5 7 , p . 16)
em phasizes: "From th e r e p o r t o f S u p erin ten d en t C. Mahaut, December,
1908, th e Q uin tera Mine low er w orkings (1 3 , 14, 15, and 16 le v e l s ) showed
ore in p la c e a t an average o f 36 ounces o f s i l v e r p er to n ." A lso ,
Sheldom (1 9 1 0 , p . 920) m en tion s, in r e s p e c t to th e 1 ,500 f e e t l e v e l o f
th e Q uin tera Mine: "The v e in a t d ep th , fo r 20 to 30 f e e t in w id th ,
would a ssa y 40 to 50 o z . in s i l v e r . Lead gave ou t and copper came in th e
amount o f 8 to 9%." C oncerning th e Minas Nuevas m ine, th e r e are rep o r ts
by P earce (1911b , p . 682): "The v e in has been cut by a tu n n e l a t a
depth o f about 450 f e e t where a t e tr a h e d r i t e o re ca rry in g up t o 3 ,0 0 0 o z .
o f s i l v e r p er ton has been encountered"; and Sheldom (1 9 1 0 , p . 9 2 0 ):
"The v e in i s 20 to 30 f e e t w ide and co n ta in s an average o f 24 o z . s i l v e r
w ith some le a d ."
I t ap p ears, accord in g to th e c i t e d a u th o rs, th a t th e ore sam pled
from th e s to p e s and p i l l a r s was l e f t in i t s p la c e b ecau se a t th a t tim e
such v a lu e s w ere u neconom ica l. T h erefo re , i t seems l i k e l y t h a t , i f th e
low er mine w orkings were sam pled, h ig h e r o re v a lu e s cou ld be o b ta in e d .
Ore R eserves
A p r e lim in a r y e s t im a te o f o re r e s e r v e s , a t th e n in e d esc r ib e d ore
b o d ies in th e Alamos Mining D i s t r i c t , i s b ased upon th e l im it e d mine
w ork in gs, underground mapping and g e o lo g ic f a v o r a b i l i t y . A ccording to
th e o re d e p o s it s ' c h a r a c t e r i s t i c s , th e ore i s c l a s s i f i e d as proven ,
p ro b a b le , and p o s s ib le r e s e r v e s .
89
Based upon s tu d ie s o f 70 ep itherm al d i s t r i c t s and 40 y ears o f
ex p er ien ce w ith in th e P reciou s M etal P rovince o f n orth w estern M exico,
where th e Alamos M ining D i s t r i c t l i e s , W isser (1966) determ ined th a t th e
average v e r t i c a l range o f ore was 300 m eters a t th e tim e o f ore d e p o s i
t io n . T h erefo re , in ord er to e s t im a te th e p rob ab le and p o s s ib le r e se r v e s
in th e m ines' d i s t r i c t , such rea so n in g i s taken in to a cco u n t. Appendix A
shows th e e s tim a te d r e se r v e s o f each m ine.
Proven R e se r v e s . The e s t im a tio n o f proven r e se r v e s in t h is rep o rt
in c lu d e s th e o re p r e se n t in th e e x p lo r a tio n mine w orkings such as d r i f t s ,
tu n n e ls , a d i t s , e t c . They are c a lc u la te d accord in g to th e d im ensions and
d e n s ity where th e o re b o d ie s are exp osed . They are e s tim a ted a t 32 ,000
m etr ic to n s .
Probable R e se r v e s . T his ca teg o r y o f r e se r v e s i s c a lc u la te d
ta k in g in to account th e measurement o f sto p ed areas in th e m a jo r ity o f
th e m ines and assum ing th e p e r s i s t e n t tren d o f ore b o d ie s in d ep th .
These r e se r v e s are e s tim a ted o n ly by c o n s id e r in g 25 m eters below th e
p r e se n t mine w ork in gs, which appears a rea so n a b le e s t im a tio n acco rd in g
t o W isser 's con cep t fo r t h i s typ e o f d e p o s it . They are e s tim a te d a t
181 ,000 m e tr ic t o n s .
P o s s ib le R e se r v e s . These r e s e r v e s are in fe r r e d based upon th e
fa v o r a b le s t r u c tu r a l fe a tu r e s which in d ic a te a p rob ab le c o n t in u ity in
le n g th and depth o f th e o re b o d ie s n o t o n ly in th e S ie r r a de Alamos m ines
but a ls o in th e S ie r r a Plomosas m in es. The r e se r v e s are c a lc u la te d by
in c r e a s in g th e depth 25 m eters from th e l e v e l o f p rob ab le r e s e r v e s . A
very c o n se r v a t iv e c a lc u la t io n o f th e s e r e se r v e s i s 490 ,0 0 0 m e tr ic to n s .
90
91
M oreover, in a d d it io n to th e ore r e se r v e s c a lc u la te d above, th e r e
i s an area o f " p o te n t ia l o re r e se r v e s" among th e Prom ontorio , Q u in tera ,
Santo Domingo, and Minas Nuevas m in es, which i s e s t im a te d a t a minimum
o f 1 ,0 0 0 ,0 0 0 m e tr ic to n s (F ig u re 3 7 ) .
E xp lora tion Program
A fte r a n a ly z in g th e r e s u l t s o f the rec o n n a issa n ce and d e t a i le d
su rveys in th e Alamos M ining D i s t r i c t , i t i s s tr o n g ly recommended th a t
t h is work be fo llo w ed up w ith an in te n s iv e e x p lo r a tio n program.
The main purpose o f th e e x p lo r a tio n program i s tw o - fo ld . F i r s t ,
to ev a lu a te and to confirm th e p o s s ib le ore e x te n s io n in depth below th e
p r e se n t w orkings underground in th e m ines a lrea d y d e sc r ib e d . Second , to
ex p lo re th e area among th e o ld m ines in th e S ie r r a de Alamos, w ith th e
goa l o f sea rch in g fo r new ore b o d ie s , p r in c ip a l ly w ith in th e "Mother lode"
s t r u c t u r e .
The f i r s t phase o f th e program c a l l s fo r core d r i l l i n g from th e
su r fa c e and underground as w e ll as underground ex p lo r a to r y w ork in g s. I t
i s e stim a ted t h a t , in th e o ld m in es, th e low er l e v e l s w i l l have to b e
dew atered and the tim b erin g would need some r e p a ir . I t i s c a lc u la te d
th a t t h is phase o f th e program cou ld be c a r r ie d o u t by c o n tr a c to r s in a
p er io d o f tw e lv e months a t a c o s t o f approxim ately $ 3 5 0 ,0 0 0 .0 0 . An e s t i
m ation o f th e d ir e c t c o s t and tim e f o r each mine i s e x p la in e d in
Appendix A.
i The second phase o f th e e x p lo r a tio n program, which may be c a r r ie d
out s im u lta n e o u s ly w ith th e d r i l l i n g program, would be geochem ical and
g eo p h y sica l su r v e y s . Both s tu d ie s fo cu sed to d e te c t new ore b o d ie s
m ete rs above sea level
m e te rs above sea level
800
600
400
200A B C E x p lo re t i o n a re a s for o re
E st im a ted p o te n t ia l ore r e s e r v e s 1,000,000 metric tons
- 8 0 0
- • 600
.. 400
-•200
0 1 2
k i l o m e te r s her. scale
F igu re 37 Schem atic C r o ss-S e c tio n o f th e Mines W ithin th e "Mother Lode" V ein Showing Areas fo r Ore E x p lo ra tio n . UD
ts>
93
w ith in th e "Mother lode" s tr u c tu r e . The geochem ical program would in c lu d e
s o i l and ch ip sam ples p e rp en d icu la r to th e tren d o f the main s t r u c tu r e s .
The g eo p h y s ica l program would in c lu d e a Turam su rvey a ls o p erp en d icu la r
to th e main tren d o f v e in s . I t must b e m entioned th a t a rec o n n a issa n ce
e le c tr o m a g n e tic su rvey in t h i s area was conducted by V elasco (1 9 6 2 ) .
From t h is s tu d y , he was a b le to d e te c t some in d ic a t io n s o f v e in in dep th .
T h erefore , i t seems l i k e l y th a t such stud y would g iv e good r e s u l t s . I t
i s e s t im a ted th a t both su rv ey s cou ld be c a r r ie d ou t in 4 months by p e r
son n el o f th e C .R .N .N .R. a t an in d ir e c t c o s t o f some $ 3 0 ,0 0 0 .0 0 .
I f th e p o s s ib le p resen ce o f a new o r e body i s d e te c te d by th e se
m ethods, some a d d it io n a l d r i l l i n g would be n e c e s sa r y .
Economic C o n sid era tio n s
I t can be em phasized th a t th e fo llo w in g econom ic c o n s id e r a t io n s
are based on the assum ption th a t a t l e a s t 70% (5 0 0 ,0 0 0 m e tr ic to n s) o f
th e e s tim a ted ore r e se r v e s w i l l b e found. There a r e , o f c o u r se ,
p o s s i b i l i t i e s fo r p r o f i t a b le o p era tio n a t o th er l e v e l s o f p ro d u ctio n and
w ith o th er e stim a ted ore r e s e r v e s .
The p re lim in a ry e v a lu a t io n o f th e n in e m ines d e sc r ib e d in th e
Alamos D i s t r i c t in c lu d e m ining and p r o c e s s in g c o s t s , n e t sm e lte r r e tu r n ,
c a p ita l req u irem en ts, r a te o f m ining and mine l i f e , p r o f i t a b i l i t y
a n a ly s is , and s e n s i t i v i t y a n a ly s is .
M ining and P r o c e ss in g C o s ts .
1 . M ining: Taking in t o account th e sh ape, s i z e and a t t i t u d e o f th e
o re b o d ie s w ith in th e d i f f e r e n t m ines in th e d i s t r i c t , a s u i t a b le
m ining system fo r e x tr a c t in g th e m inera l from th e d e p o s it appears
94
to be sh rin k age s lo p in g combined w ith cu t and f i l l s lo p in g o r
s u b - le v e l s lo p in g . By u t i l i z i n g th e s e m ining m ethods, a reco v ery
o f 90% from th e v e in s i s e s t im a te d .
The m ining c o s t s are c a lc u la te d by comparing th e a t t i t u d e o f
th e o re b o d ie s in th e d i s t r i c t w ith tw enty s im ila r m ining
o p e r a tio n s (C. M. M ., 1972; Cummings and G iven , 1 9 7 3 ). The c o s t
o f m ining i s e stim a ted a t $15 .00 p er m e tr ic to n , which in c lu d e s
e x p lo r a t io n , developm ent, s lo p e p r e p a r a tio n , v e n t i l a t io n , h a u lin g ,
h o is t in g , and o th e r underground a c t i v i t i e s .
2 . P ro c ess in g : A ccording to econom ic c o n s id e r a t io n s , in c lu d ed in
t h i s p ap er, i t i s determ ined th a t th e ore from th e m ines sh ou ld
be tr e a te d a t th e v i c i n i t y o f th e m ines and th a t th e co n c e n tr a te s
cou ld be s e n t to th e sm e lte r s a t Chihuahua and Torreon fo r
sm e lt in g .
A m il l s i t e co n v en ien t fo r t a i l i n g d is p o sa l cou ld be s e le c t e d
a t th e v i c i n i t y o f th e Aduana town. In t h i s lo c a t io n , th ere are
o ld b u ild in g s which cou ld be rep a ired fo r th e o p e r a tin g p erson n el
and u t i l i t i e s .
A m i l l o p e r a tin g a t a r a te o f 200 m e tr ic to n s p er day would
c o n s is t o f r e c e iv in g b in , co a rse c r u sh e r s , b a l l m i l l s , f l o t a t io n
c e l l s , and a l l th e equipm ent fo r p r o c e s s in g .
Taking in t o account th a t the ore from th e v e in s i s c o a r se
g r a in e d , i t i s e s t im a te d th a t an average r a t io o f c o n c e n tr a tio n
would b e 1:20 fo r l e a d - s i l v e r and z in c co n c e n tr a te s fo r th e
m ineral from a l l the m in es .
95
The o p e r a tin g c o s t s , in c lu d in g la b o r , s u p p l i e s , e l e c t r i c i t y ,
n a tu ra l g a s , w a ter , and m ain tenance, are c a lc u la te d a t $10 .00 p er
m e tr ic ton o f o r e . T h ere fo r e , th e t o t a l c o s t o f o p e r a t io n , w ith
a 20% as a s e c u r it y f a c t o r , i s e s t im a te d a t a maximum o f $3 0 .0 0
p er m e tr ic to n o f crude o re mined. Appendix A e x p la in s th e c o s t
in d e t a i l .
Net S m elter R eturn . A ccording t o m i l l in g t e s t s and payment
s h e e ts fo r th e o re from th e Q u in tera , San Manuel, O ta te s , and Plomosas
mines a t th e La Reforma p la n t , th e average m i l l in g reco v ery i s as
fo llo w s :
S i lv e r 85%
Gold 85%
Lead 83%
Zinc 80%
T h erefo re , ta k in g in to account th a t the m in e r a lo g ic a l fe a tu r e s o f
th e Prom ontorio, Santo Domingo, Ana M aria, and Japon en M exico m ines are
analogous to th e m ines in which m i l l in g t e s t s have been done, a s im ila r
m il l in g reco v ery i s assumed fo r th e s e m ines.
The average grade o f o re from a l l th e m in es, in c lu d in g 10% o f
d i lu t io n i s c a lc u la te d a s:
S i lv e r 366 grams p er ton
Gold 0 .6 grams p er ton
Lead 2.6%
Zinc 3.0%
Average r a t io o f c o n c e n tr a tio n i s 1 :20 .
A ccording to th e l a s t E.M .J. m inera l q u o ta tio n , fo r June 1975,
and b ased upon the. sch ed u le o f La Reforma (1975) p la n t , which i s v ery
s im ila r to th e sch e d u le s o f th e Chihuahua and Torreon p la n t s , th e n e t
sm e lter re tu rn i s c a lc u la te d as:
96
R atioC on cen tration Net
Net sm e lte r re tu rn on Pb-Au-Au co n c e n tr a tio n $ 1 ,0 0 0 .0 0 1:20 $50.00
Net sm e lte r re tu rn on Zn co n c e n tr a tio n $ 170 .00 1:20 $ 8 .5 0
T ota l re tu rn p er m e tr ic ton mined $58 .50
Appendix A e x p la in s th e c a lc u la t io n in d e t a i l .
R atio o f M ining and Mine L if e . As a lrea d y m entioned , i f during
th e proposed e x p lo r a tio n program 70% o f th e e s tim a ted p rob ab le and
p o s s ib le ore r e se r v e s cou ld be proven , th a t i s , 500 ,000 m e tr ic to n s , th e
r a te o f m ining i s c a lc u la te d a t 200 m e tr ic to n s /d a y . Thus, th e produc
t io n p er y ea r on a 300 la b o r days b a s is cou ld be 6 0 ,000 to n s . C onse
q u e n tly , th e l i f e o f m ining o p e r a tio n s i s e s t im a ted as a t l e a s t 8 y ea rs
o f p ro d u ctio n .
The p rep rod u ction p e r io d , ta k in g in to account th e m ines' co n d i
t io n , i s e s t im a te d as a t l e a s t 2 y ea rs a f t e r commencing th e e x p lo r a tio n
work.
C a p ita l R equirem ents. The e s t im a tio n o f th e t o t a l c a p it a l in v e s t
m ent, fo r d ev e lo p in g th e m ines a lrea d y d e sc r ib e d , in th e Alamos M ining
D i s t r i c t , i s determ ined b ased upon s im ila r o p e r a tin g p la n ts (Cummings and
G iven, 1973; C.M.M., 1 9 7 2 ) . The t o t a l c a p it a l in vestm en t fo r t h i s
m ining v en tu re i s e s t im a te d a t:
97
C a p ita l c o s t o f p r o c e s s in g p la n t $ 8 5 0 ,0 0 0 .0 0
Underground equipment and developm ent $ 4 5 0 ,0 0 0 .0 0
Mine p rep rod u ction c o s t (e x p lo r a t io n ) $ 3 5 0 ,0 0 0 .0 0
Working c a p ita l $ 100, 000.00
S u b -to ta l $ 1 ,7 5 0 ,0 0 0 .0 0
Overhead (15%) • $ 2 5 0 ,0 0 0 .0 0
T ota l c a p it a l in v estm en t (U .S . D o lla r s ) $ 2 ,0 0 0 ,0 0 0 .0 0
Or $ 1 0 ,0 0 0 .0 0 p er ton day c a p a c ity
P r o f i t a b i l i t y A n a ly s is . The e s t im a te o f p r o f i t a b i l i t y i s c a l
c u la te d accord in g to th e m ining law o f M exico (L e g is la c io n M inera, 1956)
and accord in g to fe d e r a l laws o f ta x e s o f M exico (Ley F ederal de Im puesto,
1 9 6 6 ). However, such c a lc u la t io n s are o n ly a p re lim in a ry f ig u r e due to
some changes as a r e s u l t o f th e n a t io n a l iz a t io n o f th e m ining in d u str y
as w e ll as due to th e p o s s ib le agreem ents w ith th e owners o f th e mine
p r o p e r t ie s , w hich are n o t in th e sco p e o f t h i s s tu d y .
N e v e r th e le s s , i t i s hoped th a t th e econom ic a n a ly se s m ight g iv e
an id e a con cern in g th e p r o f i t a b i l i t y o f a p o s s ib le in vestm en t in th e
Alamos M ining D i s t r i c t .
The v a r io u s econom ic e v a lu a t io n tech n iq u es in c lu d ed in t h i s paper
are n e t p r e se n t v a lu e , d isco u n ted cash f lo w , payback p e r io d , a cco u n tin g
r a te o f re tu rn and p r e se n t v a lu e r a t io . They are c a lc u la te d accord in g
to Rudawsky (1970) and are b ased upon th e e s tim a ted c a p it a l in v estm en t,
o re r e s e r v e s , p rod u ction r a t e , mine l i f e , g ro ss rev en u e , and p rod u ction
c o s t s . A summary o f th e r e s u l t s o b ta in ed from th e c a lc u la t io n s i s
(Appendix A e x p la in s th e c a lc u la t io n s in d e t a i l ) :
N et p r e se n t v a lu e @ 25% d isc o u n t r a t io
D iscou n ted cash flow re tu rn on in vestm en t
Payback p er io d
P resen t v a lu e r a t io @ 25%
A ccounting r a te o f re tu rn
$ 5 5 2 ,4 0 0 .0 0
36.67%
3 .2 y ea rs
0 .4 4 5
98
30.40%
T h erefo re , b ased upon th e r e s u l t s o b ta in ed , i t i s ob v iou s th a t
m ining in th e d i s t r i c t would be a p r o f i t a b le p r o je c t fo r in vestm en t i f
th e e s tim a ted r e se r v e s are proven during th e e x p lo r a tio n program.
