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File Created: 26-Feb-1992 by Chris J. Rees (CRE)
Last Edit:  07-Oct-1999 by Janet M. Riddell (JMR)

Summary Help Help

NMI
Name AA 1-22, AA, BENTINCK Mining Division Skeena
BCGS Map 092M097
Status Prospect NTS Map 092M15E
Latitude 051º 58' 33'' UTM 09 (NAD 83)
Longitude 126º 41' 03'' Northing 5760883
Easting 659058
Commodities Graphite, Copper Deposit Types P04 : Crystalline flake graphite
Tectonic Belt Coast Crystalline Terrane Undivided Metamorphic Assembl.
Capsule Geology

The AA occurrence is a graphite showing near the southern end of South Bentinck Arm of Burke Channel, 44 kilometres south of Bella Coola. No work on the showing is recorded before 1990, when a ground electromagnetic survey was conducted over the showing which indicated a strong response typical of a steeply-dipping, near surface conductor.

The AA occurrence is located in a belt of dioritic, quartz dioritic and granodioritic gneisses and amphibolite of Paleozoic age, within the otherwise Jurassic to Tertiary Coast Plutonic Complex (Geological Survey of Canada Map 1386A; Assessment Report 21649).

Only the immediate area around the graphite showing has been mapped in detail (Assessment Report 21649). The rocks strike northwest and dip steeply northeast. From northeast to southwest, the area is underlain by fine-grained, garnetiferous gneissic diorite, a strongly sheared metasedimentary unit consisting of argillite, greywacke and local chert, and gneiss and foliated diorite and quartz diorite believed to be derived from Paleozoic sediments and volcanics (Assessment Report 21649). The last unit contains a small felsic intrusive.

Graphite layers are associated with the strongly sheared metasedimentary unit (Assessment Report 21649). A strongly fractured and sheared graphite zone strikes 320 degrees and dips 75 degrees northeast, and is exposed for 10 metres in trench number 1. The rocks here are grey to black, strongly sheared graphitic schists, locally with garnet and quartz veinlets. Some rocks are silicified. Locally the graphite is very coarse, forming large flakes.

Ten 1-metre channel samples were taken across this graphite zone, yielding 13 analyses. Some samples contained up to 25 per cent pyrite, and a trace of chalcopyrite. Carbon ranged from 2.98 to 22.9 per cent; the average of the 13 samples was 12.26 per cent (Assessment Report 21649). This was regarded as adequate to justify further evaluation of the property.

In 1992 Resolute Resources submitted three grab ore samples to Process Research Associates, Vancouver B.C., for preliminary metallurgical tests to determine if the quality was high enough to produce saleable graphite products (Assessment Report 22957). Specifically, the tests were performed to provide high grade +48 mesh, -48 mesh, +100 mesh and -100 mesh, using grinding, flotation, and gravity concentration. Results were:

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Product Grade Yield Carbon

(%carbon) (Weight %) recovery (%)

+48 mesh 92.5 2.08 10.5

48 to 100 mesh 78.3 8.18 35.0

-100 mesh 64.9 11.3 40.0

Total 21.6 85.6

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The metallurgists predicted better recovery results with increased grinding times, and recommended further work on a bulk sample obtained by trenching and drilling.

The prospect was visited and reported on by geologists from the Industrial Minerals Section of the B.C. Geological Survey Branch in 1992 (Fieldwork 1992).

The AA graphite prospect is located on the southern extension of the Work Channel Lineament, as are eight other graphite showings on mapsheet 093D to the north (for example Elcho Harbour, 093D 028 and Grey Giant, 093D 020).

Bibliography
EMPR ASS RPT *21649, *22967
EMPR FIELDWORK *1992, pp. 389-398
GSC MAP 1386A
GCNL #99, 1991; #23, 1992

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