report rborne vlf/em - british columbia
TRANSCRIPT
ISLAND GOLD EXPLORATIONS LTD. OWNER AND OPERATOR
A GEOPHYSICAL REPORT
SURVEYS OVER THE S.E.I. MINERAL CLAIM COVERING A1 RBORNE MAGNETOMETER - VLF/EM
SKEENA MINING DIVISION BRITISH COLUMBIA
Latitude 53O15'N; Longitude 13Z0O0'W
N. T. S. 103F/8E% and 103G5WL,
G . H . RAYNER, P.Eng.
TABLE OF CONTENTS
Page
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . 1
LOCATION AND ACCESS . . . . . . . . . . . . . . . . . 1
AIRBORNE SURVEY TECHNIQUES (Woolverton) . . . . . . . 3
SPECIFICATIONS; SABRE AIRBORNE MAGNETOMETER . . . . . 5
SPECIFICATIONS; SABRE AIRBORNE VLF/EM SYSTEM . . . . . 6
DISCUSSION OF RESULTS . . . . . . . . . . . . . . . . 7
SUMMARY A N D CONCLUSIONS . . . . . . . . . . . . . . . 7
STATEMENT OF COSTS . . . . . . . . . . . . . . . . . . 9
CERTIFICATE . . . . . . . . . . . . . . . - . . . . . 10
FIGURES
Location Map
VLF/EM Survey, Par t I
VLF/EM Survey, Par t I1
Magnetometer Survey P a r t I
Magnetometer Survey Par t I1
2
In pocket 11 11
I 1 11
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INTRODUCTION
The S.E.I. Mineral claim of 16 units i s presently owned and operated by Island Gold Explorations Ltd. type gold mineralization i n Yakoun volcanic rocks of Middle t o Upper Jurassic age. 10 meters. of the s t ructures i n e a r l i e r years. No work has been carried out on the ground since about 1930.
The claim covers an area containing vein-
The deposits a re shear controlled w i t h widths of up to There has been limited surface and underground work on some
In November 1979 a helicopter-borne Mag-VLF/EM survey was flown over the property i n an e f f o r t to extend knowledge of existing mineralized s t ructures and to detect other s t ructures under shallow overburden cover.
In addition i t was hoped that the magnetometer component of the survey would help i n discriminating between the favourable Yakoun host rocks and other l e s s favourable intrusive u n i t s known to occur on the property.
In this report the section en t i t l ed "Airborne Survey Techniques" i s a f t e r R. Woolverton.
LOCATION AND ACCESS
The property i s located on the southeast corner of Graham Island i n the Queen Charlotte Islands of British Columbia. The specif ic location i s 53"15' North Latitude; 132"OO'West Longitude.
Pacif ic Western Air1 ines provides a i r passenger service to Sandspi t on Moresby Island on a daily bas i s from Vancouver. by paved road and fe r ry t o a point about one kilometer to the e a s t of the S.E.I. claim just north of the vi l lage of Skidegate. A rough t r a i l leads from this point t o the property.
From S a n d s p i t access i s
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0 R. WOOLVERTON
R. C. O'BRIEN
GEOLOGIST, P.ENG.
FIELD SUPERVISOR
C O N T R A C T E X P L O R A T I O N
5424 HALIFAX ST.. BURNABY 2, B.C., CANADA, PHONE - 299-6998
AIRBORNE SURVEY TECHNIOUES
Evergreen Explorations L t d . I s ai rborne geophysical system can be mounted
A Hughes 500-D i s i n any hel icopter t ha t has two forward sea ts next t o the p i l o t and su f f i c i en t space ahead of -them f o r the geophysical instrument console. preferred. A f i f t y foo t cable connects the instruments t o a " b i r d " w h i c h is towed under the a i r c r a f t . The torpedo-shaped b i r d is approximately f ive f e e t long, e i g h t inches i n diameter, w i t h four t a i l fins mounted inside a 12 inch diameter t a i l section. The b i r d weighs approximately 50 lbs and, except fo r an orange nose, i s painted w i t h a lampblack lacquer mixture to reduce s t a t i c b u i 1 d-up .
The magnetometer i s connected t o a Bausch and Lomb V . O . M . -5 char t recorder which i s normally operated a t a char t speed of 5 inches per minute. The recorder is place on the sea t between the p i l o t and the operator s o t h a t the ground control f iducial points and o ther information can be writ ten on the char t d u r i n g f l i g h t . A battery operated 2 channel B r u s h 222 is used t o record the E.M. da ta . Since the event marker i s connected to both the mag and E.M. recorders, the notes and f iducial numbers recorded on the mag chart d u r i n g the survey can be transferred to the E.M. tapes a f t e r each f l i g h t . T h u s the E.M. recorder doesn't have to be e a s i l y reached by the operator during f l i g h t and i s normally mounted on a rack i n the back s e a t behind the operator 's head.