S e n s i t iv i t y A n a ly s is . The fo llo w in g a n a ly s is i s b ased upon th e
assum ption o f a group o f fa v o r a b le c o n d it io n s a c t in g to g e th e r in th e
d i s t r i c t . There are many o th e r com binations and c o n d it io n s th a t would be
fa v o ra b le b u t th ey are n o t in c lu d ed in t h i s p a r t ic u la r a n a ly s is .
For an id e a about th e in v e s tm e n t's s e n s i t i v i t y b ecau se o f
p o s s ib le changes in m etal p r ic e an d /o r p rod u ction c o s t s , an u n favorab le
change o f 20% i s assumed in th e e ig h t y ears o f mine l i f e . From t h i s , th e
r e s u l t s o b ta in ed are (A ppendix A in c lu d e s th e c a lc u la t io n s in d e t a i l ) :
Net p r e se n t v a lu e @ 25% d isc o u n t r a t io $ 7 3 ,7 2 2 .0 0
D iscou n ted cash flow re tu rn on in v estm en t 26.20%
Change in th e p r o f i t a b i l i t y 26.80%
C onseq u en tly , i t i s b e l ie v e d th a t th e s e changes would n ot have a
s tr o n g e f f e c t on th e in v estm en t. In a d d it io n , th e payback p e r io d , e s t i
mated on 3 .2 y e a r s , cou ld a ls o be a p p lic a b le fo r m easuring th e r i s k .
CHAPTER 4
STATISTICAL ASPECTS
In tr o d u ctio n
. when you can measure what you are sp ea k in g about and exp ress i t in numbers, you know som eth ing about i t ; b u t when you cannot ex p ress i t in numbers, your knowledge i s o f a meagre and u n s a t is fa c to r y k ind; i t may be th e b eg in n in g o f know ledge, b u t you have s c a r c e ly in your th ou ghts advanced to th e s t a t e o f s c ie n c e , w hatever th e m atter may b e ."
Lord K elvin(Taken from D a v is , 1973, p . 1)
T h is ch ap ter c o n s id e r s some g e o s t a t i s t i c a l a sp e c ts to p ro v id e
q u a n t ita t iv e e s t im a te s o f th e e x p lo r a tio n p o t e n t ia l o f th e Alamos M ining
D is t r ic t from th e a p p lic a t io n o f s t a t i s t i c a l tech n iq u es t o th e a n a ly s is
o f s y s te m a t ic a l ly mapped g e o lo g ic a l in fo rm a tio n .
Q u a n tif ic a t io n o f g e o lo g ic a l fe a tu r e s and th e subsequent u se o f
m athem atics, e s p e c ia l ly s t a t i s t i c s , t o t r e a t num erical d a ta fo r c l a s s i f i
c a t io n , c o r r e la t io n , and e x tr a p o la t io n are now w id e ly a p p lie d in v a r io u s
branches o f g e o lo g y . Even though th e b a s ic fo u n d a tio n s fo r th e framework
o f th e a p p lic a t io n w ere la id e a r l i e r , la r g e - s c a le p r o c e s s in g o f d ata
became p o s s ib le w ith th e advent o f th e com puter. Computer tech n iq u es in
th e v a r io u s f i e l d s o f g eo lo g y have been g iv en by W eiss (1 9 6 9 ) , Koch and
Link (1 9 7 1 ) , and a r e c e n t book by D avis (1 9 7 3 ) .
Among th e s c i e n t i s t s who have d eveloped th e s t a t i s t i c a l methods
are A l la i s (1 9 5 7 ) , H a rr is (1 9 6 5 , 1968, 1 9 7 3 ) , De G eoffroy and W idnall
99
(1 9 7 0 ) , Krumbein and G r a y b ill (1965) , S in c la i r and Woodsworth (1 9 7 0 ) ,
Koch and Link (1971) , A gterberg and o th ers (1972) , and D avis (1973) .
A l la i s (1957) was one o f th e p io n eer s in d ev e lo p in g the s t a t i s
t i c a l methods to e x p lo r a t io n . N e v e r th e le s s , he gave no c o n s id e r a t io n to
th e g e o lo g ic fe a tu r e s in th e area ex p lo red . T h ere fo r e , h i s r e s u l t s were
based o n ly on m athem atical p rem ises .
The f i r s t s i g n i f i c a n t advances o f m athem atical rea so n in g to
e x p lo r a tio n , ta k in g in to account th e r e g io n a l g eo lo g y o f th e areas under
s tu d y , was made by H arris (1 965 , 1 9 6 8 ). C on seq u en tly , he was a b le to
p r e d ic t the m etal endowment o f v a r io u s areas accord in g to i t s s i z e and
g eo lo g y .
A gterb erg and o th e r s (1972) and th e U. S . G e o lo g ica l Survey
(1 9 7 2 ) , b ased e s s e n t i a l l y upon H a r r is ’ m odel, c a r r ie d out s im ila r s tu d ie s
to y i e l d t e n t a t iv e e s t im a te s o f u n d isco v ered r e s o u r c e s .
Model and M ethodology Employed
In t h i s p ap er, th e H arris m odel, w ith some m o d if ic a t io n s , i s
taken as a b a s is f o r e s t im a tin g th e e x p lo r a tio n m inera l p o t e n t ia l o f th e
Alamos M ining D i s t r i c t .
Fundam entally , th e m ethodology and b a s is o f th e H arris model are
as fo llo w s :
1 . The r e g io n o f stu d y i s su b d iv id ed in to an a r b itr a r y number o f
c e l l s e q u a lly spaced ( g r i d ) , based upon th e mapped a v a ila b le
g e o lo g ic in fo r m a tio n , to q u a n tify a number o f g e o lo g ic a l
v a r ia b le s w ith in each c e l l .
100
101
2 . An area i s tak en as a ”c o n tr o l area" fo r e s t im a t in g th e m ineral
p o t e n t ia l o f th e w hole area under s tu d y .
3. The " le v e l" o f g e o lo g ic in fo rm a tio n , such as r e g io n a l , sem i-
d e t a i le d o r d e t a i l e d , i s o f v i t a l im portance b ecau se from th e s e
g e o lo g ic d ata th e l e v e l o f r e l i a b i l i t y o f th e e s tim a ted m ineral
reso u rce s in th e area are d e r iv e d .
4 . The m athem atical tech n iq u e employed in ord er to e s t im a te th e
g e o lo g ic v a r ia b le s w ith in th e area i s m u lt iv a r ia te g e o s t a t i s t i c a l
a n a ly s i s . '
A b r i e f ex p la n a tio n o f th e procedure employed w ith th e g e o lo g ic a l
data w ith in th e Alamos D i s t r i c t i s as fo llo w s :
1. Based upon th e g e o lo g ic map o f th e d i s t r i c t (F ig u r e 6 ) , th e area
was su b d iv id ed in to 140 c e l l s o f 2 .5 x 2 .5 k ilo m e te r s (F igu re 3 8 ) .
2 . No c e l l was taken as " co n tro l area" due to th e low l e v e l o f
g e o lo g ic in fo rm a tio n (rec o n n a issa n ce l e v e l ) .
3 . The measured g e o lo g ic fe a tu r e s were t r e a te d as dummy v a r ia b le s o r
p rese n c e /a b se n c e w ith in each c e l l . The dependent v a r ia b le chosen
was th e number o f mines p er c e l l , and th e independent v a r ia b le s
w ere th e g e o lo g ic fe a tu r e s l i s t e d in T able 2 .
4 . The m athem atical tech n iq u e used in ord er to e v a lu a te th e ex p ected
number o f mines p er c e l l was m u lt ip le s te p w ise r e g r e s s io n
a n a ly s i s . The computer program employed was th e S t a t i s t i c a l
Package fo r th e S o c ia l S c ie n c e s (1 9 7 5 ) , w ith a CDC 6400 computer
a t th e Computer C enter o f The U n iv e r s ity o f A rizon a .
109° 10" 109*00"__ ____________ i. 1 2 3 4 ■ &&
Mocuzoh6 7 8
i9 10
11 12 13 ' 14 15 16 17 18 19 20
.21 22 23 24 25 26 27 4&28PiedrasVerdes
29 30
31 32 33 34 35 36 37 38 39 40
41 42 4 3 4 4 45 46 47 4 8 4 9 s o
51 52 53 54 5 5 56 • 57 58
MinasNuevas
5 9 60
61 62 63 64 65 • 66 67 * 68 69 70
71 72Dolisa
73 74 75 76 77 78 79 VS3 0Alamos
81 82 83 84 0 5 86 87 8 8 8 9 SO -
91 92 93 94 9 5 96 97 98 9 9 100
101 102 103 104 105 106Oastras
107 108 109 - 110
111 112 113 114 115 116 117 118 119 120
121 122 123 124 125 126 127 128 129 130
131 . 132 133 134 135 136 . 137 138 139 140
0____________ 5 10
kilometers
F igu re 38 . G rid o f C e l l s f o r th e Alamos D i s t r i c t
103
Table 2 . G e o lo g ic a l V a r ia b le s Coded fo r th e Alamos Mining D i s t r i c t .
Measured V a ria b les
Dependent v a r ia b le : number o f m ines p er c e l l
Independent v a r ia b le s : rock typ e
1 . g r a n ite
2 . p o r p h y r it ic a n d e s ite (Laramide)
3 . v o lc a n ic rock s (T e r tia r y )
4 . metamorphic rocks
fr a c tu r in g
5 . NE fr a c tu r e s
6 . NW fr a c tu r e s
7 . EW fr a c tu r e s
rock age
8. age o f rock
co o rd in a te s
9 . X co o rd in a te
10. Y co o rd in a te
11. p rod u ct XY2
12. X co o rd in a te squared2
13. Y co o rd in a te squared
104
5 . Based upon th e dependent v a r ia b le w ith in th e d i s t r i c t , th e number
o f m ines p er c e l l , tren d s u r fa c e a n a ly s is were computed. The
program u t i l i z e d was F ortran IV o f th e Kansas G e o lo g ic a l Survey
> (O’Leary and o th e r s , 1965) .
M u lt ip le R eg ressio n A n a ly s is
C onceptual Framework
No attem pt i s made in t h i s ch ap ter to g iv e a d e t a i l e d , m athem ati
ca l e x p o s it io n o f th e t h e o r e t ic a l p r in c ip le s in v o lv e d w ith t h is typ e o f
a n a ly s i s . T h ere fo re , in t h i s paper, o n ly th e b a s ic co n cep ts are g iv e n in
a gen era l manner.
The d e f in i t i o n o f m u lt ip le r e g r e s s io n a n a ly s is i s g iv en by th e
S t a t i s t i c a l Package fo r the S o c ia l S c ie n c e s (SPSS) (1 9 7 5 , p . 321) as
f o l lo w s : " M u ltip le r e g r e s s io n i s a g en era l s t a t i s t i c a l tech n iq u e through
which one can a n a ly se th e r e la t io n s h ip betw een a dependent o r c r i t e r io n
v a r ia b le and a s e t o f independent o r p r e d ic to r v a r ia b le s ." The g en era l
form ula o f a m u lt ip le r e g r e s s io n i s a l in e a r fu n c t io n o f th e form:
V = b0 . b lXl * b 2X2 ♦ • • • bnXn
where th e X’s are th e independent v a r ia b le s th a t are r e la t e d to Y by th e
fu n c t io n a l form and th e c o e f f i c i e n t s , th e b ' s , o f th e X’s .
In o rd er to c l a r i f y t h i s co n cep t, we w i l l d e f in e a s im p le r e g r e s
s io n c a se o f two v a r ia b le s , which shows th e b a s ic p r in c ip le o f r e g r e s s io n
a n a ly s is , and t h is undoubted ly can be extended to c a se s in v o lv in g th r e e
o r more v a r ia b le s .
105
In sim p le r e g r e s s io n a n a ly s i s , v a lu e s o f th e dependent v a r ia b le
are p r e d ic te d from a l in e a r fu n c tio n o f th e form:
y = b 0 + b j X j
where th e Y' i s th e p r e d ic te d v a lu e o f th e dependent v a r ia b le , Y; b^ i s a
co n sta n t by which a l l v a lu e s o f th e independent v a r ia b le , X^, are
m u lt ip lie d ; and b^ i s a co n sta n t which i s added to each c a s e . The f i t t e d
l i n e w i l l c r o ss th e Y -a x is a t p o in t b^ (th e in te r c e p t ) and w i l l have a
s lo p e b^ (F igu re 3 9 ) .
The d if f e r e n c e betw een th e a c tu a l and th e e s tim a ted v a r ia b le , Y,
fo r each ca se i s c a l le d th e r e s id u a l , i . e . , th e e r r o r in p r e d ic t io n . I t
i s ex p ressed by th e form:
R esidual = Y - Y *
The r e g r e s s io n s t r a te g y in v o lv e s th e s e l e c t io n o f b^ and b^ in
such a way th a t th e sum o f th e squared r e s id u a ls i s sm a lle r than any
p o s s ib le a l t e r n a t iv e p o s it io n in g o f th e l i n e . T h ere fo re , s in c e th e sum
o f th e squared r e s id u a ls i s m inim ized , th e r e g r e s s io n l i n e i s c a l le d th e
" le a s t -sq u a r e s l in e " o r th e l i n e o f " b e st f i t . " This c h a r a c t e r i s t ic i s
rep resen ted by th e e x p r e ss io n :
E ( Y - Y ' ) ^ = S S = minimumr e s
There are th r e e term s which ex p ress th e v a r ia t io n o f th e depen
dent v a r ia b le . The f i r s t o f th e s e i s ex p la in e d o r measured by th e re g r e s
s io n l i n e , denoted by th e sum o f squares due to r e g r e s s io n :
SSreg Z Y '2 (ZjV =n Z (Y* - Y)2
Y -a x is
r e g r e s s io n l in e
o b se r v a tio n s
X -ax is
F igure 39 . Schem atic R ep resen ta tio n o f th e V a r ia b le s in a S im ple R eg ress io n A n a ly s is .
107
The secon d m easure o f v a r ia t io n r e fe r s to th o se u n exp la in ed by
th e r e g r e s s io n l i n e , denoted by th e sum o f sq uares due to r e s id u a ls
( d e v ia t io n s ) :
SSres = 2 CY - Y' ) 2
The th ir d measure o f v a r ia t io n i s th e r e la t io n s h ip betw een th e
ex p la in ed and u n exp la in ed v a r ia t io n s by th e r e g r e s s io n l i n e , and i s
measured by th e t o t a l sum o f sq u a r e s :
SST = Z Y2' - — =. Z (Y - Y)2
T h erefo re , t h i s r e la t io n s h ip i s ex p ressed by the form:
SST * SSr=g + SSr=s
or
Z (Y - Y )2 = Z (Y* - Y )2 + Z (Y - Y ' ) 2
The "goodness o f f i t " o f th e l i n e to th e p o in ts can be d e fin e d by
th e r a t io o f ex p la in e d v a r ia t io n in th e dependent v a r ia b le , Y, to th e
t o t a l v a r ia t io n in Y:
>2 - SSre g
O ften , th e R term i s ex p ressed as a p e r c e n ta g e . A nother u s e fu l
r e la t io n i s th a t th e square r o o t o f goodness o f f i t i s th e " m u ltip le
c o r r e la t io n c o e f f i c i e n t ," R:
r = /" i? " = f .
In o rd er to t e s t "how good" i s th e r e g r e s s io n , th e v a r ia n ce and
d egrees o f freedom are combined fo r o b ta in in g th e mean sq u a r e s , MS,
108
param eter. The v a r ia n c e betw een th e sam p les, in p a r t ic u la r S S ^ g , s ^r e g>
and SS^, can be used fo r t h is p u rp ose . In t h i s way, th e fo llo w in g
measures are determ ined:
v a r ia n ce among MS6 reg
SSre gm - 1
SST 6 Sv a r ia n c e w ith in MS = »-------re s N - m
where m = number o f v a r ia b le s , N = number o f sa m p les , and th e d egrees o f
freedom = th e number o f sq uares minus th e number o f independent l in e a r
r e s t r i c t io n s im posed upon th e q u a n t i t ie s in v o lv e d .
The s ig n i f ic a n c e o f th e v a r ia b le s w ith in th e eq u ation can be
t e s t e d by th e F r a t io :
res
Based upon t h i s r a t i o , th e c a lc u la te d F v a lu e can be t e s t e d w ith
th e t h e o r e t i c a l v a lu es from s t a t i s t i c a l ta b le s a t th e l e v e l o f s i g n i f i
cance d e s ir e d and a t th e number o f d egrees o f freedom in v o lv e d . F in a l ly ,
th e se v a lu e s are compared in ord er to a ccep t or t o r e j e c t th e N u ll
h y p o th e s is o f:
H
1
: B = 0
: B M 0
C onsequently , from t h i s con cep t i t i s p o s s ib le to e s t im a te w hether
or n o t th e r e g r e s s io n eq u a tio n i s s i g n i f i c a n t fo r th e proposed m odel.
109
R esu lts o f A n a ly s is
A ccording to th e c r i t e r i a o f th e r e g r e s s io n a n a ly s is p r e v io u s ly
d e sc r ib e d , th e b a s ic l in e a r eq u a tio n o f th e Alamos M ining D i s t r i c t was
e s ta b lis h e d as fo llo w s :
m ines = rock typ e + f r a c tu r in g + age + co o rd in a te s
A ll th e v a r ia b le s are l i s t e d in T able 2 .
I t must be p o in te d ou t t h a t , in t h i s s tu d y , a mine in c lu d e s a l l
k in d s, from sm all p r o sp e c ts to mines o f s e v e r a l l e v e l s . T h ere fo re , no
d is t in c t io n i s made on d e p o s it s i z e .
In o rd er to look fo r th e b e s t e s t im a tio n o f number o f m in es, Y ',
some arrangem ents o f th e independent v a r ia b le s w ith in th e r e g r e s s io n
eq u ation w ere combined. F i r s t , o n ly g e o lo g ic v a r ia b le s were computed.
Second, g e o lo g ic and geograp h ic (c o o r d in a te s ) v a r ia b le s , in c lu d in g
q u a d ra tic c o o r d in a te s , w ith in th e eq u ation w ere in c lu d e d . F in a l ly , in
ord er to a n a ly ze th e s ig n i f ic a n c e o f each v a r ia b le w ith in th e e q u a tio n ,
s te p w ise r e g r e s s io n was em ployed.
