DEPARTMENT OFMINERALS AND ENERGY 056283

BUREAU OF MINERA.= RESOURCES,GEOLOGY AND GEOPHYSICS

Record 1975/68

SOIL SAMPLING AT THE JUBILEE PLUNGER GOLD PROSPECT 9 FORSAYTH,

NORTH QUEENSLAND

K.J. Armstrong

BMRRecord1975/68

3

The information contained in this report has been obtained by the Department of Minerals and Energyas part of the policy of the Australian Government to assist in the exploration and development ofmineral resources. It may not be published in any form or used in a company prospectus or statementwithoutthe permission in writing of the Director. Bureau of Mineral Resources, Geology and Geophysics.

Record 1975/68

c.

SOIL SAMPLING AT THE JUBILEE PLUNGER GOLD PROSPECT, FORSAYTH,

NORTH QUEENSLAND

by

K.J. Armstrong

CONTENTS

SUMMARY

INTRODUCTION

PHYSIOGRAPHY AND CLIMATE

GEOLOGY

MINING HISTORY

PREVIOUS INVESTIGATIONS

SAMPLING TECHNIQUES

ANALYTICAL TECHNIQUES

Sample preparation

Digestion

Analysis

DISCUSSION CV RESULTS

CONCLUSIONS AND RECOMMENDATIONS

REFERENCES

FIGURES

1,^Jubilee Plunger lode - geology and sample locations

2. . Silver anomalies in soils surrounding the Jubilee Plunger lode

3. Gold anomalies in soils surrounding the Jubilee Plunger lode

4. Copper anomalies in soils surrounding the Jubilee Plunger lode

5. Lead anomalies in soils surrounding the Jubilee Plunger lode

6. Zinc anomalies in soils surrounding the Jubilee Plunger lode

7. Silver values on detailed traverses across the lode

8. Copper values on detailed traverses across the lode

9. Lead values on detailed traverses across the lode

10.^Zino values on detailed traverses across the lode

Page

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SUMMARY

Extensive silver, gold, copper, lead, and zinc anomalies associated

with the Jubilee Plunger reef suggest that soil sampling is a useful technique

for gold exploration in the Forsayth area of north Queensland. The old workings

at Jubilee Plunger are all very shallow, and the deposit has been only

superficially tested. Although indications are that the lode is of low grade,

it is of considerable size (1100 m long and averaging 40 m wide), and drilling

is recommended.

INTRODUCTIOW

During the 1973 and 1974 field seasons a geochemical soil sampling

program was undertaken at the Jubilee Plunger reef, the site of abandoned

gold working* about 30 km south-southeast of Forsayth, north Queensland

(Fig. 1). The lode was chosen for detailed study because of its substantial

size.

The major objective of the survey was to determine the geochemical

expression of the deposit, and thereby assess the usefulness of soil sampling

as an exploration technique for gold in the Forsayth region.

PHYSIOGRAPH'f AND CLIMATE

Relief over the survey area is not great. The highest hilltop

(Fig. 1) is about 30 m above thshgeneral level of the countryside. A

smaller hill of about 8 a relief occurs in the southern central part of the

grid area. The land to the north, east, and south is relatively flat;

sandstone ridges are prominent to the west.

The climate is hot with average daily maximum temperatures exceeding

32 0C during both December and January. The mean winter temperature (June-

August) is 15°C to 21 °C. Average annual rainfall is about 650 mm, most of

which falls during summer storms.

GEOLOGY

The country rock is a biotite granodiorite (Robin Hood Granodiorite)

of probable early Palaeozoic age. The gold mineralization is associated with

lead and zinc sulphides and occurs in a quartz-veined greisen. The greisen

is about 1200 a long, averages 40 m wide, and dips east at between 350 and

60°. At the surface it is commonly ferruginous (Bain, Oversby, & Withnall,

in prep.).

I I I I I I I I I I I I I I I I I I I I

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MINING HISTORY

Mining records for the area are insufficiently detailed to position

old mines aocurate ly, as m&DT aa three gold mines may have been within the

limits or the eoil grid - the Jubilee Plunger, Lad7 Mary, and Better Luok.