Ground control f o r an airborne survey i s achieved by u s i n g " f l i g h t str ips" which a re a i r photo strip-mosaics constructed w i t h topographic map control s o t h a t s t r a i g h t l ines on the f l i g h t strips are approximatley s t r a igh t l i nes on the ground. T h i s i sn ' t always achieved, of course, due t o d i s tor t ion i n the photos and, more often, scale var ia t ions produced by topographic r e l i e f .
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After the f l i g h t lines are plot ted on the f l i g h t s t r i p mosaic they are flown as exactly as possible by combining a carefully followed a i r c r a f t heading w i t h visual corrections where necessary. As the hel icopter passes over each swamp. creek, o r other recognisable feature ( f iduc ia l point) , t ha t can be- located on the f l i g h t s t r i p , the operator t r iggers the event marker which simultaneously produces a small mark on the edge of the mag recorder char t and one on the edge of the E.M. recorder chart . The f iduc ia l points a r e consecutively numbered on the mag chart during f l i g h t and are also plot ted on the f l i g h t s t r i p . control points f o r making a magnetic contour map.
They are l a t e r plot ted on a base map and become the
Fl ight l ines ra re ly cross one another u s i n g this technique, since i t is a simple matter t o break-off when the a i r c r a f t has veered too f a r off l i n e , f l y back t o the l a s t f iducial point and t r y again. a reas , i t is often necessary to f l y a l i ne several times unt i l i t "comes out'' where i t s supposed t o . Even i n these extreme cases, experience over the pas t decade has shown t h a t magnetic features can be located t o well w i t h i n 100 metres.
In f l a t , featureless
Survey l i nes are flown from 200 t o 400 metres apa r t depending upon the de t a i l required. In s teep mountainous a reas , t e r r a in clearance is l imited by the climbing a b i l i t y of the he l icopter so t h a t as a general rule the magnetic readings obtained over mountain peaks and ridges a re s l i g h t l y h i g h and those obtained over narrow valleys a re correspondingly low.
The " b i r d " is kept as close t o the t r e e tops as possible.
Periods of magnetic f i e l d disturbances due t o sunspot ac t iv i ty a r e avoided by monitoring the forecasts on shor t wave s t a t i o n WWV, i n Boulder, Colorado. Diurnal var ia t ions a r e eliminated by zeroing the magnetometer a t a l t i t u d e imnediately a f t e r take-off. If t h i s i s done a t about the same location on each f l i g h t , i t i n e f f e c t becomes a base s t a t i o n .
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SPEC1 FICATIONS: ' SABRE A I R B O R N E MAGNETOMETER
TYPE : Proton Precession.
RANGE: 20,000 t o 75,000 gammas.
REPETITION RATE: Approximately 1 second.
OUTPUT:
DISPLAY:
Designed t o operate in to any potentiometri c chart recorder w i t h 0 - 0.1 v o l t scale .
D i g i t a l dial + analog meter. Meter shows l a s t 1000, 2000, or 5000 gamma of to ta l f i e l d depending on scale selected. Zeroing system allows chart recorder pen t o be positioned anywhere on paper so tha t i f pen i s centered, the resul t ing scales t h a t can be selected are 2500, k1000, and +2500 gamma. These scales are standard b u t v i r tua l ly any other can be provided.
RESOLUTION : Resolution of instrument i t s e l f is be t t e r than 1 gamma b u t ultimate resolution depends on accuracy of char t recorder.
DETECTOR: . Kerosene-filled co i l , 9cm x 8cm diameter. Inductance 60 mill ihenries, resistance 7.5 ohms, weight 2.2 kilograms.
OPERATING TEMPERATURE : Instrument: -1OOC t o +6OoC. Detector : -4OOC t o +6OoC.
DI MENS I ONS : Instrument Console: 30xlOx25cm, weight 3.5 kilograms. Towed Bird: 1.7m x 21cm diameter, weight 30 kilograms. (VLF/EM antenna system is housed i n b i r d along w i t h mag detector).
POWER SOURCE : 2 - 12 volt - 20 AH lead-acid ba t te r ies .
MAN U FACTURE R : Sabre Electronic Instruments Ltd. 4245 East Hastings S t r ee t , Burnaby, B. C.
Phone: 291-1617
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SPEC1 FI CAT1 ONS : SABRE A1 RBORNE VLF/EM SYSTEMS
ANTENNA SYSTEM: 2 separate omnidirectional arrays, housed i n same b i r d as proton magnetometer detector.
PARAMETERS MEASURED: Horizontal f i e l d strength on 2 s ta t ions simil taneously. Designed f o r use i n steep terrain where d i p angle infor- mation i s confusing and often useless.
FLIGHT LINE DIRECTION: Since antenna systems are n o t d i rect ional , f l i g h t l ines can be placed i n most convenient location.