A summary o f th e computed c a lc u la t io n s fo r th e m u lt ip le r e g r e s
s io n eq u ation i s g iv e n . Appendix B in c lu d e s th e c a lc u la t io n s in d e t a i l .
S ig n if ic a n c e o f V a r ia b le s . T able 3 shows th e s ig n i f ic a n c e o f
each v a r ia b le w ith in th e r e g r e s s io n e q u a tio n .
From th e s e d a ta , i t i s in d ic a te d th a t f i r s t th e in t r u s iv e ande
s i t e , and s e c o n d ly , th e m etased im en ts, and then NW, HE, and EW fr a c tu r e s
are th e most im portant v a r ia b le s in th e r e g r e s s io n eq u a tio n . T h erefo r e ,
i t seems l i k e l y th a t th e s e g e o lo g ic f e a tu r e s are in t im a te ly r e la t e d to
th e emplacement o f th e o re b o d ie s in th e d i s t r i c t .
110
Table 3 . S ig n if ic a n c e o f V a r ia b le s in th e M u ltip le R egression Equation fo r th e Alamos M ining D i s t r i c t .
V a ria b le
Code in th e Computer Program
S ig n if ic a n c e
Each V ariab le A ll Equation
A nd esite* ANT 50 .5 5 8 5 0 .5 5 8
M etasedim ents MET 16.655 36 .474
MW fr a c tu r e s NWEST 8 .042 28 .247
NE fr a c tu r e s NEAST 4 .9 5 8 23 .041
G ranite GR 2 .9 6 3 19.263
EW fr a c tu r e s EWEST 2 .1 2 3 16 .567
Q uadratic X co o rd in a te X2 1 .126 14.409
Q uadratic Y co o rd in a te Y2 .461 12 .614
Y co o rd in a te Y .465 11 .218
V olcan ic rocks** VOLC .284 10 .069
Product X-Y co o rd in a te XY .109 9 .1 0 0
X co o rd in a te X .176 8 .3 0 3
Age AGE n o t in th e eq u ation
*In c lu d es Laramide p o r p h y r it ic a n d e s ite and C retaceous v o lc a n ic a n d e s it e s .
**In clu d es o n ly v o lc a n ic T e r t ia r y ro ck s .
I l l
S t a t i s t i c a l R e s u l t s ♦ These param eters w ere e s tim a ted on
M u ltip le r e g r e s s io n .66305
C o e f f ic ie n t .43964
Standard d e v ia t io n .62944
D egrees o f freedom : r e g r e s s io n 12
r e s id u a l 127
S ig n if ic a n c e o f m u lt ip le r e g r e s s io n , F 8 .30333
T h e o r e t ic a l F v a lu e a t 1% o f s ig n i f ic a n c e 2 .3 3545
By comparing th e s e v a lu e s , i t i s ob v iou s th a t th e c a lc u la te d F
v a lu e does n o t l i e w ith in th e r e g io n o f accep ta n ce fo r th e N u ll
h y p o th e s is i s r e j e c t e d . Thus, th e a l t e r n a t iv e h y p o th e s is , H^, i s
a c c e p te d :
H1 : b V h 2 ’ •• •> bn 0
T h erefo re , t h is prem ise in d ic a te s th a t th e r e g r e s s io n eq u a tio n
i s s i g n i f i c a t i v e , even though i t e x p la in s o n ly 44% o f th e v a r ia n c e in
number o f m in es .
P r e d ic te d Number o f Mines (Y1) . T able 4 shows th e s p a t ia l d i s t r i
b u tio n by c e l l o f both th e ex p ected number o f mines and th e known mines
in th e d i s t r i c t . From th e se d ata i t i s em phasized th a t:
Known mines 43
E xpected m ines 26
T ota l mines 69
E s tim a t io n i n d i c a t e s t h a t th e Alamos M ining D i s t r i c t s t i l l h a s a
60.5% e x p lo r a t io n p o t e n t i a l i n a d d i t io n t o th e known o re b o d ie s .
112
T able 4 . S p a t ia l D is tr ib u t io n by C e ll o f Known and P re d ic ted Mines fo r th e Alamos M ining D i s t r i c t .
Known P r e d ic te d Known P re d ic ted
C e llMines
0 0Mines(Y'D
T o ta l(Y+Y*) C e ll
Mines0 0
Mines(Y»)
T o ta l(Y+Y')
4 1 1 55 2 25 1 1 56 1 16 1 1 59 1 17 1 1 66 2 28 1 1 67 1 1 29 1 1 68 4 4
10 1 1 69 1 111 1 1 76 2 217 1 1 77 5 518 1 1 78 3 319 1 1 79 1 120 1 1 80 1 121 1 1 81 1 127 3 3 86 2 228 3 3 87 2 229 2 2 88 1 1 233 1 1 90 1 134 1 1 96 1 135 1 1 97 2 246 1 1 106 1 1 248 1 1 127 1 149 1 1 129 1 150 1 1 152 1 1
T o ta ls 43 26 69 •
E x p lo ra tio n p o t e n t ia l in th e d i s t r i c t i s 60.5% in a d d it io n to th e known o re b o d ie s .
113
Based upon th e s e r e s u l t s , th e most im portant areas fo r e x p lo r a
t io n are S ie r r a de Alam os, c e l l s 67 and 6 9 , and e s p e c ia l ly c e l l s 87 , 9 7 ,
and 106; and th e area o f P ied ra s V erdes, c e l l s 1 7 , 18 , and 19
(F igu re 4 0 ) .
I t i s b e l ie v e d , accord in g t o th e g e o lo g ic f e a tu r e s p r e v io u s ly
m entioned in Chapter 3 , th a t th e s e areas are co n s id ered a ls o o f v i t a l
im portance by s u b je c t iv e g e o lo g ic r ea so n in g . T h erefo re , i t i s e v id e n t
th a t both th e q u a n t ita t iv e and th e g e o lo g ic methods agree th a t th e se
areas are th e b e s t ' ta r g e t s fo r fu tu r e e x p lo r a tio n w ith in th e Alamos
D i s t r i c t .
Trend S u rfa ce A n a ly s is
C onceptual Framework
D avis (1 9 7 3 , p . 457) d e f in e s a tren d su r fa c e as fo llo w s : "A
tren d may be d e fin ed as a l in e a r fu n c t io n o f th e geograp h ic co o rd in a te s
o f a s e t o f o b se r v a tio n s so c o n str u c te d th a t th e squared d e v ia t io n s from
th e tren d a re m in im ized ."
A lso , th e same author co n s id e r s th a t t h i s con cep t in v o lv e s th r e e
fundam ental p a r ts :
1. A tren d su r fa c e i s based upon th e " geograp h ic co o rd in a tes" which
im p lie s th a t an o b se r v a tio n i s a fu n c t io n o f i t s geograp h ic
lo c a t io n .
2 . A tren d su r fa c e i s a " lin e a r fu n ctio n " o f th e e x p r e ss io n
Y = b 1X1 + b 2X2 + . .
109° 10' v 1 0 9 °0 0 ‘1 ......... ...... 1 I ---- * L ' _ . : - r ; I
1 2 3 4Mocuzon
6 7 C 9 10
-27° 10"
-27°00'
11 12 13 14 15 16HmH 20
21 22 23 24 25 26 27 -A. 28PiedrosVerdes
29 30
31 32 33 34 35 36 3 7 38 39 40
41 42 4 3 44 45 46 47 48 4 9 5 0
51 52 53 54 5 5 56 57 58
MinosNucvas
59 6 0
61 62 63 64 65 66■ v 60
d
70
71 72 fit- Ooli so
73 74 75 76 77 76 79 # 3Aiuinoi,
81 62 83 84 8 5 66
i
66 8 9 j 5 :
91 92 93 94 95 961 93 9 9 ICO
101 102 103 104 105p i
107 103 109 110
111 112 113 114 115 116 117 118 119 120
121 122 123 124 125 126 127 126 12 9 130
131 132 133 134 13b 136 137 138 • 139 140
o _____ 5 10
kilometers
F ig u re 40
115
where th e b ' s are c o e f f i c i e n t s and th e X 's are some com binations
o f th e geograp h ic c o o r d in a te s . From t h is eq u a tio n th e tren d
com ponents, Y ' , on an o b se r v a tio n are e s t im a te d .
3. L in ear fu n c tio n s "m inim ize th e squared d e v ia t io n s from th e tren d ."
T h erefo re , th e tren d l i n e co n ta in s th e s m a lle s t v a r ia n c e about i t .
C onseq u en tly , from th e s e c o n c e p ts , i t can b e seen th a t funda
m en ta lly th e t h e o r e t ic a l a sp e c ts o f th e tren d su r fa c e tech n iq u es are
based upon th e same t h e o r e t ic a l p rem ises o f the r e g r e s s io n a n a ly s is
a lread y d e sc r ib e d .
B a s ic a l ly , th e purpose o f a trend s u r fa c e a n a ly s is i s to se p a r a te
map d ata in to two com ponents, th a t o f " reg io n a l nature" and " lo c a l
f lu c t u a t io n s ."
The r e g io n a l component u s u a l ly i s r e la t e d to th e l in e a r fu n c tio n
o f th e form:
♦ V l * b 2X2
where Y i s a g e o lo g ic o b se r v a t io n , b^ i s a c o n sta n t v a lu e r e la t e d to th e
mean o f th e o b s e r v a t io n s , b^ i s th e c o e f f i c i e n t o f th e e a s t -w e s t
co o rd in a te and b^ i s th e c o e f f i c i e n t o f th e n o r th -so u th c o o r d in a te .
In order to sea rch fo r s p e c i f i c lo c a l f lu c t u a t io n s , th e b a s ic
model o f th e l in e a r fu n c t io n ( f i r s t degree eq u ation ) i s u s u a l ly expanded
to p olynom ial fu n c tio n s to th e seco n d , th ir d , o r h ig h e r o r d e r s . There
fo r e , each geograp h ic v a r ia b le i s s im p ly r a is e d to a h ig h e r power,
c r e a t in g new v a r ia b le s . T his l in e a r eq u ation i s o f th e e x p r e ss io n :
Y = b 0 + V l + b2x2 + V l 2 * » 4 X22 + • • • * V "
I t i s em phasized th a t th e polynom ial fu n c tio n s are u sed fo r
g e o lo g ic tren d a n a ly s is m erely as a m atter o f con ven ience and as a
s u b je c t iv e method fo r a b e s t f i t o f th e d is t r ib u t io n .
R e su lts o f A n a ly s is
As p r e v io u s ly m entioned , in ord er t o compute th e tren d s u r fa c e
fo r th e Alamos D i s t r i c t , th e number o f mines p er c e l l was determ ined
(dependent v a r ia b le ) .
With th e goa l o f e s t im a tin g th e r e g io n a l and lo c a l v a r ia t io n s o f
th e tren d su r fa c e in th e area due to mines lo c a t io n , eq u a tio n s o f f i r s t ,
seco n d , and th ir d degree w ere computed. The b a s ic l in e a r fu n c tio n was
e s ta b lis h e d o f th e form:
mines = NS c o o rd in a te s + EW co o rd in a te s
o r
Z = X + Y
By u t i l i z i n g th e computer program fo r tren d su r fa c e a n a ly s is o f
th e Kansas G e o lo g ica l Survey (O 'Leary and o th e r s , 1 9 6 5 ) , th e fo llo w in g
e s t im a tio n s fo r th e Alamos M ining D i s t r i c t w ere o b ta in e d . Appendix C
shows th e c a lc u la t io n in d e t a i l .
116
C o e f f ic ie n t s o f C o r r e la tio n
1 s t Degree 2nd Degree 3rd Degree
r2% .1486 .2261 .3142
R .3855 .4755 .5605
S t . Dev .79 .7 6 .71
117
By exam ining th e s e v a lu e s , i t i s c le a r th a t th e l e v e l o f
ex p la in ed v a r ia n c e (R %) i s o n ly 15% in th e f i r s t degree eq u a tio n and
th a t t h is v a lu e in c r e a se s to 31.4% in th e th ir d degree e q u a t io n . T here
fo r e , i t appears th a t a h igh degree eq u ation su g g e s ts a b e t t e r model fo r
th e mines d is t r ib u t io n w ith in th e d i s t r i c t .
In a n a ly z in g th e p lo t s o f th e f i r s t , seco n d , and th ir d d egree
eq u a tio n s , i t seems l i k e l y th a t both r e g io n a l and lo c a l s t r u c tu r a l
fe a tu r e s are a s s o c ia te d w ith th e tren d su r fa c e a n a ly s is .
The p lo t o f th e f i r s t degree eq u a tio n (F igu re 41) appears to be
a s s o c ia te d w ith th e n o r th w e ste r ly r e g io n a l tren d o f fr a c tu r in g . In
a d d it io n , i t shows an increm ent toward th e n o r th e a s t which i s th e lo c a l
system o f fr a c tu r in g in th e a rea .
The p lo t o f th e second degree eq u ation (F ig u re 42) in d ic a te s a
c lo s e a s s o c ia t io n w ith th e lo c a l d is t r ib u t io n o f m ines w ith in th e S ie r r a
de Alamos and P ied ras Verdes areas w hich , acco rd in g to th e m u lt ip le
r e g r e s s io n a n a ly s is and s u b je c t iv e g e o lo g ic a l r e a so n in g , are th e b e s t
areas fo r fu r th e r e x p lo r a tio n .
The p lo t o f th e th ir d degree eq u ation (F ig u re 43) shows a b e t t e r
a s s o c ia t io n w ith the lo c a l d is t r ib u t io n o f mines and s t r u c t u r e s . I t i s
more r e s t r i c t i v e and in d ic a te s th a t th e b e s t areas fo r p r o sp e c t in g are in
th e c e n tr a l p a r t o f S ie r r a de Alamos and th e P ied ras Verdes a rea . I t i s
in t e r e s t in g t o n o te th a t both th e tren d s u r fa c e and th e r e g r e s s io n
a n a ly s is c o in c id e in th e e s t im a te d areas f o r e x p lo r a tio n and s p e c i f i c a l l y
c e l l s 1 7 , 1 8 , 19 , 67, 69 , 87 , 9 7 , and 106 (F ig u re 4 4 ) . Furtherm ore, th e
p lo t o f th e th ir d degree shows th a t th e s tr u c tu r a l fe a tu r e s are
118
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F igure 42 . P lo t o f Second Degree E quation , Trend S u rface A n a ly s is .
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121
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kilom eters
F igu re 4 4 . L ocation o f H ig h est P r io r i t y P r o sp e ctin g A reas A ccording toTrend S u rface A n a ly s is .
122
in t im a te ly a s s o c ia te d w ith th e geom orphologica l p ro v in ce in w hich th e
Alamos D is t r ic t l i e s , th a t i s th e B asin and Range S ubprovince. T his
fe a tu r e i s in d ic a te d by th e low v a lu e s in th e v a l le y s and h igh v a lu e s
in th e r i d g e s . Appendix B shows in d e t a i l some o f th e computed
o p e r a t io n s .
I t i s b e l ie v e d , th a t th e r e s u l t s o b ta in ed from th e s e s t a t i s t i c a l
tech n iq u es are o n ly th e e a r ly s ta g e in a com prehensive e s t im a tio n o f th e
e x p lo r a tio n m ineral p o t e n t ia l w ith in th e Alamos D i s t r i c t .
CHAPTER 5
CONCLUSIONS AND RECOMMENDATIONS
A ccording to th e p re lim in a ry r e s u l t s o f th e g e o lo g ic a l e x p lo r a
t io n c a r r ie d ou t in th e Alamos M ining D i s t r i c t , Sonora, M exico, i t i s
b e lie v e d th a t th e fo llo w in g c o n c lu s io n s can be made:
1 . The Alamos D i s t r i c t has been p r a c t ic a l ly in a c t iv e s in c e 1915.
N e v e r th e le s s , the reason was n o t fo r la ck o f m in e r a liz a t io n b u t a
r e s u l t o f p o l i t i c a l problem s in th e cou n try .
2 . The d i s t r i c t ' s p a s t p rod u ction i s e s t im a ted a t 150 m il l io n
d o l la r s . T h is amount, by i t s e l f , g iv e s th e d i s t r i c t im portance.
3 . The Alamos D i s t r i c t l i e s in th e Epitherm al P recio u s-M eta l
P rovin ce o f n o rth w est M exico, a m in e r a lo g ic a l- s tr u c tu r a l u n it
1 ,0 0 0 k ilo m e ters lo n g , one o f th e r ic h e s t s i l v e r p ro v in ce s in th e
w orld .
4 . S tr u c tu r a l and l i t h o l o g i c a l c o n d it io n s appear t o have been th e
c h ie f fa c to r s th a t c o n tr o lle d th e d e p o s it io n o f hydrotherm al
s o lu t io n s ' w ith in th e p re-m in era l fr a c tu r e s w hich c o n tr o lle d th e
o re em placem ent.
5 . U n t il d a te , 108 p r o s p e c ts , ran gin g from sm a ll tren ch es to m ines
w ith s ix t e e n l e v e l s , have been v i s i t e d . Among th e s e m ining
w o rk in g s, n in e p ro sp e c ts are co n sid ered th e most p rom isin g o n e s .
They are ranked in ord er o f t h e ir lo c a t io n , a c c e s s i b i l i t y , and
123
mine c o n d it io n s : San Manuel, P lom osas, O ta te s , Ana M aria,
Prom ontorio, Q u in tera , Santo Domingo, Japon en M exico, and Minas
N uevas.
6 . The o r e , w ith some v a r ia t io n s in r a t io , i s m in e r a lo g ic a l ly s im i
la r among th e ore b o d ie s in th e d i s t r i c t . The prim ary m in era ls
in c lu d e g a le n a , t e t r a h e d r i t e , c h a lc o p y r ite , s p h a le r i t e , a r g e n t i t e ,
p y r i t e , and n a t iv e s i l v e r w ith in q u artz as a gangue m in era l.
7 . To d a te , th e San M anuel, Ana M aria, Prom ontorio, Q u in tera , and
Japon en Mexico mines are a c t iv e , b u t th e m ining o p e r a tio n s are
r e s t r i c t e d to dumps and some p i l l a r s due t o th e la c k o f m ining
equipm ent. T h ere fo r e , th e p ro d u ctio n i s s m a ll, ran g in g from 60
to 120 ton s p er month.