Dooumented production from these ie listed below:

Jubilee Plunger

Better Luck

Ore Crushed (tonnes)

996.3

669.6

737.1

Gold Bullion (grams)

10096

15642

20611

!he mines were worked between 1894 and 1897 (Witbnall, in prep.).

PREVIOUS IRVESTIGATIOBS

Exploration during 1970 b7 Oul! Minerals Pt7 Ltd consisted of

detailed mappiDg of the workings, and the bulldoz1Dg of 13 shallow costeans

across the locie. The poor gold Taluae (aTerage 1 g/tonne (0.04oz/ton),

maximum 4.4g/toaoe (0.14os/ton» enoountered in rock-chip samples from the

area disoouraged further work (Gulf Minerals Pt7 Ltd, 1970).

SAMPLING TECBM9,UES

A reotilinear grid (Pig. 1) was survered using a prismatio oompass

and measuring tape. Samples were taken everr 150 II parallel to the ree! and

ever" 50 II atright-anglea to it. The oentral site on each orose-line was

marked with a star pioket and numbered tag. Three detailed traverses across

the lode with sample epacings or 5 and 10 • were also aade. A total of 162

IBI-horizon soil samples vere oollected using a miners t pick. Eaoh sample

consisted ot about 200 g or material, and was taken from a depth ot 15-20 cm.

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ANALYTICAL TECHNIQUES

All sample preparation and analytical work excluding gold

determinations were carried out in the BMR laboratories.

Sample preparation

The soil samples were moist and required drying in an air oven

at 60°C for 24 hours. The dry material was sieved to minus 500 micron

(30 mesh BSS).

Digestion

Perchloric (6m1, 1:1) and hydrofluoric (10m1, 40%) acids were

added to a platinum basin containing the sample (1.000 + .003 g). Hydrochloric

acid (5m1, 1:1) was then added and residue was dissolved by gentle heating.

On cooling, the contents of the basin were made up to 25 ml in a volumetric

flask,

Analysis

The samples were analysed for silver, copper, lead, and zinc using

a Varian AA4 atomic absorption spectrophotometer. Non-atomic absorption

corrections were made for low concentrations of lead and zinc.

Gold was determined at AMMEL by atomic absorption following 'aqua

regial (hydrochloric and nitric acids) digestion and organic (DIBN) extraction.

DISCUSSION OF RESULTS

The silver, gold, copper, lead, and zinc contents of the soils of

the area are shown in Figures 2-6. Anomalies appear to be adequately

delineated by contour values of 1 ppm Ag, 0.1 ppm Au, 30 ppm Cu, 140 ppm Pb,

140 ppm Zn. The two larger anomalies (A and B) are separated by a zone of

alluvium but geophysical work (Hone, pers. comm., 1975) suggests that

mineralization is continuous between them at depth. Together, anomalies A

and B are over 1100 m long and up to about 250 a wide.

I ~-

I • •

I • • • • •

I ~. ~ • • • •

I • • • •

• • .' • •

I • • •

• I • • • • • •

I ANOMALY 8

I '. " . • • • A~ rE"5ult:s

I n ppm.

7

• • • • • ~ , Contollrs:

I '~ >3ppm(obaekg,.ound) ,C:::J > I ppm( background) ,

•

I Where no value given Ag w •• not detected

• • • • • .. .' • • • « ,ppm)

I I ,, 0 'so • • • • • • • • • • I iIo , .

M.t r ••

I I • •• • • • • • ••

I ANOMALY A

Q 2

I • ., • • ~

I 2 ,; '. ,. • • • • •

Silver anomalies In 5OH. surrounding the lubil.e Plunger'lode

I ' , FIO';r. 2 ReccIFCI 197''''19

. "

L._ MCP" ',69

I Au

I • •

• I '08 • • • ·05 •

I "(p. • • • • • • ' 01) • ·1 •

/J. • .1), .'05

I ." •

\1 .'05

5 • .'05

• • • • • I • •

ANOMALY 8 • • - '10 ~. •

I • • • • • • •

I '05 -05 ·05 • • • • • • • •

I Au resul ts in ppm.

I ·os -os ., ·os -o~ Contour : > 0 ·1 ppm

• • • • • • • • • •

I Wnere no value given Au was not detected

«0-05 ppm)

I ·os

~ • • • • • • • • • ". I I

-IS -05 -OS ·05 0 ISO • • • • • • • • • • . I I .