STATIONS AVAILABLE: Any 2 VLF stations can be used. Usually Sea t t l e and Annapolis are chosen f o r use i n B. C. these 2 s ta t ions is large enough so t h a t v i r tua l ly a l l conductors are energized by one o r the other) .
(The angle between
TYPE OF READOUT: 2 analog meters, one fo r each s t a t ion , and 2 recorder outputs a t rear of console.
RECEIVER CONSOLE: 2 separate receiver channels, b o t h housed i n 3Ox10x25cm case.
OPERATING TEMPERATURE RANGE: Instrument console: - lO°C t o +5OoC. Antenna sys tern:
Antenna Sys tern:
-4OOC t o +5OoC (when f i t t e d w i t h low temperature integrated c i r cu i t ry ) .
2 - 9 vol t t r ans i s to r ba t t e r i e s i n standard version, type lead-acid ba t te r ies i n low temperature version.
POWER SOURCE: 2 - 6 vo l t gel
Receiver console: 8 alkaline penl i te ce l l s w i t h l i f e o f 100 hours.
MANUFACTURER: Sabre Electronic Instruments, L t d . , 4245 East Hast ings S t r ee t , Burnaby, B. C.
Phone: 291-1617
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DISCUSSION OF RESULTS
The VLF/EM component of the survey returned numerous modest conductors i n the northern pa r t of the survey where geological control i s poor. In
the southern pa r t of the survey where mineralized s t ruc tu res a re known t o occur the r e s u l t s were generally disappointing. The main known s t ruc - ture would p lo t about 1,200 meters west o f the seashore on Line 2E. has a trend of about 340" and i s ve r t i ca l t o steep. a modest anomaly a t this location b u t not a s marked as an t ic ipa ted . There i s no VLF/EM response along the projected strike of this s t ruc tu re on Lines 1 E o r 3E. the known s t ruc tu res i s not pa r t i cu la r ly conductive.
I t On Line 2E there i s
I t would appear t h a t the f ine ly divided py r i t e i n
In the northern pa r t of the survey the l a rge r number o f conductors located was unexpected and i s not c l ea r ly understood. a c t i v i t y in this area and i t may be t h a t the conductors r e f l e c t intrusion- re la ted shearing within bo th the in t rus ives and the enclosing Yakoun Formation. f o r some of these conductive zones however they m u s t be followed up with ground EM before anything del i na t e can be concluded.
There i s some intrusive
There i s a suggestion of a norther ly o r northwesterly trend
The magnetometer component o f the survey out l ined the in t rus ive areas i n a general way b u t not with s u f f i c i e n t c l a r i t y t o improve on previous knowledge of in t rus ive d i s t r ibu t ion .
SUMMARY AND CONCLUSIONS
The airborne VLF/EM survey ind ica tes several modest conductors within the area covered. o r northwesterly. west of the seashore appears ' to correspond t o a shear s t ruc tu re known from old workings on the ground. on l i n e s t o the north o r s o u t h . I t would appear t h a t the f i n e py r i t e disseminations i n this type of shear zone a r e not pa r t i cu la r ly conductive.
The general trend of the conductors appears t o be northerly One o f the poorer conductors on Line 2E, 1,200 meters
No extensions of this s t ruc tu re a reseen
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Further ground EM surveys will be required i n the northern p a r t of the survey t o more accurately locate and di l ineate the numerous conductors indicated i n this area. Physical ground follow-up will be required to determine t h e i r cause.
The magnetometer component of the survey outlined the intrusive areas i n a general way b u t did not improve on previous knowledge of intrusive d i s t r i b u t i o n . The shear s t ructures do not show a magnetic response.
Respectfully submit
G . H . RAYNER, P. June 20, 1980
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STATEMENT OF COSTS
Airborne magnetometer - VLF/EM survey Compl e ted November 16 , 1 979 48 l ine-miles a t $60 per l ine-mile
Report preparation, G . H . Rayner, P.Eng. 5 days a t $350 per day
$2 , 880.00
1,750.00
$4,630.00 TOTAL
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CERTIFICATE '
I , Gerald H. Rayner do hereby c e r t i f y tha t :
1 . I am a consulting geological engineer with o f f i ces a t 626 Duchess
Avenue, West Vancouver, B . C .
2. I am a graduate of the University of Br i t i sh Columbia (B.Sc. Geology).
3. I am a member in good standing o f the Association of Professsional
Engineers of the Province of Br i t i sh Columbia.
4. I have practiced my profession s ince 1958 primarily i n Western North
America and the South Pacif ic .
5. This report i s based on personal f ami l i a r i t y with the work and upon v ,
several v i s i t s t o the property over
June 10, 1980
the past f i
G.
ve years.
H. RAYNER West Vancouver, B . C .