8 . The San Manuel, P lom osas, Ana M aria, O ta te s , and Japon en
Mexico are new m ining p r o sp e c ts in w hich o n ly l im ite d underground
e x p lo r a tio n has been accom p lished . T h erefo re , th e s e p r o sp ec ts
are o f easy underground a c c e s s . On th e o th e r hand, th e
Prom ontorio, Q u in tera , Santo Domingo, and Minas Nuevas p r o sp e c ts
are o ld mines w hich reach from 115 to 450 m eters in d ep th . The
a c c e ss to th e s e m ines i s l im it e d o n ly to th e sh a llo w mine
w orkings due to mine c o n d it io n s .
9 . D e ta ile d sam pling from th e n in e p ro sp ec ts shows a combined
average grade o f s i l v e r 400 grams p er to n , g o ld 0 .6 5 grams p er
to n , le a d 2.88%, z in c 3.38%, and copper 0.67%.
1 0 . A ccord ing to th e l im it e d underground w ork in gs, underground
m apping, and g e o lo g ic f a v o r a b i l i t y , in th e n in e p r o s p e c ts , a
c o n se r v a t iv e e s t im a te o f th e o re r e se r v e s i s :
124
125
proven r e se r v e s 32 ,000 m e tr ic to n s
p robab le r e se r v e s 181 ,000 m e tr ic ton s
p o s s ib le r e se r v e s 490 ,0 0 0 m e tr ic ton s
In a d d it io n to th e s e o re r e s e r v e s , th ere i s an area o f " p o te n t ia l
ore r e ser v es" among th e o ld mines ("Mother lode" s t r u c t u r e ) ,
which i s e s t im a te d a t 1 ,0 0 0 ,0 0 0 m etr ic to n s .
11. Economic c o n s id e r a t io n s accord in g to th e cu rren t m etal q u o ta t io n s ,
n e t sm e lte r r e tu r n , e x p lo i t a t io n , and p rod u ction c o s t s show:
g ro ss v a lu e o f o re in p la c e $116 .80 p er m e tr ic to n
t o t a l c o s t o f o p e r a tio n $ 30 .00 p er m e tr ic ton
n e t sm e lte r re tu rn $ 5 8 .5 0 p er m e tr ic ton
12. P r o f i t a b i l i t y a n a ly se s a cco rd in g to v a r io u s methods o f econom ic
e v a lu a tio n tech n iq u es in d ic a te advantageous econom ic r e s u l t s .
They are c a lc u la te d a s:
n e t p r e se n t v a lu e @ 25% d isc o u n t r a te $ 5 5 2 ,4 0 0 .0 0
d isco u n ted cash flow re tu rn on in vestm en t 36.67%
payback p e r io d 3 .2 y ea rs
p r e se n t v a lu e r a t io @ 25% 0 .4 4 4
a ccou n tin g r a te o f re tu rn 30.40%
13 . Both econom ic and p r o f i t a b i l i t y a n a ly se s are b ased upon th e
o u t lin e d e x p lo r a tio n and developm ent program, w hich e s t im a te s
th a t a t l e a s t 500 ,000 m e tr ic tons cou ld be proven d u rin g such a
proposed program. The l i f e o f mine o p e r a tio n s i s e s tim a ted as a t
l e a s t 8 y ea rs o f p rod u ction a t a r a te o f 200 m e tr ic to n s /d a y .
The t o t a l c a p it a l in vestm en t o f t h i s m ining v en tu re i s e s t im a ted
a t 2 m il l io n d o l la r s .
14 . G e o s t a t i s t ic a l a n a ly s is , m u lt ip le r e g r e s s io n a n a ly s is and tren d
su r fa c e te c h n iq u e s , in d ic a te th a t th e d i s t r i c t has s t i l l 60%
e x p lo r a tio n p o t e n t ia l in a d d it io n to th e known ore b o d ie s . The
b e s t e s tim a ted areas fo r e x p lo r a tio n are th e c e n tr a l p a r t o f
S ie r r a de Alam os, j u s t sou th o f th e very im portant o ld m ines o f
th e d i s t r i c t ; and th e P ied ras Verdes a rea , 15 k ilo m e te r s n orth o f
S ie r r a de Alamos.
The o u t ly in g d i s t r i c t s are n ot in c lu d ed b ecau se no e x p lo r a -
work has been done so fa r .
Based upon th e above c o n c lu s io n s , i t i s s tr o n g ly recommended th a t
t h i s program be fo llo w e d w ith th e ex p lo ra tio n -d ev e lo p m en t program. The
purpose o f t h i s program i s tw o - fo ld . F i r s t , to e v a lu a te and to con firm
th e p o s s ib le ore e x te n s io n in depth w ith in th e n in e p r o sp e c ts a lrea d y
d e sc r ib e d . Second, to search fo r new ore b o d ie s , e s p e c ia l ly in th e
s tr u c tu r e o f th e Prom ontorio, Q u in tera , and Santo Domingo m in es, and in
th e areas e s t im a ted t o be g e o s t a t i s t i c a l l y fa v o r a b le .
The n e x t phases recommended are:
1 . D r i l l in g from su r fa c e and underground as w e ll as underground
e x p lo r a tio n w orkings in th e n in e mines m entioned . The c o s t o f
t h i s program phase i s e s t im a ted to c o s t $ 3 5 0 ,0 0 0 .0 0 during a
p e r io d o f a t l e a s t 18 m onths.
2 . A geochem ical su r v e y , in c lu d in g ch ip rocks and s o i l sam ples
p erp en d icu la r to th e b ea r in g o f th e "Mother lode" s tr u c tu r e as
126
127
w e ll as in th e areas o u t lin e d by th e r e g r e s s io n and tren d s u r fa c e
a n a ly s is , c e l l s 6 7 , 6 9 , 87 , 9 7 , and 106. The tim e o f t h is phase
i s e s t im a te d to be 3 months a t a c o s t o f $ 1 0 ,0 0 0 .0 0 .
3 . G eophysica l in v e s t ig a t io n s (TURAM) p erp en d icu la r to th e s tr u c tu r e
among th e Prom ontorio, Q u in tera , and Santo Domingo m ines
("Mother lode" s t r u c t u r e ) . The tim e o f t h i s program 's phase i s
c a lc u la te d a t 3 months a t a c o s t o f $ 2 0 ,0 0 0 .0 0 .
4 . At th e p r e se n t t im e , i t i s n ot recommended th a t e x p lo r a tio n
su rveys b e conducted in th e P ied ras Verdes a rea , b ecau se a
p r iv a te company (TRION) i s e v a lu a t in g and e x p lo r in g th e area in
d e t a i l .
APPENDIX A
ECONOMIC CONSIDERATIONS FOR THE PROSPECTS IN THE ALAMOS
MINING DISTRICT EXPLORATION PROGRAM, 1973-75
128
T able A .1 Average Grade and Ore V alue b e fo r e C oncen tration a t th e Alamos D i s t r i c t .
P ro sp ectNo. o f Samples
S i lv e r(gm /ton)
Gold(gm /ton)
Lead(%)
Zinc(%)
Copper(%)
Gross V alue o f Raw Ore Per M etr ic Ore*
Prom ontorio 25 325 0 .4 4 .0 8 .0 0 .3 142 .80
Q uin tera 14 600 0 .3 1 .5 1 .6 2 .0 13 7 .6 0
Santo Domingo 8 500 0 .2 2 .7 0 .9 0 .2 9 8 .5 0
Minas Nuevas 4 250 0 .4 3 .0 1 .0 0 .2 6 5 .3 0
O ta tes 15 125 0 .6 4 .5 4 .6 0 .8 9 4 .9 5
Plom osas 15 100 0 .5 5 .5 4 .5 1 .0 122 .00
Ana Maria 30 200 0 .5 2 .8 3 .0 0 .5 7 8 .8 5
Japon en M exico 8 900 9 .0 2 .0 18 .0 0 .1 345 .5 0
San Manuel 10 250 1 .0 1 .8 2 .9 0 .7 8 5 .6 0
♦P ercen tage rec o v ery and grade o f c o n cen tra te n o t co n s id e r e d . P r ic e s accord in g to E. M. J . , June 1975:
S i lv e r @ $ 4 .5 3 /t r o y o z . Z inc @ $ 0 .389/pound
Gold @ $ 1 6 7 .2 5 /tr o y o z . Copper @ $ 0 .63/pound
Lead @ $ 0 .233/pound
129
130
T able A .2 Ore R eserves E stim ate fo r th e P ro sp ects in th e Alamos M ining D i s t r i c t .
P ro sp ect Proven Probable P o s s ib le T o ta l
Prom ontorio 5 ,0 0 0 16,000 100,000 121,000
Q uin tera 6 ,0 0 0 20 ,000 5 0 ,0 0 0 76 ,000
Q uin tera dump 10 ,000 25 ,000 35 ,0 0 0
Santo Domingo ? 18 ,000 200 ,000 218 ,000
Minas Nuevas ? 18,000 5 0 ,0 0 0 6 8 ,0 0 0
San Manuel 4 ,0 0 0 17 ,500 3 0 ,0 0 0 51 ,5 0 0
O tates 1 ,200 6 ,0 0 0 10,000 17 ,200
Plom osas 1 ,2 0 0 9 ,5 0 0 20 ,0 0 0 3 0 ,7 0 0
Ana Maria 3 ,0 0 0 16 ,000 30 ,0 0 0 49 ,0 0 0
Japon en Mexico 1 ,5 0 0 5 ,0 0 0 10 ,000 16 ,500
S u b-T ota l 3 1 ,9 0 0 183,000 4 9 0 ,000 682 ,900
T o ta l ore r e se r v e s e s t im a te = + 700 ,000 m e tr ic to n s
T able A .3 E stim ated Grade and Tonnage fo r th e P ro sp ec ts in th e Alamos Mining D i s t r i c t .
Name of Prospect
Average GradeAg
(gm/ton)Pb(* )
Zn(%)
Cu(*)
Au(gm/ton)
Estimated Tonnage 70% of Total Ore Reserves
Grade x Tonnage = MetalAg
(106gm/ton) (I0 6%) (106%) (103%) (JO^gra/ton)
Promontorio 325 4.1 8.0 0.3 0.4 85,000 27.6 34.9 68.0 25.5 34.0Quintera 600 1.6 1.6 2.0 0.2 75,000 45.0 12.0 12.0 150.0 37.5Santo Dominto 500 2.6 1.5 0.24 0.35 150,000 75.0 39.0 16.5 36.0 52.5Minas Nuevas 250 3.0 1.0 0.2 0.4 48,000 12.0 14.4 4.8 9.6 19.2San Manuel 250 1.8 2.9 1.0 1.0 36,000 . 9.0 6.5 10.5 56.0 36.0Otates 125 4.5 4.6 0.8 0.6 12,500 1.56 5.7 5.8 10.0 7.5Plomosas 100 ' 5.5 4.5 1.0 0.5 21,500 2.15 11.8 11.0 21.5 10.7Ana Maria 200 2.8 2.9 0.5 0.6 35,000 7.0 . 9.8 10.5 17.5 10.5Japon en Mexico 900 2.0 18.0 0.1 9.0 11,000 9.9 2.2 19.8 11.0 99.0
474,000 189.21 136.3 159.1 517.1 506.9010% d ilu tio n 47,000Estimated tonnage Recovery 90%
521.000470.000 Average metal tonnage quantity o f metal
quantity of ore
EXiWi
.Average grade 10% d ilu tio n :S ilv e r * 366 grams/ton Lead = 2.62%Zinc = 3.06%Copper .= 0.61%Gold = 0.60 grams/ton
Prelim inary average prince = $136.80 per m etric ton.
Average grade before d ilu tio n : S ilv e r = 400 grams/ton Lead — 2 • 87*6 Zinc = 5.38%Copper = 0.67%Gold = 0.65 grams/ton
131
T able A. 4 C ost and Time E stim a tes o f th e E x p lo ra tio n Program fo r th e P ro sp ects in th e Alamos M ining D i s t r i c t ( in Order o f P r i o r i t i e s ) .
D r i l l in g
P ro sp ect
M eters from Underground
Workings
C ost Per M eter
($)
UndergroundWorkings(m eters)
C ost Per M eter
($)Time
(months)T o ta l
($)
San Manuel 150 70 200 100 6 3 0 ,5 0 0 .0 0
Ana Maria 150 80 200 110 6 3 4 ,0 0 0 .0 0
O ta tes 100 70 150 100 4 2 2 ,0 0 0 .0 0
Plom osas 100 60 150 100 4 2 1 ,0 0 0 .0 0
Japon en Mexico 100 70 150 110 5 2 3 ,5 0 0 .0 0
Prom ontorio 150 75 200 120 6 3 5 ,2 5 0 .0 0
Q uin tera 150 75 200 120 8 3 5 ,2 5 0 .0 0
Santo Domingo 250 75 350 120 12 6 0 ,7 5 0 .0 0
Minas Nuevas 100 75 150 120 8 2 5 ,5 0 0 .0 0
2 8 8 ,7 5 0 .0 0
Overhead (10%) 2 8 ,8 5 0 .0 0
C ost o f th e g e o p h y s ic a l and geoch em ica l s tu d ie s 3 0 ,4 0 0 .0 0
T o ta l C ost o f E x p lo ra tio n $ 3 4 8 ,0 0 0 .0 0 132
133
T ab le A .5 D e te rm in a tio n o f th e O p e ra tin g C o s t o f M ining and M il l in g .
Mining C o s ts : In d o lla r s p er m etr ic ton (S o u rce : AIME, 1973, fo r 1969;C.M.M., 1972)
D ir e c t C o sts , Shrinkage S top in g 1 0 0 -1 ,2 5 0 T .P .D .
D ir e c t C o sts ,Cut and F i l l S to p in g
2 5 0 -1 ,0 0 0 T .P .D .
Development 0 .5 2 0 .8 9S to p in g 2 .9 0 3 .5 2H aulage 0 .4 8 0 .7 7H o is t in g 0 .5 2 0 .4 9Pumping 0 .0 7 0 .0 6V e n t ila t io n 0 .0 8 0 .0 5O ther 0 .9 0 2 .5 6General 2 .1 0 3 .5 8
T o ta l 6 .1 0 8 .0 6
C ost fo r 1975 and average = $15 . 00
M illin g and C on cen tratin g C o s ts : P r o c e ss in g c o s t s fo r 400 T .P .D . ind o lla r s p er m e tr ic ton (Source: AIME,1973)
Labor 2 .3 4S u p p lie sC hem icals 2 .5 4M aintenance 0 .8 6Other o p e r a tio n s 0 .6 2U t i l i t i e s 0 .2 2T ravel 0 .0 3O ther 0 .3 3
T o ta l 6 .9 4
C ost fo r 1975 and average = $1 0 .0 0
T o ta l C ost o f O peration:
C ost fo r 1975 m ining $1 5 .0 0C ost fo r 1975 m il l in g and co n c e n tr a tio n $10 .00
S u b-T ota l $ 2 5 .0 0Overhead (20%) $ 5 .0 0
T o ta l c o s t o f o p e r a tio n $3 0 .0 0
T able A .6 C a lc u la t io n o f th e Net S m elter Return on C on cen trates: S i lv e r , Lead, and Gold. — R atio o f co n cen tra tio n 1:20
134
Lead S i lv e r Gold
Grade o f ore 2.6% 366 gm/ton 0 .6 gm /tonR ecovery 83.0% 85.0% 85.0%Grade o f co n cen tra te 43.0% 6222 gm/ton 1 0 .0 gm /ton
M etalP r ic e
($)-D ed uction
in GradeC ontent
M etric Ton-D ed uction
P r ic ePayment
(%) N et
Lead .2 3 3 / lb 40% 880 lb .0 3 lb 95 169 .70
S i lv e r 4 .5 3 /o z 6222 g r /to n 200 oz .0 4 oz 95 853 .00
Gold 1 6 7 .0 0 /o z 9 g r /to n 0 .2 9 oz 92 4 4 .3 0
Return sm e lte r b e fo r e d ed u ctio n s 1067 .00
D ed u c tio n s:
F re ig h t (Chihuahua C ity ) 2 5 .0 0 M oisture probab ly 10% 2 .5 0 Base charge 2 5 .0 0
5 2 .5 0S e c u r ity fa c to r (30%) 15 .50
T o ta l d ed u ctio n s 6 7 .0 0
N et sm e lte r re tu rn on le a d , g o ld ,and s i l v e r co n c e n tr a te s 1000 .00
N ote: For con ven ien ce in c a lc u la t io n s , th e t o t a l reco v ery o f g o ld ands i l v e r are in c lu d ed in lea d c o n c e n tr a te s . A c tu a lly , a sm a ll amount o f them m ight appear in th e z in c c o n c e n tr a te s .
135
T able A .7 C a lc u la t io n o f th e N et Sm elter Return on C on cen trates: Z in c. — R atio o f co n cen tra tio n 1 :2 0 .
Grade o f ore = 3.0%; R ecovery = 80.0%; Grade o f co n cen tra te = 48.0%
P r ic e -D ed uction C ontent PaymentM etal ($) in Grade M etric Ton (%) N et
Zinc 0 .3 8 9 / lb 43% 946 lb 85 313 .00
Return sm e lte r b e fo r e d ed u ctio n s 31 3 .0 0
D eductions:
F re ig h t ( S a l t i l l o C ity ) 3 0 .0 0M oisture probab ly 8% 2 .5 0Base charge 5 3 .0 0Charge $ .9 0 fo r 1 c e n t above 12 .5$ 2 4 .0 0
109 .50S e c u r ity fa c to r (30%) 3 3 .5 0
T o ta l d ed u ction s 143 .00
Net sm e lte r retu rn on z in c c o n cen tra te 170 .00
T o ta l re tu rn p er m etr ic ton mined:
S i l v e r , le a d , and g o ld c o n cen tra te $1000 .00 Zinc c o n cen tra te 170 .00
T o ta l re tu rn on c o n c e n tr a te s $1170 .00
T o ta l re tu rn p e r ton mined r a t io o f c o n c e n tr a tio n 1:20 $ 5 8 .5 0
136
T able A .8 C a lc u la t io n o f th e Cash Flow fo r th e Alamos D is t r i c t .