.... t ,..s

I Traverse 2 -os -65

I • • • • • • • • • · ' ANOMALY A

I -25 . lIS ·os .oS ·05 • • · - ""a~,.stP • • • •

I ·os -OS -,

I • • • • • • • •

Gold anomalie~ In 5Oil5 surround i n9 tne Jubi I~e Plunger lode

I Record 1975/68 "

Figure 3 - - ,. (Pt)l70

I I I I I I I I ,I

I I I I I I I I I I I

, •

Cu

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11 • ((~~. !O

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ANOMALY A

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C,u results In ppm.

Contours:

Ie •

e:m:a > to ppm(x 3 background) c:::J > ~ ppm(bac.kground )

o ISO .. ' -to1~."""-:~-r-.J..' s---"

Copper anom~ljes in soils surrQunding the Jubilee Plunger lode,

Figure 4 M(Pt1l71

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I I I I I I I I I I I I I I I I

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Pb

•

48

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67

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ANOMALV B

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Pb results in ppm.

Contours: em >420 ppm (X3 background) Cl > IltO ppm (bacKground)

o 150

le/!ld ctnomal ies In ~oils surrounding the Jvbil~e Plunger lode.

Rlcord 1975/68 f:i9u~e 5

M(PtJl72

I I I I I I ' I I I I I I I I' I I I I I' I

)

-4-

Traverses 1, 2, and 3 were run across these larger anomalies in

areas least disturbed by mining activity (Fig. 1). The results are shown in

Figures 1-10. Along traverses 1 and 2 the elements generally show ver" high

values in a sone about 30-40 II wide, on either side ot v~ch leyels decrease

sharply but still rell&in anomalous. The extremities ot this peak appear to

correspond with the edges of the greisen zone,suggesting that the greisen

is mineralised acroaa its entire width. Traverse 3 lies where the greisen is

over 100 • vide.

CONCLUSIONS AND RECOMMBNDATIOBS

The geological _pping and the poch.alcal work inclicates that the

mineralized sone is ot sufficient size (i.e., ot the order of 1100 II long by

40 II vide) to warrant further study. All the significant anomalies occur

within the areas ot previ0U8 mining activity, but the old vorkings are only

ver" shallow (less thaD 3 • deep), incl1cat1ng that the deposit has only

been superfioially tested. Bence it is recommended that drilling be carried

out. The first hole should be sited on anomaly B, which gives the strongest

IP response (Hone, pera. oomm., 1915), also it is here that the lode attains

its maximum thickness. Geophysical investigations (Hone, OPe oit.) suggest

that thepreserioe ot a maaaiYe sulphide body is unlikely and the Jubilee

Plunger reet should be regarded primarily as a low-grade large tonnage gold

prospect.

The extensive geochemical anomalies associated with the Jubilee

Plunger lode show that soil sampling and analysiS for silver, gold, oopper,

lead, and zinc oan be a usetul teohnique tor gold exPloration in the Forsayth

area.

I

I I I I

8 .

- - ---.-- - - -- --- -- -- - --- - --. - - ---- --O~----~~------'-----~'-~---'--~--~---r--~--~--~------~------ir-----~i

SS20

. S.mple numbers '4~ ..... .

6

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f .-- - -- -- -- -- -- - ~

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- .- -- - . . -~ -- ._- - --- - -. . .- -- - -- -- -- - -

O~------~-----'-------r--~--~--r--'r-~---r---r--'-----~r-----~------, 554~

7410 ... . ..

8

Traverse 3 ,

.- . E

I~ !! 2 ...... _____ ...

t I I I

- -- -- -- -- .--- , ..:.- ------ - -- - - ~ - - - -- -- -------

O~-----~------~----~~~r-~--~--~---r---r---r--~------~------r-----' 5'64 S&~O

Sampl. numbers 74-JO . '" ..