Years
2 -8 9
Produced ton s 60 ,0 0 0 6 0 ,0 0 0
Gross revenue 3 ,5 1 0 ,0 0 0 3 ,5 1 0 ,0 0 0
L ess o p era tin g c o s t s 1 ,8 0 0 ,0 0 0 1 ,8 0 0 ,0 0 0
Gross earn in gs 1 ,7 1 0 ,0 0 0 1 ,7 1 0 ,0 0 0
Less d e p r e c ia t io n 150 ,000 150 ,000
B alance 1 ,5 6 0 ,0 0 0 1 ,5 6 0 ,0 0 0
L ess ta x p rod u ction and im port ta x (30%) 468 ,000 4 6 8 ,0 0 0
B alance 1 ,0 9 2 ,0 0 0 1 ,0 9 2 ,0 0 0
L ess s t a t e ta x (4%) 4 3 ,6 8 0 4 3 ,6 8 0
B alance 1 ,0 4 8 ,3 2 0 1 ,0 4 8 ,3 2 0
Less income ta x (42%) 4 4 0 ,294 440 ,294
N et income 608 ,025 608 ,025
P lu s d e p r e c ia t io n and a m o rtiza tio n 150,000 150 ,000
P lu s d e p le t io n (30% o f p rod u ction ) 140,400 140,400
Rec working c a p it a l 100 ,000
898,425 998 ,425CASH FLOW
137
T ab le A .9 E s t im a t io n o f th e N et P re s e n t V alu e .
D iscou n t RateYear Cash Flow 10% 25% P re se n t Value
0 - 4 0 0 ,000 1 .000 - 4 0 0 ,0001 -1 ,6 0 0 ,0 0 0 .909* -1 ,4 5 4 ,0 0 02 898,425 .640 574 ,9923 898,425 .512 459 ,9934 898,425 .410 368 ,3545 898,425 .328 294 ,6836 898,425 .263 235 ,3877 898 ,425 .210 188 ,6708 898 ,425 .168 150,9359 -9 8 ,4 2 5 .134 133,790
N et re tu rn v a lu e @ 25% $ 552 ,404
T able A .10 E stim a tio n o f th e D iscounted Cash Flow or In te r n a l Rate o f R eturn.
D iscou n t D iscou n tYear Cash Flow Rate (30%) NPV Rate (40%) NPV
0 - 4 0 0 ,000 1 .000 _ 400 ,000 1 .0 0 0 400 ,0001 . -1 ,6 0 0 ,0 0 0 .826* -1 ,3 2 1 ,6 0 0 .826* -1 ,3 2 1 ,6 0 02 898,425 .592 531 ,868 .510 458 ,1983 898 ,425 .455 408 ,783 .364 327 ,0264 898 ,425 .350 314 ,449 .260 233 ,5905 898,425 .269 241 ,676 .186 167 ,1076 898,425 .207 185,974 .133 119,4907 898 ,425 .159 142,850 .095 85 ,3508 898,425 .1 2 3 110,506 .068 61 ,0939 998 ,425 .0 9 4 9 3 ,8 5 2 .0 4 8 47 ,925
$ 298 ,958 $ -2 2 6 ,6 2 3
By in t e r p o la t in g . D iscou n ted Cash Flow = 35. 81%
*The r a te o f 10% i s c o n s id e r in g a f in a n c ia l loan from a bank
T a b le A .11 C a lc u la t io n o f th e P r e s e n t V alue R a tio
Year Cash FlowD iscou n t
Rate (25%) N et P resen t Value
0 - 400 ,000 1 .000 - 4 0 0 ,0001 -1 ,6 0 0 ,0 0 0 .800 -1 ,2 8 0 ,0 0 02 898,425 .640 574 ,9923 898,425 .512 4 5 9 ,9944 898,425 .410 368 ,3545 898,425 .328 2 9 4 ,6836 898 ,425 .262 253 ,3877 898,425 .210 188,6698 898,425 .168 150,9359 998 ,425 .134 133,789
-2 ,4 2 4 ,2 6 31 ,6 8 0 ,0 0 0
744 ,263
P resen t Value R a tio = ' g ^ o o o ' 4 .4 3
T able A. 12 C a lc u la t io n o f th e A ccounting Rate o f R eturn.
Average Annual A ccounting:
P r o f i t a f t e r , ta x = 4 ,8 6 4 ,2 0 0 _ ggg 0258 yea rs
A ccounting r a te o f re tu rn = Y "odo'doo = • 304 or
30.40% on th e in vestm en t
139
T ab le A .13 E s t im a t io n o f Pay Back P e r io d and R e tu rn o f In v e s tm e n t.
Pay Back P e r io d :
Year 2 898 ,425Y ear 3 1 ,7 9 6 ,8 5 0Year 4 2 ,6 9 5 ,2 7 5
By in t e r p o la t in g , th e pay back p e r io d = 3 .2 y ea rs
Return o f Investm ent:
C a p ita l in v estm en t _ 2 ,0 0 0 ,0 0 0 Annual cash flo w ** 898 ,425 42%
T able A .14 E stim ation o f th e D iscou n ted Cash Flow Assuming a 20% Change in th e Annual Cash Flow s.
Y ear Cash Flow
D iscou n t Rate
10% 30% NPVD iscou n t
Rate (25%) NPV
1 - 400 ,000 1 .000 - 4 0 0 ,0 0 0 - 4 0 0 ,0002 -1 ,6 0 0 ,0 0 0 .909 -1 ,4 5 4 ,0 0 0 -1 ,4 5 4 ,4 0 03 718 ,740 .392 4 2 5 ,4 9 4 .640 459 ,9944 . 718 ,740 .443 319,839 .512 367 ,9955 718 ,740 .3 5 0 251 ,559 .410 294 ,6836 718 ,740 .269 193 ,341 .328 235 ,7477 718 ,740 .2 0 7 148 ,779 .262 188,3108 718 ,740 .159 114 ,280 .210 150,9359 818 ,740 .123 88 ,405 .168 120,748
.094 76 ,9 6 2 .134 109,711
- 235 ,7 4 0 - 7 4 ,1 2 3
By in t e r p o la t in g . D iscou n ted Cash Flow = 26.2%Change in th e p r o f i t a b i l i t y = 26.8%
T ab le A .15 E s t im a t io n o f th e N et P r e s e n t V alue
D iscou n t Rate
Year Cash Flow 10%* 25% NPV
0 - 4 0 0 ,000 1 .000 - 4 0 0 ,0001 -1 ,6 0 0 ,0 0 0 .909 -1 ,4 5 4 ,4 0 02 718 ,740 .640 459 ,9933 7 1 8 ,7 4 0 .512 367 ,9954 7 1 8 ,740 .4 1 0 294 ,6835 7 1 8 ,7 4 0 .328 235 ,7466 7 1 8 ,740 .262 188 ,3107 7 1 8 ,740 .210 150,9358 7 1 8 ,740 .168 120 ,7489 818 ,740 .134 109,711
$ 73 ,7 2 2
N et p r e se n t v a lu e @ 25% = $73 ,722
*The r a te o f 10% i s c o n s id e r in g a f in a n c ia l loan from a bank.
APPENDIX B
STATISTICAL CALCULATIONS FOR THE ALAMOS MINING
DISTRICT EXPLORATION PROGRAM, 1973-75
141
' 0 7 / 1 4 / 7 5 PAGE 1
VCGELBACK COMPUTING CENTER NORTHWESTERN UNIVERSITY
S P S S ---- STATISTICAL PACKAGE FOR THE SOCIAL SCIENCES
VERSION 5.8 — AUGUST 30/ 1974
•i
RUN NAME VARIABLE LIST INPUT FORMAT
REGRESSION ALAMOS MINING DISTRICTMINES/X/Y/XZ/Y2/XY/GR/ANT,VOLC/MET/NEST/NWEST/EWEST>AGE (8X,F2.0/2F5.0 /5X/3F3.0 , IX,4F1.0,2X/3F1.0,4X/FI.0)
ACCORDING TO YOUR INPUT FORMAT/ VARIABLES ARE TO BE READ AS FOLLOWS
VARIABLE format RECORD
MINES F 2. 0 1X f 5. 0 1Y F 5. 0 1X2 F 5# 0 1Y2 F 5. 0 1XY ? 5. 0 1GR F 1. o 1ANT F 1. 0 1VOLC F 1. 0 1MET F 1. 0 1NEST F 1. 0 1INWEST F 1. 0 1EwEST F 1. 0 1AGE F 1. 0 1
THE INPUT FORMAT PROVIDES FOR 14 VARIABLES.IT PROVIDES FOR 1 RECORDS (♦CARDS*) PER CASE.
COLUMNS
9- 10 ^11- 1516- 20 26- 3031- 3536- 4042- 4243- 4344- 4 445- .4548- 4044- 495C- 5055- 55
14 WILL BE READA MAXIMUM OF 55 ♦COLUMNS* ARE USED ON A RECORD.
# OF CASES 140REGRESSION VARIA3LES-MINES TO AGE/
REGRESSION-MINES WITH X( 1)Y(1)X2(1)Y2( 1>XY(1)GRCl)ANT(1)VOLC(1) METtDNESTCl )NWEST(1)EWESTC1)AGEC D/RESIDUALS
OPTION 12READ INPUT DATA
050700 CM NEEDED FOR REGRESSION
142
RECESSION ALAMOS MINING DISTRICT 07/14/75 PAGE 2
.FILE NONAME (CREATION DATE • 07/14/75 )+ * + + + + + + * » * + + + * + + + + + + + + M U L T I P L E R E C» R E S S I 0 N * * * * * * * * * * * * * * * * * * * * * * *
ChPENDENT VARIABLE.. MINES
V/.RIABLE(S) ENTERED ON STEP NUMBER 1 . . ANT
MULTIPLE R .51781 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SCUARE .26813 REGRESSION 1. 24.07616 24-07616 50. 55807 .000STD DEVIATION .69008 RESIDUAL 138. 65.71670 .47621
i # i r t v »ni re r»i tia c c m 11 T T Hki ____________________ — VARIABLES fJOT IN THE ECUAT ION
VARIABLE B STD ERROR B . F BETA VARIABLE PARTIAL TOLERANCE F
SIGNIFICANCE ELASTICITY SIGNIFICANCE
ANT 1.5412262 .21675601 50.556067 .5178127 X -.21891 ♦99210 6.8953057.000 .39427 .010
(CONSTANT) .13604651 .6075d002E-01 9.3763994 Y .14894 .97948 3.1061235• 003 .060
X2 -.22070 .99942 7.0149660.009
Y2 ♦14728 •99367 3.0375256.084
XY -.09046 .97302 1.1304162.293GR .23234 .98101 7.6175227
.006VCLC -.00246 .99334 .6 3169900E-03
.977MET .32923 .97532 16.655409
.000NEST .18162 .95408 4.6733687
• .032NWEST -.29293 .90734 12.856932
.000EWEST -.14448 .99654 2.92093G7
.090AGE .21658 • .98504 6.8741638
143
REGRESSION ALAMOS M IN ING D IS T R IC T 0 7 / 1 4 / 7 5 PAGE 3
FILE NONAME (CREATION DATE • 07/14/75 )« . » + * + + * * * * * * * + + + + + + * + * + M U L T I P L E R E G R E S S I O N * * * * * * * * * * * * * * * * * * * * * * *Cc?EKOENT VARIABLE..
VARIABLE IS) ENTERED
MINES
ON STEP NUMBER 2 . . MET - ;
.VJL7IPLE R .58945 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SCOARE .34746 REGRESSION 2. 31.19952 15.59976 36.47457 .000STB DEVIATION .65398 RESIDUAL 137. 58.59334 •42769
VARIABLES IN THE EQUATION —— —— — —— ——— VARIABLES NOT IN THE EQUATION
VARIABLE B STD ERROR B F BETA VARIABLE PARTIAL ' TOLERANCE F
SIGNIFICANCE ELASTICITY SIGNIFICANCE
ANT 1.4078641 .20800010 45.613594 .4730 >64 X -.09Q77 ' .80878 1.12971480 .36015 .290
MET .61641932 .15104206 16.655439 .2351993 r .08745 .93751 1.0481441.000 .32971 .303
(CONSTANT) •95255996E-01 •61727810E-01 2.3613482 X2 -.11059 .85774 1.6639570.125 ,0 .197
, Y2 •09390 .96055 1.2097702.273
XY -.00308 ♦91107 .5868664 5E.925
GR .15491 .90461 3.3438449.070
VOLC -.05420 .97257 .40075461. 528
NEST .16065 *94585 3.6030933.060
NVEST -.23629 .85924 8.0422123.005
EVEST -.12239 •98860 2.0680526.153
AGE .13352 .89731 2.4685260.118
144
* * * * * * * * * * * * * * * * * * * * * * * M U L T I P L E R E G R E S S I O N ♦ ♦ * ♦ ♦ * * * ♦ ♦ ♦ * ♦ * ♦ ♦ * * ♦ • * * •DEPENDENT VARIABLE.. MINES
REGRESSION ALAMOS M IN IN G D IS T R IC T 0 7 / 1 4 / 7 5 PACE 4
F IL E NONAME (CREATION DATE • 0 7 / 1 4 / 7 5 )
VARIA3LECS) ENTERED ON STEP NUMBER 3 . . NVEST
MULTIPLE R .61959 R SQUARE .33389 STD DEVIATION .63779
ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCEREGRESSION 3. • 34.47092 11.49031 28.24705 .000RESIDUAL 136. 55.32194 .40678
——— —— — —— — VARIABLES IN THE EQUATION
variable 8 STD ERROR B F
SIGNIFICANCEANT 1.2426877 .21104326 34.670527
•• .000MET •51727797 .15137089 11.691403
.001NVEST -.32110040 .12380623 8.0422123
.005(CONSTANT) .36021128 •11114468 10.503578
.001
1
•
VARIABLES NOT IN THE ECU/ 0 z 1 i !