.. ( Traverstt I in~s - 100 metres long) Figure: 7

Sliver values on det ailed traver~eo; across the lode , The horizontal broken line in eac.h case represents the upper limit of back.ground (I ppm)

Rec:ord 197~/6B M(Pt)l74

I I I I I I

I I I I I I I I I I I I I

no_

Cu

zoo _ Traverse I

t : ~ ' '10_ .;:::

~ I

~ . ., 1 ~ I 'b

<I. ~o ~

-------~ I

~_ =:F"-.....::,-=:::::::::._<="""

(J J"----.,. -'rf---""---r-... ,.----..--r-, -..,--,-,--, ... ,-----.,. -----·,-·- -- -1 ~HO B'.,

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50 ~

Sample numbE'rs 74)0 . ...•

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r-- - - --- -- --- - - -- -- -- -- -- -- ~..,..~=":::.="' . .:-.

o L---""---"T 5;;1.9 ·l---··-T--'---··,.._··· ·_- -,

~'B~

o .....

5 ample number9 7410 ..

Travo.>rst 3

--~ .. ' /'-// "''-.....,

' ___ I_·J

~-----,---~r--,---r--~-,---r---Ir--,---T------,---~r-----, '!ItO

S.",pl. nllrnbeora '..,0 . . ... .

(Tr_ve",. lin", - .o.>",..r., ions)

(opp.r Itaillet 00 dct.lIl'd trAY(-, , .~ aUo)IJ the lode. The horizontal broken line .n ead, "' •• rep,.".e"" the upper limit of b.,lcqr:oll"d ('0 ppm) .

Reur. 197~/6a . """IT!I

c: o

%000

__ 11000 --.~ l. <II Cl 1000

t: o ..... ---'-f ~ q,

'"00

z~oo

2000

Q.. 1000

500

Traverse 1

Sample numbers 74'0 ..... 5520

TraV~r9f" 2

- - - - - - - - - -~-=:!:-==-=-----.... ~= - -~

;-------~------r_----~~~~_,--_T----~--T---~,---r--~----~~----~

Sampl. numbers '410 ... ".

T .. 8verse 3

, ~Do

.' ~----------------.: tz-T---. _ .. ,_.. , , '--"--'-~---r--, ---,--'-'-"--' . , , . I ~ '4- Sampltt numbers 7410 ..... , ~'J!l0

( Traver~e lines - 100 rnetr~s Ions) Fig/Jre :9

ledd values on det,'}iled trtt'.qrS(-lS a(;ro~s the lode. ·'he horizon~al broken line In ettc.h o.;.e repr'(?Se'1ts the upper Iln'ut of backgrO~fld(It"~Jle..",,-L ____ ._,

I I I t::.

~

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I Q.

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,,"00

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Traverse

'200-

'000

80,0

600

~OO

1.00

1000

800

4CO

zoo

1&00

'400

1200

-t-----r----"----.--".----".----".----".----".---,.---.,,r---.---~-"-----r---. "-, 5 , b !;SZO amp e nun"1 ere . 7~30 . . ""

I ~ -.- .. --.----~_r__- '_-,,---r,---Y,-. , , -r'-" ">51.9 SamplEt numbers 7Po .

_ ._------,-----.--- .. • . I

~Inr;

Traverse 3

Icno_

~oo

400 ~ 2001" _______________ . __ _

t. ..-... ,---.---.. -.r--,-.. ...,.. .-~' .. --.T-'. · .. ·r ·_· ... - ·· ·- ·T-·-----,-: "·---·I ~!I'. SamplEl "limbers '430. , . .. " . !lS'O

( Traverse · lines - 100 1l1"~:'''''.~ 10"9 ) Figvre: 10

Z,nc \'all.J~S orr detailed tr"ve~ses a'ros~ the :cde . Tnp h,ril"nt,,( broken ',ne In edc.h case represt>nts the upp('r I'mi t t'f /Jae <:;l"ound (140 ppm).

Record 191'/68 "(P',I17

I I I I I I I I I .1 I .1 J I I I I I I I

-5-

REFERENCES

BAIN, J.H.C., OVERSBY, B.S., & WITHNALL, LV., in prep. - Geology of Forsayth

1,100 000 Sheet area, Queensland. Bur. Miner. Resour. Aust. Rec.

GULF JIlINERALS Pfi LTD, 1910.- Report of prospecting operations, Authority

No. 15~, Poreayth area, Queensland Gsol. Surv. Ql,d Open file

"98 (unpubl.).

WITHNALL, 1. W., in prep. - Mines and lIlineral deposits, li'ors&y'th 1: 100 000

Sheet area, Queenaland. Ceol. Sun. Qld.Reo •.