BETA VARIABLE . PARTIAL TOLERANCE F
ELASTICITY
.4175114 X -.11672 .80167
SIGNIFICANCE
1.8647325.31790
.2394631 Y .07681 .93470. 1 7 4
.80116456.27684
-.2059156 X2 -.13281 .85272.372
2.4236090-.76752 .122*
Y2 .03121 .95660 .89617169
XY -.03144 .90293.345
.13322663
GR .16169 .90453.715
3.6241671
VOLC -.02090 .9*230.059
.56977144E-01
NEST .18822 .93804.603
4.9280633 •
EWEST -.14073 .98508.028 *
. 2.7272339
AGE .14201 .89699.101
2.7733962• 098
145
REGRESSION ALAMOS M IN ING D IS T R IC T 0 7 / 1 4 / 7 5 PAGE 5
FILE NONAMe (CREATION DATE ■ 07/14/75 )♦ ♦ ♦ ♦ ♦ ♦ * * * * * * * * * * * * * * * * * M U L T I P L E R 6 G R E S S I O N * * * * * * * * * * * * * * * * * * * * * * *
DEPENDENT VARIABLE.. MINES
VAR I ABLE(S) ENTERED ON STEP NUMBER 4 . . NEST •
MULTIPLE R .63646 ANALYSIS OF VARIANCE DF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SCUARE .40572 REGRESSION 4. 36.43072 9.10768 23. 04137 .COOSTD DEVIATION .62871 „• RESIDUAL 135. 53.36214 .39528
■ UA Q T i m CC MflT TM T M P POM ATIQNV A K A A O L C J l i U l * i i i n c c u u
VARIABLE a STD ERROR B F BETA variable PARTIAL TOLERANCE F
SIGNIFICANCE ELASTICITY SIGNIFICANCE
ANT 1.1402874 .21306484 28.642115 .33:,1075 . X -.12119 •80155 1.99724400 .29170 .160
MET .46030677 .15015104 10.232476 .2222233 Y .05209 .91666 .36461155. 0 0 2 .25691 .547
NwEST . -.37590216 .12255056 9.4084702 -.2204615 X2 -.12793 •85145 2.2293931.003 -.62174 .133
NEST .25611829 .11502296 4.9580633 .1525367 Y2 .06275 •94588 .52967736.023 .54202 .463
(CONSTANT) •22455537 .12536107 3.2086531 XY -.04294 .90003 .24756793.075 .620
GR .14709 .89637 2.9634474\ • Oo 71 VOLC -.04022 .94313 .21709327
. 0 4 2
EVEST -.11303 .96641 1.8930724.171
. AGE .13005 .89154 2.3053949. • 131
146
FILE NONAME (CREATION DATE * 07/14/75 )
* * * * * * * * * * * * * * * * * * * * * * * M U L T I P L E R E G R E S S I O N * * * * * * * * * * * * * * * * * * * * * * *DEPENDENT VARIABLE.. MINES
VARIABLECS) ENTERED ON STEP NUMBER 5 . . GR
REGRESSION ALAMOS MIN ING D IS T R IC T 0 7 / 1 4 / 7 5 PAGE 6
MULTIPLE R .64693 ANALYSIS OF VARIANCE DF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SQUARE .41653 REGRESSION 5. 37.53530 7.51706 19.29388 .000STD DEVIATION .62419
C'RESIDUAL 134. 52.20755 .38961 •
VARIABLES IN THE EQUATION---------------------------------- --------------- VARIABLES NOT IN THE EQUATION------------------
VARIABLE a STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F
SIGNIFICANCE ELASTICITY SIGNIFICANCEANT 1.1134199 .21210712 27.555448 .3740807 X -.10238 .78528 1.4086984
.000 .23483 .237MET .41003730 .15455862 7.0361763 .1897122 Y .02204 .87655 .64653452E-G1
.009 .21932 .SCOHUE ST -.37603244 •12166900 9.5519215 -•2205379 X2 -.10502 .82558 1.4832o93
.002 -.82202 .225NEST •23736042 .11471421 4.2813640 .1413651 * Y2 .03887 .91887 .20120916
• 040 .50232 .654GR .19472063 .11311322 2.9634474 .1197700 XY -.06457 - .88287 .55661245
.087 •37133 .457(CONSTANT) .13644059 .13457389 1.0279348 VOLC -.05560 .93401 .41241125
.312 .522EWEST -.12537 .96436 2.1239200
.147AGE -.02185 .11065 • 63512046E-01
.801
147
FILE NONAME (CREATION DATE - 07/14/75 )
REGRESSION ALAMOS M IN IN G D IS T R IC T 0 7 / 1 4 / 7 5 PAGE 7
* * * * * * * * * * * * * * * * * * * * * * ♦ M U L T I P L E R E G R E S S I 0 N ♦ ♦ * * * * * * * * * * * * * * * * * * * * *
DEPENDENT VARIABLE.. MINES •
VARIA9L £(S) ENTERED ON STEP NUMBER 6 . . EVEST
MULTIPLE R .65400 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SQUARE .42772 REGRESSION 6. 38.40592 6.40099 16. 56707 .000STD DEVIATION .62159 RESIDUAL 133. 51.38694 .38637
--------------- —--------------- VARIABLES IN THE EQUATION —————— ————— VARIABLES NOT IN THE EQUATION -----------------
variable B STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F
SIGNIFICANCE ELASTICITY SIGNIFICANCEANT 1.1037399 .21132649 27.281297 .3708452 X -.09033 .77649 1.0858013
0 .28236 .299MET •38905375 •15459648 6.3339724 .1800037 Y .03159 ^ .87182 .13183582
.013 .20810 .717NVEST -.38443381 .12129900 10.044503 - . 2 2 6 4 6 7 2 X2 -.09738 .82166 1.2636676
. 0 0 2 -.34039 .263NEST .21367395 .11538653 3.4292003 .1272631 . Y2 .04917 .91330 .31984790
.066 .45219 .573GR .20129039 .11273197 3.1882367 .1238103 XY -.04858 .86700 .31221440
.076 .38336 .577EVEST -.17527075 .12026531 2.1239200 -.0973232 VOLC -.04867 .93075 .313362C6
.147 -.15439 .577(CONSTANT) •20540732 .14212299 2.088S301 AGE -.00982 .10961 •12723C42E-01
.151 .910
148
REGRESSION ALAMOS M IN ING D IS T R IC T 0 7 / 1 4 / 7 5 PACE 8
FILE NONAME (CREATION DATE - 07/14/75 )* * * * * ♦ * ♦ * * * * ♦ * ♦ * ♦ * * ♦ * ♦ ♦ M U L T I P L E R E G R E S S I O N A * * * * * * * * * . * * * * * * * * * * * * *DEPENDENT VARIABLE.. MINES
VARIA3LECS) ENTERED ON STEP NUMBER 7 . . X2
MULTIPLE R .65614 ANALYSIS OF VARIANCE DF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SQUARE .43314 REGRESSION 7. 33.69319 5.55617 14.40902 .000STD DEVIATION •62G97 r;* RESIDUAL 132. 50.89966 .38560
--------------- variables in the equation ------- ------- VARIABLES NOT IN THE EQUATION -----------------
VARIABLE 3 STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F
ANT ' 1.1247436 .21193860
. SIGNIFICANCE
28.163522
ELASTICITY
•3776852 X .01950 .04090
significance’
•49S2176GE-Q1
MET .32907200 .16339161• QUO
A.0562230.28773
.1522519 Y .04392 .85901.£24
.25320594
NVEST -.39407626 .12148216.04b
10.522903.17602
-.2311204 Y2 .05921 .90463.616
.46069257
NEST .21207361 .11523107.001
3.3643696-.36147
•1263080 • XY .02235 .47935• 493
.65445164E-01
GR •17349663 .11443116.068
2.4331656.44302
.1097903 VOLC -.05650 .92537.793
.41954220
EWEST -.16593930 .12043267.121
1.3965084• 34G39
-.0921420 AGE -.01984 .10849' .510
• 5156G1C0E-G1
X2
(CONSTANT)
-.10469930E-02
.30785102
.93136093E-03
.16571261
.1711.2636676
.2633.3295544
.070
—.14664 -.0312680
-.24714o
. .621
149
* * + + * * + ♦ * + + + * + + + + + + + + + + M U L T I P L E R E G R E S S I O N * * * * * * * * * * * * * * * * * * * * * * *
DEPENDENT VARIABLE.. MINES
VARIA3LECS) ENTERED ON STEP NUMBER 8 . . Y2
REGRESSION ALAMOS M IN IN G D IS T R IC T 0 7 / 1 4 / 7 5 ' PAGE 9
F IL E NONAME (CREATION DATE • 0 7 / 1 4 / 7 5 )
MULTIPLE R .65964 ANALYSIS OF VARIANCE DF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SQUARE .43513 REGRESSION 8. 39.07164 4.88396 12. 61402 .000STD DEVIATION .62224 C RESIDUAL 131. 50.72121 .33718
_ v A D T A Rf P < U n T rv! r u e c n n—————————— v A K 1 A D L C J i n t n C C U U A I l U n —————— —— V A K A A o L C J n U 1 *VARIABLE B STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F
SIGNIFICANCE ELASTICITY SIGNIFICANCE
ANT 1,1263096 .21238525 26.123335 .3764113 X .02124 •04086 •53657471E-010 •26313 • bC9
MET ,31360834 .16530314 3•5992582 .1450974 Y -.05972 .04539 .46526443• .060 • lo774 .496
NVEST -.38871203 .12193716 10.153779 -.2279743* XY -.05471 .12869 .39025958.002 -.54974 .533
NEST .20397740 .11013191 3.0350411 .1214831 VOLC -.04585 .88974 .27390434.031 .43167 . .602
GR .16415923 .11659416 1.9323349 .10:9721 ACE -.01276 •10689 •21177402E-01.162 .31305 .865
EV6ST -.17180203 ; .12093789 • 2.0163616 -.0913971• loO -.15133
X2 — • 11069963E-02 •93774691E-03 1.3985655 -.0860607.239 -.26177
Y2 , 11596793E-02 .17081974E-02 .46069257 .0468703 0 •.496 .14450
(CONSTANT) .28203401 .17328248 2.6490714.106
•
•McnO
FILE NONAME (CREATION DATE ■ 07/14/75 )
A * * * * * * * * * * * * * * * * * * * * * * M U L T I P L E R E G R E S S I O N ♦ * * # ♦ * ♦ * ♦ * * ♦ * * * * * ♦ * ♦ * * *DEPENDENT VARIABLE.. MINES
VARIABLEISI ENTERED ON STEP NUMBER 9 . . Y
REGRESSION ALAMOS M IN IN G D IS T R IC T 0 7 / 1 4 / 7 5 PAGE 1 0
MULTIPLE R •66117 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SQUARE •43716 . REGRESSION 9. . 39.25253 4.36139 11.21839 .000STD DEVIATION .62362 C RESIDUAL 130. 50,54033 .33877
VARIABLES IN THE EQUATION-------------------------------- - --------------- VARIABLES NOT IN THE EQUATION
variable 6 STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F
SIGNIFICANCE ELASTICITY SIGNIFICANCE
ANT 1.1577860 .21776558 28.266896 .3089865 X .01619 •04056 •33817644E-01.000 .29613 .854
MET .32567976 •16659428 3.8222009 .1505025 XY -.03501 .11076 .15827111.053 .17420 .691
N'.'EST -.38673335 .12226958 10.006906 -.2263435 VOLC -.04687 •68953 .28402105.002 -.84553 • 595
NEST .21561672 .11761409 3.3603271 .1284151 AGE -.01428 •10682 .263167155-01.069 .45631 .871
GR .18183333 .11966755 2.3093397 .1113739.131 .34685
EWEST -.17324346 • .12125400 2.0413692 -.0961975.155 -.15310 o
X2 -.10344128E-02 •94600704E-03 1.19563o2 -.0602915.276 -.24417
Y2 •61023166E-02 .74463123E-02 .67170432 .2465575.414 .75044
Y -.53738499E-01 .86113829E-01 .46526443 -.2106653.496 -1.05133
(CONSTANT) .38720101 .23221009 2.7804226
V IM
FILE NONAME ' (CREATION DATE - 07/14/75 )
REGRESSION ALAMOS M IN IN G D IS T R IC T 0 7 / 1 4 / 7 5 PAGE 11
+ + ++ + + * * * * * * + * + + + + ♦ ♦ ♦ * * M U L T I P L E R E G R E S S I O N + * * * * * * * # * * * + + * + * » * * # # *
DEPENDENT VARIABLE.. MINES
VARIABLE(S) ENTERED ON STEf NUMBER 10.. VOLC
MULTIPLE R .66210R SQUARE *43333STD DEVIATION .62524 ^
ANALYSIS OF VARIANCE OFREGRESSION 10.RESIDUAL 129.
SUM OF SQUARES 39.36356 50.42930
MEAN SQUARE F SIGNIFICANCE3.93636 10.06934 .000
.39092
VARIABLES IN THE EQUATION--------------- :------------------ --------------- VARIABLES NOT IN THE EQUATION
VARIABLE B STD ERROR B F BETA VARIABLE PARTIAL TOLERANCE F
SIGNIFICANCE ELASTICITY SIGNIFICANCE
ANT 1.1663297 .21895542 28.374700 .3918570 X .02828 •03823 .102467900 .29036 .749
MET •33004648 .16864896 4.0177742 .1564042 XY -.02924 .10892 .10953082.047 .10092 .741
NWEST -.37061595 .12356187 9.3892056 -.2220531 AGE -.00147 .09877 .27651422E-03.003 -.02767 .987
NEST •22300517 .11076097 3.529055b .1325631• Ot>3 .47211
CR .13950265 .12086705 2.4581859 .1165605.119 .36133
EWEST -.16303097. .12197336 1.8991027 -.0933354.171 -.14054
X2 -.10625892E-02 •95009510E-03 1.2508251 -.0824706.265 -.25032 •
Y2 •59799530E-02 •74704609E-02 .64076709 • 2t-16918 ».425 .74513
Y -•59453909E-01 •86362384E-01 .47392715 -.2132311.492 -1.06464
VOLC -.79226609E-01 .14066057 .26402105 -.0372839.595 -.04422
(CONSTANT) .39255898 .23306913 2.8368758• 095 . . . - '
152
r —•*
FILE NCNAHE (CREATION DATE - 07/14/75 )* * * * * * * * * * * * * * * * * * * * * * * M U L T I P L E R E G R E S S I O N * * * * * * * * * * * * * * * * * * * * * * *DEPENDENT VARIABLE.. MINES
VAR I ABLE(S) ENTERED ON STEP NUMBER 11.. XT
RE5RESSI0N ALAMOS M IN IN G D IS T R IC T 0 7 / 1 4 / 7 5 PAGE 12
MULTIPLE R .66247 ANALYSIS OF VARIANCE OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SQUARE •43636 REGRESSION 11. 39.40668 3.53243 9.10072 .000STD DEVIATION .62741 RESIDUAL 128. 50.38618 .39364
•
—-------------—————------- — VARIABLES IN THE EQUATION------------ ————------------- — —————————— VARIABLES NOT IN THE EQUATION
VARIABLE 8 STD ERROR 8 F BETA VARIABLE PARTIAL TOLERANCE F
SIGNIFICANCE ELASTICITY SIGNIFICANCE
ANT 1.1804315 •22380835 27.818200 .3965949 X .03723 .03562 •17629295.000 .30197 .675
MET .31094384 .18799917 2.7356847 .1438669 AGE .00030 ° . 09841 •11600343E-04.101 .16632 .997
NVEST -.36040767 .12410871 9.3949496 -.2231040 .
.003 -.63159NEST .22076035 .11938785 3.4191797 .1314735
.067 .46719 •GR .19983061 .12527424 2.5457617 .1229438
.113 .38117EVEST —.16329060 .12325222 1.7552253 -.0906709 •
.100 -.14430X2 -.54221572E-C3 •18357709E-02 • 8 6953834E-01 — . 04 20a 7 0
• 7o9 -.12799Y2 .603 35032E-02 •74981247E-02 .64749106 .2433561
.423 .75100Y -.47760166E-01 •93587640E-01 .26043103 -.1712915
.611 -.55524VOLC -.72810059E-01 .15043089 .23426570 -.0342642
.629 -.34064XY -.16103594E-02 •46671319E-02 .10953662 -.0653975
.741 -.21634(CONSTANT) .35249195 .26335291 1.7915220
.163
153
FILE . NONAME (CREATION DATE • 07/14/75 )« ♦ « * * * * * * * * . * * * * * * * * * * * M U L T I P L E R E G R E S S I ON * • ♦ * * * ♦ * * * * * * * * * * ♦ * ♦ * * *DEPENDENT VARIABLE.. MINES
VAR IA3L E(S) ENTERED ON STEP NUMBER 12.. X
REGRESSION ALAMOS M IN IN G D IS T R IC T __ 0 7 / 1 4 / 7 5 PAGE 1 3
MULTIPLE R .66305 ANALYSIS OF VARIANCE . OF SUM OF SQUARES MEAN SQUARE F SIGNIFICANCER SQUARE .43964 1 REGRESSION 12. 39.47652 3.26971 8.30333 .000STD DEVIATION .62944 RESIDUAL 127. 50.31634 .39619 .
VARIABLES IN THE EQUATION---------------------------------- --------------- VARIABLES NOT IN THE EQUATION
VARIABLE a STD ERROR B F SETA VARIABLE PARTIALl TOLERANCE F
SIGNIFICANCE. ELASTICITY SIGNIFICANCE
ANT 1.1582768 .23064865 25.218709 .3891514 ' " AGE -.00081 .09832 • 81968237E-04• COO .29630 - .993
MET .33054172 .19429391 2.8942373 .1529319.091 .17680
NW5ST -.37401406 .12543774 8.8903612 -.2193541.003 -.61761
NEST • .20857116 .12324107 2.8641251 .1242190.093 .44139
GR .19781684 .12577536 2.4736338 .1216744.116 .37723
EWEST -.16997156 .12467032 1.8587731 -.0943007.175 -.15021
X2 -.217546702-02 .430512462-02 .25534865 —.1626606.614 -.51351
Y2 •57662480E-02 •75492496E-02 .58341698 .2330545.446 .71050 >
Y -.405135852-01 •95463533E-01 .18010524 — .1453017.672 -.72543
VOLC -.86677075E-01 .15448879 .31478538 -.0407900-.576 -.04538
XY -.216585902-02 • 50586683E-02 .18331076 -.0392739• 6o9 -.29033
X .293585262-01 •69922476E-01 * .17629295 .1477761.675 . •71669
(CONSTANT) .25153076 .35724419 .49573758.433
f-LEVEL OR TOLERANCE-LEVEL INSUFFICIENT FOR FURTHER COMPUTATION.
154
FILE NONAME (CREATION DATE » 07/14/75 )* * * * * * * * * * * * * * * * * * * * * * * M U L T I P L E R E G R E S S I O N * * * * * * * * * * * * * * * * * * * * * * * .
DEPENDENT VARIABLE.. MINES c*
DEGRESSION ALAMOS M IN IN G D IS T R IC T 0 7 / 1 4 / 7 5 PAGE 14
SUMMARY T A B L ESTEP VARIABLE
ENTERED REMOVEDF TO
ENTER OR REMOVESIGNIFICANCE MULTIPLE R R SQUARE R SQUARE
CHANGESIMPLE R OVERALL F SIGNIFICANCE
1 ANT 50.55307 .000 .51781 .26813 .26613 .51781 50.55807 .0002 MET 16.65549 .000 .58946 .34746 .07933 .35951 36.47457 .0003 N WEST f . 8.04221 .005 .61959 .38389 .03643 -.39633 28.24705 .0004 NEST 4.95606 .02d • 6.16 9 6 .40572 .02183 .26272 23.04137 .0005 GR 2.96345 ■ .087 ' .64693 .41853 .01236 .26823 19.29338 .0006 EWEST 2.12392 .147 •65400 .42/72 .00914 -.15356 16.56707 .0007 X2 1.26367 .263 .65314 .43314 .00543 -•17o2S 14.40902 .0003 Y 2 .46089 • 493 .65964 .43513 .00199 ♦ 16630 12.61402 .0009 Y .46526 .496 .66117 .43715 .00201 .20023 •11.21339 .000
10 VCLC .26402 .595 .66210 .43633 .00124 .03854 10.06934 .00011 XY .10954 .741 .66247 •43886 .00046 .00371 9.10072 .00012 X .17629 .675 .66305 .43964 .00078 -'.14050 8.30333 .000
155
FILE NGNAM5 (CREATION DATE • 07/14/7S )
REGRESSION ALAMOS M IN IN G D IS T R IC T
* * * * * + + + * * * * + * * * * * * * * * M U L T I P L E
iSERVATION Y VALUE Y ESTIMATE RESIDUAL
1. 0 . 7635772E-01 -.76357726-012. 0 • 509 7702E-01 -.50977025-013. 0 .37120022-01 -.37120826-014. 1.000000 .40dd272 .59117235. 0 .3700430 -.37004306. 0 • 7535606 -.75053067. 1.000000 .86206642-01 .91369348. 0 ♦6692338 -.66923339. . 1.000000 .7245006 .2754194
10. 0 1.155474 -1.16547411. 0 , .66264666-01
c -.1350937-.86259636-01
12. 0 .139093713. 0 -.1551073 .155107814. 0 -.1595894 .159539415. 0 -.1525384 .152539416. 0 -.1061097 .106109717. 0 .6330905 -.633090618. . 0 .6747391 -.674739119. 0 .7279200 -.727920020. 1.000000 .7926334 . .207366621. 1.000000 / .6351702 .314329822. 0 .72U7259E-01 -.72872596-0123. 0 -.1152739 .115279924. 0 -.1497716 .149771625. 0 .2615015 -.261501526. 0 .1912420 -.191242027. 3.000000 .9237470 2.07625223. 3.000000 .4192447 2.50075529. 2.000000 1.103922 .899077530. 0 .2610974 -.261097431. 0 -.55422156-01 .55422156-0132. 0 .1212707 -.121270733. 0 •7663011 - . 7b6o31134. . 0 .7500670 -.758067035. 1.000000 .9693502 .30641706-0136. 0 .1443761 -.144376137. , 0 .20344426-01 -.2034442E-0138. 0 .2102313 -.218231339. 0 .3566303 -.3506303•tu. 0 .2535691 -.253569141. 0 .35435806-01 -.35485002-0142. 0 •2100123 -.210012843. 0 .2741783 » -.274173344. 0 .54627956-01 -.54627956-0145. 0 .55131302-01 -.55101306-0146. 0 •6498524 -.649852447. 0 —.1653231 .153:30148. 0 .9524062 -.952436249. 0 .7553049 -.7553049
0 7 / 1 4 / 7 5 PAGE 15
E G R E S S I . O N 4i *4r . * * * * * * * * * * * * * * * * ♦ * ♦ *
-2SD 0.0 *2S0
McnOx
70 7
0
FILE NONAME (CREATION DATE ■ 07/14/75 ) *# + * + * + + + % + * + + + + * + + + + + ♦ * M U L T I P L E
REGRESSION ALAMOS M IN IN G D IS T R IC T
OBSERVATION Y VALUE Y ESTIMATE RESIDUAL
50. 1.00000051. 052. 1.00000053. 054. 055. 2.00000056. 1.00000057. 058. 059. 1.00000060. 061. 062. 063. 064# 065. 066. 2.0000006 7. •1.00000063. •4.00000069. 070. 071. 072. 073. 074. 075. 076. 2.00000077. 5.00000076. 3.00000079. 0SO. 1.00000081. 082. 083. 034. 06 5. 08 6. 2.00000087. 088. • 1.00000089. 090. 091. 092. 093. 094. 095. 096. ’ 097. 098. 0
.6157039
.337A633E-01
.9156653 -.1054336
.2554354
.6:23656 • .6422856
.1197525
.1527375
.7412405 v .16668458-01
C .762V953E-01 .2070552 .1104032E-01
' .2523701.50702 87E-01 •6303679 1.721254 1.833750 .3442626
/; .1941242-.1655963
.2433192E-02 -.1965476
.2404412 - . 1332915
2.102913 2.120039 2.143692 .3260450 .3777633 .4938758 .2011966
-.1239525 .26336435-01 .13226396-01 1. 751756 1.556376 1.249213 .1289563 .5525228
-.1028507 .603 4707E-01 .27506145-01 .56976975-02
-.45732475-02 1.154955 1.943076
-.1469370
.3842961 -.38748335-01
.84334725-01
.1054336 -.2554354
1.367634 .3577144
-.1197525 -.1527375
.2537595 -.16838455-01 -.76259535-01 -.2078552 - . 1 1G4032E-01 -.2523781 -.50782675-01
1.369632 -.7212542
2.161250 -.3442826 -.1941242
.1655963 -.24331925-02
.1965476 -.2404412
.1332915 -.1029178
2.379961 .3513082
-.3260450 .6222367
-.4938758 -.2611966
.1239925 -.26336485-01 -.18226395-01
.2482435 -1.556376 -.2492132 -.1289563 -.5525228
.1028507 -.60647075-01 -.27506145-01 -.65976975-02
.45782475-02 -1.154955
° -1.943076.1469370
0 7 / 1 4 / 7 5 PAGE 16
G R E $ $ I 0 N f t * * * * * * * * * * * * * * * * * * * * *
2SD
R
0.0
RIII
+2SD
R
R
R
R
157
FILE NONANE (CREATION DATE ■ 07/1A/75 )* + + + + + + + + + + + + + M U L T I P L E
REGRESSION ALAMOS M IN IN G D IS T R IC T
OBSERVATION Y VALUE Y ESTIMATE RESIDUAL
99. 0 .2674593 -.2674598ICO. 0 -.52942036-01 .52942082-01101. 0 -.1213423 .1213428102. 0 -.3383536 .3303536103. 0 . 4662279E-02 -.46022795-02104. 0 -.19292025-01 .19292025-01105. 0 -.31733025-01 .31733322-011Gb. 1.000000 1.412971 -.4129706107. 0 .48756095-01 -.40 75b09£-01108. 0 .1979526 -.1979526109. 0 . .2316403 -.2316408110. 0 - .2444875 -.2444075111. 0 .2654278 -.2604278112. 0 -.1933910 .1933910113. 0 -.224 92512-01 .22492515-01114. 0 - . 5316133E-01 .53161335-01115. 0 • J 4 C 3 (' 2 2 —. 1406022116. •0 .44624272-01 -.44824272-01117. 0 .12917372-01 -.12917375-01118. 0 -.2165942 .2105942119. 0 /" .21499272-01 -.21499276-01120. 0 .32130146-01 -.32100145-01121. 0 • 32662 b2E-01 -.32662622-01122. c -.16706305-01 •10700305—01123. 0 -.2625394 .2625394124. 0 .33110 64E—01 -.83110646-01125. 0 .2641620 -.2641620126. 0 .9 34 76 042-01 -.93473046-01127. 1.000000 .4737636 .5262164120. 0 .1175935 .-,1175935129. 0 .3123928 -.3123928130. 0 -.2166491 .2165491131. 0 -.2029248 •2029248132. 0 -.47390525-01 .47390522-01133. 0 -.2934661 .2934661134. 0 -.1203668 ,1203668135. c .53510692-01 -.58510695-01136. 0 .51103615-01 t . 51103312-01137. 0 -.1533417 .1533417133. 0 -.99034C3E-01 .99084035-01139. 0 -.1042674 .1042674140. 0 -.4395563 .4395533
NOTE - <*> INDICATES ESTIMATE R INDICATES POINT OUT
CALCULATED WITH OF RANGE Of PLOT
MEANS SU3ST1TUT50
140.8. OR 5.71 PERCENT OF THE TOTA
NUM5ER OF CASES PLOTTED NUMBER OF 2 S.D. OUTLIERS
0 7 / 1 4 / 7 5 PAGE 17
R E G R E S S I O N + * * + * + + ++ + * + + * + $ * + * + + + *
-2 SO 0.0II •II
+ 2SD
I.I.I
, I I I I I II.I •I
» I• I I
• I.1• I I.I
. IIIIIIIII .II
• I• I
IIII
158
TREND SURFACE ALAMOS MINING DISTRICT
COEFFICIENTS OF FIRST-DEGREE EQUATION
Z - •3 9 3 2 2 + - . 0 4 9 8 9 X + . 0 9 1 3 4 Y
COEFFICIENTS OF SECOND-DEGREE EQUATION
Z * - . 8 1 6 7 7 +' . 1 2 9 1 2 X + . 4 1 6 6 2 Y ♦ - . 0 0 9 2 7 X2 + - . 0 0 7 2 6 XY f 02 46 2 Y2
COEFFICIENTS OF THIRO- DEGREE EQUATION
Z • . . 6 3 8 0 7 +- . 0 0 0 2 0 X3 +
- . 0 6 325 X + - . 0 0 1 9 9 X2Y ♦
- . 7 0 7 0 2 Y + - . 0 0 0 0 2 XY2 ♦
. 0 0 6 1 6 X2 + - . 0 1 3 6 9 Y3
• 0 2 2 8 0 XY ♦ 20153 Y2 +
ERROR MEASURES-
SURFACE FIRST-DEGREE SECOND-DEGREE THIRD-DEGREE FOURTH-DEGREE FIFTH-DEGREE SISTH-DEGREE
STANDARD DEVIATION . 7 9 . 7 6 . 7 1 0 . 0 0 0 . 0 0 C.O
VARIATION EXPLAINED BY SURFACE . 1 5 2 9 9 1 0 8 E + 0 2 .2 3 2 7 2 6 9 6 E + 0 2 .3 2 3 4 3 9 0 4 E + 0 2 0 .
•0 . 0 .
VARIATION NOT EXPLAINEDBY SURFACE .8 7636 6 0 7 E + 0 2 . 7 9 6 6 3 0 1 8 E + 0 2 .7 0 5 9 1 8 1 0 E + 0 2 0 . 0 . 0 .
TOTAL VARIATION .1 0 2 9 3 5 7 1 E + 0 3 . 1 0 2 9 3 5 7 1 E + 0 3 . 1 0 2 9 3 5 7 1 E + 0 3 0 . 0 . 0 .
COEFFICIENT OF DETERMINATION .1 4 8 6 2 7 7 9 . 2 2 6 0 8 9 6 2 . 3 1 4 2 1 4 6 0 0 . 0 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0
COEFFICIENT OF CORRELATION . 3 8 5 5 2 2 7 5 . 4 7 5 4 8 8 8 2 . 5 6 0 5 4 8 4 8 0 . 0 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0
159
TREND SURFACE ALAMOS
X-COORD Y-COORD Z-VALUE IST-SURF: 1ST-RESID
SURFACE ALAMOS MINING DISTRICT1 . 0 0 0 1 . 0 0 0 0 , 0 0 0 . 4 3 5 - . 4 3 51 . 0 0 0 2 . 0 0 0 0 . 0 0 0 . 5 2 6 - . 5 2 61 . 0 0 0 3 . 0 0 0 1 . 0 0 0 . 6 1 7 . 3 8 31 . 0 0 0 4 . 0 0 0 1 . 0 0 0 . 7 0 9 . .2 9 11 . 0 0 0 5 . 0 0 0 1 . 0 0 0 • 800 . 2 0 01 . 0 0 0 6 . 0 0 0 1 . 0 0 0 • 091 . 1 0 91 . 0 0 0 7 . 0 0 0 1 . 0 0 0 .9 8 3 . 0 1 71 .0 0 0 8 . 0 0 0 1 . 0 0 0 1 . 0 7 4 - . 0 7 41 . 0 0 0 . 9 . 0 0 0 1 . 0 0 0 1 . 1 6 5 - . 1 6 51 . 0 0 0 1 0 . 0 0 0 1 . 0 0 0 1 . 2 5 7 - . 2 5 72 . 0 0 0 1 . 0 0 0 0 . 0 0 0 .3 8 5 - . 3 8 52 . 0 0 0 2 . 0 0 0 0 . 0 0 0 ' . 4 7 6 - . 4 7 62 . 0 0 0 3 . 0 0 0 0 . 0 0 0 .5 6 7 - . 5 6 72 . 0 0 0 4 . 0 0 0 0 . 0 0 0 . 6 5 9 - . 6 5 92 . 0 0 0 5 . 0 0 0 0 . 0 0 0 . 7 5 0 - . 7 5 02 . 0 0 0 6 . 0 0 0 0 . 0 0 0 . .8 4 1 - .8412 . 0 0 0 7 . 0 0 0 1 . 0 0 0 .9 3 3 . 0 6 72 . 0 0 0 8 . 0 0 0 1 . 0 0 0 1 . 0 2 4 - . 0 2 42 . 0 0 0 9 . 0 0 0 1 . 00 0 1 . 1 1 6 - . 1 1 62 . 0 0 0 1 0 . 0 0 0 1 . 0 0 0 1 . 2 0 7 - . 2 0 73 . 0 0 0 1 . 0 0 0 1 . 0 0 0 .3 3 5 .6 6 53 . 0 0 0 2 . 0 0 0 0 . 0 0 0 .4 2 6 — . 4 2 63 . 0 0 0 3 . 0 0 0 0 . 0 0 0 .518 - . 5 1 83 . 0 0 0 4 . 0 0 0 0 . 0 0 0 .6 0 9 - . 6 0 93 . 0 0 0 5 . 0 0 0 0 . 0 0 0 .7 0 0 ' - . 7 0 03 . 0 0 0 6 , 0 0 0 0 . 0 0 0 ‘ .7 9 2 - . 7 9 23 . 0 0 0 7 . 0 0 0 3 . 0 0 0 . 8 8 3 2 . 1 1 73 . 0 0 0 8 . 0 0 0 3 . 0 0 0 .974 2 . 0 2 63 . 0 0 0 . 9 . 0 0 0 2 . 0 0 0 1 . 0 6 6 . 9 3 43 . 0 0 0 1 0 .0 0 0 0 . 0 0 0 1 . 1 5 7 - 1 . 1 5 74 . 0 0 0 1 . 0 0 0 0 . 0 0 0 . .2 8 5 • - . 2 354 . 0 0 0 2 . 0 0 0 1 . 0 0 0 .3 7 6 .6 2 44 . 0 0 0 3 . 0 0 0 1 .000 .468 . 5 3 2
district
2ND-SURF 2ND-RESI0 3RD-SURF 3RD-RESI0
- . 3 1 4 .3 1 4 . 2 8 2 - . 2 8 2. 0 2 1 - . 0 2 1 . 1 0 5 - . 1 0 5• 308 • 692 • 166 .8 3 4• 545 . 4 5 5 • 384 • 616. 7 3 2 k .2 6 8 .6 7 5 • 325. 8 7 1 . 1 2 9 .9 6 0 • 040. 9 6 0 • 040 1 . 1 5 4 - . 1 5 4
1 . 0 0 0 — . 0 0 0 1 . 1 7 6 - . 1 7 6• 991 . 0 0 9 . 9 4 3 .0 5 7.9 3 3 • 067 .3 7 4 . 6 2 6
- . 2 2 0 . 2 2 0 .2 53 - . 2 5 3.1 0 8 - . 1 0 8 • 092 - . 0 9 2. 3 8 7 - . 3 8 7 .1 7 0 - . 1 7 0. 6 1 7 - . 6 1 7 .4 04 - . 4 0 4. 7 9 7 - . 7 9 7 .7 1 3 - . 7 1 3.9 2 9 , - . 9 2 9 1 . 0 1 4 - 1 . 0 1 4
1 . 0 1 1 - . 0 1 1 ' 1 . 2 2 4 - . 2 2 41 . 0 4 3 - . 0 4 3 1 . 2 6 3 ' - . 2 6 31 . 0 2 7 - . 0 2 7 1 . 0 4 7 - . 0 4 7
.9 6 1 . . 0 3 9 .494 . 5 0 6- . 1 4 5 1 . 1 4 5 .2 3 0 • 770
. 1 7 6 - . 1 7 6 . 0 8 2 - . 0 8 2
.4 4 8 - . 4 4 8 .1 7 2 - . 1 7 2
. 6 7 1 - . 6 7 1 .4 1 9 - . 4 1 9
.8 4 4 - . 8 4 4 .74 0 - . 7 4 0
. 9 6 8 — . 9 6 8 1 . 0 5 4 - 1 . 0 5 41 . 0 4 3 1 . 9 5 7 1 . 2 7 7 1 . 7 2 31 . 0 6 8 1 . 9 3 2 1 . 3 2 8 1 . 6 7 21 . 0 4 4 . 9 5 6 1 . 1 2 4 . 8 7 6
.9 7 1 - . 9 7 1 .5 8 4 - . 5 8 4- . 0 8 8 • 088 . 2 1 1 — . 2 1 1
.2 2 6 . 7 7 4 .0 7 2 . 9 2 8
. 4 9 0 . 5 1 0 , . .1 7 1 . 8 2 9*o\o
4 . 0 0 04 . 0 0 04 . 0 0 04 . 0 0 04 . 0 0 04 . 0 0 04 . 0 0 05 . 0 0 05 . 0 0 05 . 0 0 05 . 0 0 05 . 0 0 05 . 0 0 0 5 . 0 0 05 . 0 0 05 . 0 0 0 5 .0006 . 0 0 0 6 . 0 0 0 6 . 0 0 0 6 . 0 0 0 6 . 0 0 0 6 . 0 0 0 6 . 0 0 0 6 . 0 0 0 6 . 0 0 0 6 . 0 0 07 . 0 0 07 . 0 0 0 7 . 0 0 07 . 0 0 07 . 0 0 07 . 0 0 07 . 0 0 07 . 0 0 0 7 . 0 0 0 7 . 0 0 0 8 . 0 0 0 8 . 0 0 0
4 . 0 0 05 . 0 0 06 . 0 0 07 . 0 0 08 . 0 0 09 . 0 0 0
1 0 . 0 0 01 . 0 0 02 . 0 0 03 . 0 0 04 . 0 0 05 . 0 0 06 . 0 0 07 . 0 0 08 . 0 0 09 . 0 0 0
1 0 . 0 0 01 . 0 0 02 . 0 0 03 . 0 0 04 . 0 0 05 . 0 0 06 . 0 0 07 . 0 0 08 . 0 0 09 . 0 0 0
1 0 . 0 0 01 . 0 0 02 . 0 0 03 . 0 0 04 . 0 0 05 . 0 0 06 . 0 0 07 . 0 0 08 . 0 0 09 . 0 0 0
1 0 . 0 0 01 . 0 0 02 . 0 0 0
1.0001.0001 . 0 0 0 0 . 0 0 01 . 0 0 0 0 . 0 0 0 0 . 0 0 0 0 . 0 0 0 0.000 0 . 0 0 0 0 . 0 0 0 0 . 0 0 01.000 0.000 1 . 0 0 01.0001 . 0 0 0 0 . 0 0 01 . 0 0 0 0 . 0 0 0 0 . 0 0 02 . 0 0 01 . 0 0 02 . 0 0 01 . 0 0 01 . 0 0 0 0 . 0 0 0 0 . 0 0 0 0 . 0 0 0 0 . 0 0 0 0 . 0 0 0 0 . 0 0 02 . 0 0 02 . 0 0 0 4.0C0 0 . 0 0 01 . 0 0 0 0 . 0 0 0 0 . 0 0 0
, 5 5 9. 6 5 0.7 4 2.8 3 3. 9 2 4
1 . 0 1 61 . 1 0 7
. 2 3 5
. 3 2 6
. 4 1 8
.5 0 9
. 6 0 0
. 6 9 2
. 7 8 3
. 8 7 5
. 9 6 61 . 0 5 7
, 1 8 5. 2 7 7.3 6 3. 4 5 9. 5 5 1.6 4 2. 7 3 3. 8 2 5. 9 1 6
1 . 0 0 7• 135 . 2 2 7
. . 3 1 8 . 4 0 9• 501 .5 9 2 . 6 8 3 . 775 . 6 6 6 . 9 5 7 . 0 8 5 . 1 7 7
. 4 4 1 • :l 50 .2 5 8
— . 8 3 3 .0 7 6
- 1 . C 1 6- 1 . 1 0 7
- . 2 3 5- . 3 2 6— .418 - . 5 0 9— .600
.308- . 7 8 3
.1 2 5
.0 3 4— .0 5 7 - . 1 8 5
.7 2 3— .3 68 - . 4 5 9 1 .4 4 9
.3 58 1 . 2 6 7
. 175 .084
- 1 . 0 0 7 - . 1 3 5 - . 2 2 7
. - . 3 1 8 - . 4 0 9 - . 5 0 1 1 . 4 0 8 1 . 3 1 7 3 . 2 2 5— . 8 6 6
. 0 4 3— .085 - . 1 7 7
• 706 • 294 . 4 2 7 . 5 7 3. 8 7 2 . 1 2 8 . 7 5 7 . 2 4 3.9 8 8 . 0 1 2 1 . 0 7 9 - . 0 7 9
1 . 0 5 6 —1 . 0 5 6 ' 1 . 3 1 0 - 1 . 3 1 01 . 0 7 4 - . 0 7 4 ' 1 .3 7 0 - . 3 7 01 . 0 4 3 - 1 . 0 4 3 1 .1 7 5 - 1 . 1 7 5
• 963 — . 9 6 3 . 6 4 3 - . 6 4 3- . 0 4 9 . 0 4 9 .1 96 - . 1 9 6
. 2 5 7 - . 2 5 7 • 061 - . 0 6 1
.5 1 4 - . 5 1 4 .1 6 6 - . 1 6 6• 722 - . 7 2 2 • 426 — .4 2 6.8 8 1 - . 8 8 1 .7 6 1 - . 7 6 1. 9 9 1 . 0 0 9 1 . 0 8 7 - . 0 8 7
1 . 0 5 1 —1 . 0 5 1 1 .3 2 4 - 1 . 3 2 41 . 0 6 2 - . 0 6 2 1 .3 8 8 - . 3 8 81 . 0 2 4 - . 0 2 4 1 . 1 9 7 - . 1 9 7
.9 3 6 .0 6 4 . 6 7 0 . 3 3 0- . 0 2 9 .0 2 9 ' • 183 - . 1 0 3
. 2 7 0 .7 3 0 .0 50 . 9 5 0
.5 2 0 - . 5 2 0 • 155 - . 1 5 5
. 7 2 0 - . 7 2 0 • 416 - . 4 1 6• 872 1 . 1 2 8 .7 5 1 1 . 2 4 9• 974 .0 2 6 1 . 0 7 8 . ' - . 0 7 8
1 . 0 2 7 . 9 7 3 1 . 3 1 5 . 6 8 5 •1 . 0 3 1 - . 0 3 1 1 . 3 8 0 - . 3 8 0
.9 8 5 .0 1 5 1 . 1 9 0 - . 1 9 0
. 8 9 1 - . 8 9 1 .6 6 3 — .6 6 3— • 028 . 0 2 8 . 1 7 1 - . 1 7 1
.2 6 4 - . 2 6 4 . 0 3 5 - . 0 3 5. . 5 0 7 ... - . 5 0 7 • 137 - , 1 3 7 . .
. 7 0 0 - . 7 0 0 .3 9 5 - . 3 9 5
. 8 4 4 - . 8 4 4 • 727 - . 7 2 7• 939 1 . 0 6 1 1 . 0 5 1 . 9 4 9. 9 8 5 1 . 0 1 5 1 . 2 8 4 . 7 1 6.9 8 1 3 . 0 1 9 1 . 3 4 5 2 . 6 5 5. 9 2 9 - . 9 2 9 1 . 1 5 2 - 1 . 1 5 2. 8 2 7 • 173 . 6 2 2 .3 7 8
- . 0 4 5 .0 4 5 • 160 - . 1 6 0. 2 3 9 - . 2 3 9 . 0 1 6 — . 0 1 6
161
8 . 0 0 0 ' 3 . 0 0 0 0 . 0 0 0 ' • . 2 6 8 — •2688 . 0 0 0 4 . 0 0 0 0 . 0 0 0 . 3 5 9 - . 3 5 98 . 0 0 0 5 . 0 0 0 0 . 0 0 0 • 451 - . 4 5 18 . 0 0 0 6 . 0 0 0 2 . 0 0 0 . 5 4 2 1 . 4 5 88 . 0 0 0 7 . 0 0 0 5 . 0 0 0 • 633 4 . 2 6 78 . 0 0 0 0 . 0 0 0 0 . 0 0 0 .7 2 5 - . 7 2 58 . 0 0 0 9 . 0 0 0 1 . 0 0 0 .8 1 6 . 1 0 48 . 0 0 0 1 0 . 0 0 0 0 . 0 0 0 • 908 - . 9 0 89 . 0 0 0 1 . 0 0 0 „ 0 . 0 0 0 • 036 — .0 3 69 . 0 0 0 . 2 . 0 0 0 0 . 0 0 0 .1 2 7 - . 1 2 79 . 0 0 0 3 . 0 0 0 0 . 0 0 0 • 218 - . 2 1 89 . 0 0 0 4 . 0 0 0 0 . 0 0 0 • 310 - . 2 1 09 . 0 0 0 5 . 0 0 0 0 . 0 0 0 - .4 0 1 - . 4 0 19 . 0 0 0 6 . 0 0 0 2 . 0 0 0 .4 9 2 1 . 5 0 89 . 0 0 0 7 . 0 0 0 2 .000 . 5 8 4 1 . 4 1 69 . 0 0 0 8 . 0 0 0 . 2 . 0 0 0 ,6 7 5 1 . 2 2 59 . 0 0 0 . 9 . 0 0 0 2 . 0 0 0 .7 6 6 1 . 2 3 49 . 0 0 0 1 0 . 0 0 0 1 . 0 0 0 .850 • 142
1 0 . 0 0 0 1 . 0 0 0 0 . 0 0 0 - . 0 1 4 .0 1 41 0 . 0 0 0 2 . 0 0 0 0 . 0 0 0 . . 0 7 7 - . 0 7 71 0 . 0 0 0 3 . 0 0 0 0 . 0 0 0 • 160 — .1681 0 . 0 0 0 4 . 0 0 0 0 . 0 0 0 . 2 6 0 - . 2 6 01 0 . 0 0 0 5 . 0 0 0 0 . 0 0 0 .3 5 1 - . 3 5 11 0 . 0 0 0 6 . 0 0 0 1 . 0 0 0 • 442 .5581 0 . 0 0 0 7 . 0 0 0 2 . 0 0 0 .5 3 4 1 . 4 6 61 0 . 0 0 0 8 . 0 0 0 0 . 0 0 0 • 625 - . 6 2 51 0 . 0 0 0 9 . 0 0 0 0 . 0 0 0 .7 1 6 — .7161 0 . 0 0 0 1 0 . 0 0 0 • 0 . 0 0 0 . 8 0 8 — .6 0 81 1 . 0 0 0 1 . 0 0 0 0 . 0 0 0 - • 0 6 4 *’ .0 6 41 1 . 0 0 0 2 . 0 0 0 0 . 0 0 0 ' .027* - . 0 2 71 1 . 0 0 0 3 . 0 0 0 0 . 0 0 0 • 118 - . 1 1 81 1 . 0 0 0 4 . 0 0 0 0 . 0 0 0 • 210 • - . 2 1 01 1 . 0 0 0 5 . 0 0 0 ' . 0 . 0 0 0 • 301 — . 3 0 11 1 . 0 0 0 6 . 0 0 0 2 . 0 0 0 .3 9 2 1 . 6 0 8
. 4 7 5 - . 4 7 5
.6 6 1 - . 6 6 1 ' •• 798 - . 7 9 8 •• 886 1 . 1 1 4 1 .. 9 2 4 4 . 0 7 6 1.. 9 1 3 - . 9 1 3 1.• 853 . 1 4 7 1..744 - . 7 4 4 .
- . 0 8 1 .0 8 1 0. 1 9 6 - . 1 9 6 - •. 4 2 5 - . 4 2 5 ♦.6 0 3 — .60 3 •.7 3 3 - . 7 3 3 e. 8 1 4 1 . 1 8 6 .. 8 4 5 1 . 1 5 5 1.. 0 2 7 1 . 1 7 3 1.. 7 6 0 1 . 2 4 0.6 4 3 . 3 5 7 •
- . 1 3 5 • 135 •.1 3 5 - . 1 3 5 - •• 356 - . 3 5 6 •. 5 2 7 - . 5 2 7 t •. 6 5 0 - . 6 5 0 •.723 . 2 7 7 •. 7 4 7 1 . 2 5 3 1.• 722 * - . 7 2 2 1 .. 6 4 7 — »u47 e. 5 2 3 - . 5 2 3 •
- . 2 0 8 .208 ..0 5 5 • - . 0 5 5 — .• 268 - . 2 6 8 - •. 4 3 3 - . 4 3 3 •. 5 4 8 - . 5 4 0 •. 6 1 4 1 . 3 0 6 •
-•Ill - • 3 6 2 — • 6 8 6
• 997 3 . 7 7 1
- 1 . 2 8 3- . 0 8 2- . 5 4 5- . 1 4 7
• 008 *— •076 - . 3 1 5- . 6 2 9 i1 . 0 6 b
• 850• 808
1 . 0 2 0. 5 6 9
- . 1 3 1. 0 3 9
- . 0 3 0- . 2 5 5- . 5 5 3
. 1 5 7
.9 5 7- 1 . 0 7 0
— . 8 4 3 - . 2 7 0 - . 1 1 2
. 0 7 7
. 0 2 7- . 1 7 8- . 4 5 81 . 2 7 1
111362686003229283082545147008076315629934150192980431131039030255553843043070843278112077027178458729
162
1 1 . 0 0 0 7 . 0 0 0 0 . 0 0 0 .4 8 41 1 . 0 0 0 8 . 0 0 0 0 . 0 0 0 . 5 7 51 1 . 0 0 0 9 . 0 0 0 0 . 0 0 0 . 6 6 71 1 . 0 0 0 1 0 . 0 0 0 0 . 0 0 0 . 7 5 81 2 . 0 0 0 1.000 0 . 0 0 0 - . 1 1 41 2 . 0 0 0 2 . 0 0 0 0 . 0 0 0 - . 0 2 31 2 . 0 0 0 . ; 3 . 0 0 0 • 0 .000 .0 6 91 2 . 0 0 0 4 . 0 0 0 0 . 0 0 0 • 1601 2 . 0 0 0 5 . 0 0 0 0.000 . . 2 5 11 2 . 0 0 0 6 . 0 0 0 0 . 0 0 0 .3431 2 . 0 0 0 7 . 0 0 0 0 . 0 0 0 •- .4 3 41 2 . 0 0 0 8 . 0 0 0 0.000 . 5 2 51 2 . 0 0 0 9 . 0 0 0 0 . 0 0 0 . 6 1 71 2 . 0 0 0 1 0 . 0 0 0 0 .000 .7 0 81 3 . 0 0 0 1 . 0 0 0 0 . 0 0 0 - . 1 6 41 3 . 0 0 0 2 . 0 0 0 0.000 - . 0 7 31 3 . 0 0 0 3 . 0 0 0 0.000 . 0 1 91 3 . 0 0 0 4 . 0 0 0 0 . 0 0 0 .1 1 01 3 . 0 0 0 5 . 0 0 0 1.000 . 2011 3 . 0 0 0 6 . 0 0 0 0 . 0 0 0 .2 9 31 3 . 0 0 0 7 . 0 0 0 1 . 0 0 0 . . 3 8 41 3 . 0 0 0 8 . 0 0 0 0 . 0 0 0 .4 7 51 3 . 0 0 0 9 . 0 0 0 . 1.000 • 5671 3 . 0 0 0 1 0 . 0 0 0 0 . 0 0 0 .6581 4 . 0 0 0 1.000 0.000 - . 2 1 41 4 . 0 0 0 2 . 0 0 0 0 . 0 0 0 - . 1 2 31 4 . 0 0 0 3 . 0 0 0 0.000 . - . 0 3 11 4 . 0 0 0 4 . 0 0 0 0 . 0 0 0 ' .0601 4 . 0 0 0 5 . 0 0 0 0 . 0 0 0 .1511 4 . 0 0 0 6 . 0 0 0 ’ 0.000 .2 4 31 4 . 0 0 0 7 . 0 0 0 0 . 0 0 0 .3 3 41 4 . 0 0 0 6 . 0 0 0 0.000 . 4 2 51 4 . 0 0 0 9 . 0 0 0 0 . 0 0 0 : . 5 1 71 4 . 0 0 0 1 0 . 0 0 0 0 . 0 0 0 • 608
.4 8 4 • 631 — ..575 • 598.6 6 7 . 5 1 6.758 .3 8 5 ; - .. 114 - . 3 0 0 •
• 023 - . 0 4 4 .••069 .162. 1 6 0 . 3 2 0.2 5 1 - . 4 2 7. 3 4 3 . 4 8 6 '
- . 434 . 4 9 6 — •• 525 . / . 456 - •,617 . 3 6 7 . - •.7 0 8 . 2 2 8 — •.164 - . 4 1 0• 073 - . 1 6 1 •
. 0 1 9 .0 3 8
. 1 1 0 .188 - •
. 7 9 9 • 288 •.293 .3 4 0.6 1 6 . .3 4 2 •. 4 7 5 * .2 9 5 — •• 433 . . . .1 9 9 •.658 • 053 - •. 2 1 4 - . 5 3 8 . •• 123 • - . 2 9 7• 031 — .1 0 5 •. 0 6 0 .0 3 8 - •.1 5 1 .131.2 4 3 ♦ 175 — •.334 • 170. 4 2 5 . 1 1 6 - •• 517 • 012 — ••608 - . 1 4 1 , •
• 909 . - . 9 0 9. 9 1 7 - . 9 1 7.6 7 0 - . 6 7 0• 087 - . 0 8 7.0 8 8 - . 0 8 8.12 4 . 1 2 4. 0 9 7 . 0 9 7.0 8 5 - . 0 8 5.34 2 - . 3 4 2 -. 5 9 0 - . 5 9 0. 7 4 7 * - . 7 4 7.7 3 2 - . 7 3 2.4 61 - . 4 6 1.146 .1 4 6.0 5 8 - . 0 5 8.1 8 1 . 1 8 1.18 1 . 1 8 1. 0 2 6 . 0 2 6• 204 . 7 9 6.42 4 - . 4 2 4.5 5 5 . 4 4 5.5 1 2 - . 5 1 2• 215 • 705.4 2 0 ' . 4 2 0.0 2 0 - . 0 2 0.2 4 9 • 249.2 8 0 • 280.1 5 6 . 1 5 6.042 - . 0 4 2. 2 3 2 - . 2 3 2.3 3 1 - . 3 3 1. 2 5 7 - . 2 5 7.0 7 1 . 0 7 1. 7 3 7 • 737
631598516385300044162320427406496456367220410161038188712340658295001053538297105038131175170116012141
163
TREND SURFACE ALAMOS MINING DISTRICT
RIOT OF ORIGINAL DATA <Z-COOROlNATE$)
164
PLOTTING LIMITS MAXIMUM X • MAXIMUM T ■
I t .O O O O O O1 0 .0 0 0 0 0 0
MINIMUM X MINIMUM T
1.0000001.000000PLOTTED VALUES HAVE BEEN MULTIPLIED BT A FACTOR OF 10 TO THE
T-SCALE IS HORIZONTALT-VALUE • 1 .0 0 ♦ .0657 X (SCALE VALUEl
X-SCALE IS VERTICAL1 0 9 ° 0 0 '
012 5A56TB9 1Z1A567B9 1Z3A56789 1ZSA56789 121*56769 121*56789 121*56789 121*56789 121*56789 121*56(719 121*56789
1 .0 0 *0 1.1*1 .2 9 1*11 .5 71 .71 1 . 8 6 <0 2 . 0 0 2.1*2 .2 9 2. *12 . 5 72 .7 12 . 8 6 *1000 1 . 0 0 1.1*1 .2 9 1*11 .5 71 .71 1 . 8 6 «0 * . 0 0 * . l ** . 2 9 * . * 1 * . 5 7 * .7 1 * . 8 6 *05 . 0 0 5 .1 *5 . 2 95 . * V5 . 5 75 .7 1 5 . 6 6 +06 . 0 06 . 1 *6 . 7 96. *16 . 5 76 .7 16 . 8 6 *07 . 0 0 7 . 1 *7 .2 9 7 .* 17 . 5 77 .7 17 . 8 6 *08 . 0 06 .1 *6 . 2 9 8 *18 . 5 78 .718 . 8 6 «0 9 . 0 0 9 . 1 *9 . 2 99. *1 9 .5 79 .7 1 9 . 8 6 *0
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LIST OF REFERENCES
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08 84 5
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E X P L A N A T I O N
Csv
Quaternary. Al luvium, soils & gravel.
Tertiary continental & Upper Cenozoic clastic rocks . Conglomerate and f anglomerate, include Baucar it Formation.
Unco n f ormity
Upper Cenozoic volcanic rocks. Mostly flows of basic composition , basalts, ande sites, aglomerates and tuf fs .
mMiddle Cenozoic volcanic rocks. Mainly flows of acidic composition; rhyolites.ignimbrites and tuffs.
U nconform i ty
Lower Tert iary-Upper Cretaceous intrusive rocks . ( La ramide ) PrincipalJy batholits of granitic - granodioritic composition .
Cii
Pmet
Cretaceous rocks . Include limestones, shales, sandstones and
i ntcr bedded tu f fs . Potrero & Palmar formations.
Undifferentiated Mesozoic rocks . Mostly rocks of sedimentary origen .
T riassic - Jurassic rocks. Include quar tz i tes , coal bearing or
graphitic shales, and minor marine limestones .B arranca formation
Uncon fo r m i t yPaleozoic metamorphic rocks represented by
gneisses,schists, and metavolcanic and sedimentary rocks.
Undifferentiated Paleozoic rocks . Include limestones , shale s
and sandstones. C c r ro P r ie to & P rovccdora fo rm a t io n s .
Undifferent ia ted Prccambr ian rocks . Older Pre Cambrian is
represented by Pinal schist ,metavolcanics,shale and limestones.
Younger Precambrian consists of shale, limestone and dolomite.
Geologic contact
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E X P L A N A T I O N
Z
Oral
Qdt
Teg
Tv
T rio
Cand
V Cgr
Cclza
I met
GEOLOGIC SYMBOLS
Alluvium
Residual soils
Ta l u s
C o n g l o m e r a t e , s a n d . B a u c a r i t F o r m a t i o n .
unconformity
Basalts and basic volcanic agglomerates
Andesites, rhyol ites and pyroclasts
Rhyolites and rhyolitic tu f fs unconformity
Porphyritic andesite
Granit ic batholith
Limestones, sometimes metamorphosed
Metasediments: limestones, shales and
sandstones with intense metamorphism.
Barranca Formation ( ? )
r Strike and dip
Geologic contact
Inferred contact
Fault or f racture
Inferred fault
TOPOGRAPHIC SYMBOLS
River
Stream
m z Dam
Paved road
T own
Vil lage
Center of aerial pothograph
Flight line
Index map
1 2 3 4K i to m eters
6 E 0 L 0 G I C MAP,
AL AMOS MI NI NG DI STRI CT
SONORA, M E X I C O
F i g u r e 6
1 0 9 * 1 5 ' 109*10 ' 1 0 9 * 0 5 ’
Adalberto Vazquez P, M S.Thesis,Dept of Min &Geol.Eng. 1975.
29
400
00 m
N< s \
\ / r i_______ _^ARoncho Son SiUes t re
\ M V)T««or txhic' '< “ o c o , j h u i 4 / O L o s C o * V d o l o r o d o .
^ V o S o n A n t o n i o
f R o n c N o H u i ^ b c W'i— r
NARANJlX ffuncho t
Zopofe'
,E I Cupn MINER ALOdlCAL GROUPS OF MINES
S ie r r a de Alamos
XICANAr ra las Plomosas/ * *
V E T A C M A N O tpifbRAsx Verdes
\ \ | 3 |Lomas los Tongues
STerra del Chapote
S i e r r a del B a v is p e
E l HI 6 0
err a San Bernardo
'SH f 2«u« L V»ANvV
CERRO BLANCO
Rcfc*. H u n m u c i
rARIA^RcM. ^Sebeyohuj VERDE
CHAPOTES^ LR TE h EDIONOA
^ PICHtCUATE v lO LC Ti
2 9 7 —
A r e a mapped
Geologic MapTCff\ 7. Wiyi awthe A k f m o s ^ ) i s t r i c t .
296
LOCATION AND GROUPING
OF MINES W H IT IN THE
A L A M O S DISTRICT,
SONORA, M E X IC O .
k i lo m e t e r s
F igure 14
72 Adalbert© Vazquez P.,M.S.Thesis, Dept of Min. A. Geol.Eng.1975.