The McMaster prospect is located between the headwaters of Qualark and a western tributary of Ladner Creek, 2.5 kilometres southeast of Spider Peak and 10.5 kilometres southeast of Yale, British Columbia.
The McMaster prospect was found in 1975 as a result of efforts to locate the source of a soil geochemical anomaly outlined by Precambrian Shield Resources Limited. Carolin Mines Ltd., who at that time was developing the Idaho zone 1.5 kilometres to the southeast, gained control of the property in 1976. Trenching exposed discrete quartz-albite-carbonate alteration zones containing sulphides. The style of alteration, mineralization and hostrock sequence were identical to the nearby Idaho deposit (Aurum - 092HNW003). In 1975, a total of 518 metres of diamond drilling in seven holes intersected similar alteration and less abundant sulphides to 91 metres. The McMaster prospect was re-evaluated in 1989 by Athabaska Gold Resources Ltd. Drill core was relogged, trenches remapped and an additional six drillholes totalling 417 metres completed. In 1990, additional trenching was completed.
The area is underlain by an interbedded succession of locally graded siltstone, wacke and coarse volcanic lithic wacke with some discontinuous beds of argillite, volcanic sandstone and conglomerate. These rocks belong to the Early and Middle Jurassic Ladner Group and are in unconformable and fault contact with greenstone, volcanic sandstone and gabbro assigned to the Lower Triassic Spider Peak Formation to the southwest and northeast, respectively. Thin, elongate units of brecciated, altered and strongly cleaved fault-bound slices of greenstone also occur within the Ladner Group. Ultramafic rocks of the Coquihalla serpentine belt occupy the East Hozameen fault to the north.
The Ladner Group sediments have all undergone a complex history of structural deformation characterized by folding. The unconformable contact between the Ladner Group and Spider Peak Formation is locally faulted and sheared.
Hostrocks at the McMaster prospect include mylonitic volcanics, fault-related serpentinite, serpentinite, quartz-albite-carbonate altered zone rock, chloritic greywacke, siltstone and argillaceous siltstone, tucidite-related greywacke, lithic wacke, pebble conglomerate, siltstone, and conglomeratic argillite.
The McMaster zone is similar in its mineralogy, alteration features, host rock lithologies and overall structural and stratigraphic setting to that at the Carolin mine (092HNW007). Early trenches exposed several discrete quartz-albite-carbonate alteration zones containing abundant pyrite, pyrrhotite and arsenopyrite within and adjacent to northwest striking bands of wacke interbedded with siltstone. The wacke bands are strongly albitized and chloritized, and form quartz-veined outcrops that weather to a black and rust-stained colour. The zones host up to 10 per cent sulphides together with both pervasive albite and albite veins and at least two generations of irregular, randomly oriented quartz veins. Late quartz-carbonate veins and carbonate disseminations are also present. Assays as high as 18.51 grams per tonne gold across 6.10 metres were obtained from these trenches (Assessment Report 19877, page ii).
In 1975, subsequent diamond drilling determined that the McMaster prospect is hosted in a series of thin fault wedges stacked on top of westerly dipping, post-mineralization shear zones related to the East Hozameen fault. Mineralized zones strike 320 to 340 degrees and dip 60 degrees to the northeast with several large westerly dipping shear zones striking 330 degrees and dipping 60 degrees to the northeast. Mineralized zones have been defined for 195 metres along strike and to a maximum of 40 metres downdip. They appear to be related to a serpentinite-filled structure (McMaster Pond fault), which occupies the small valley east of the McMaster mineralized zones. Shear motion appears to be right lateral, strike slip and in the order of 800 metres. The dip-slip component is presently unknown. Five main mineralized zones have been identified (zones A to E).
Zone A is exposed in the North trench and has been intersected in drillholes M-7, M-9 and M-13. It has a strike length of about 100 metres and is open to the south. A 4.3-metre chip sample from the North trench yielded 5.07 grams per tonne gold (Assessment Report 24035). A 2.09 metre interval between 0.91 and 3.00 metres from drillhole M-13 yielded 4.25 grams per tonne gold.
Zone B is exposed in Middle trench, from which a 2.53-metre chip sample yielded 4.66 grams per tonne gold (Assessment Report 24035). The zone has also been intersected in drillhole M-1. The zone has a known strike length of 40 metres and is also open to the south. The best drillhole intersection yielded 2.40 grams per tonne gold over 4.15 metres between 12.65 and 16.80 metres.
Zone C has yielded the highest grade and is exposed in the Middle and South trenches. Chip samples have yielded 12.00 grams per tonne over 6.59 metres and 9.15 grams per tonne over 2.93 metres from the Middle and South trenches, respectively. The zone was also intersected in drillholes M-2, M-3, M-10, M-11 and has a strike length of about 120 metres. Drillhole M-10 yielded 4.53 grams per tonne gold over the 3.77 metres interval between 7.48 and 19.85 metres.
Zone D, exposed in the South trench, has yielded 1.61 grams per tonne gold over 3.60 metres. The zone has also been intersected in drillhole M-6 and M-12 and has a strike length of about 100 metres. Drillhole M-12 yielded 5.21 grams per tonne gold over the 6.50 metre interval between 8.50 and 15.00 metres.
Zone E is exposed in the South trench and intersected in drillhole M-12. A trench sample over 6.10 metres yielded 4.73 grams per tonne gold and a 6.29-metre drill core interval yielded 5.21 grams per tonne gold, including 2.5 metres yielding 6.51 grams per tonne gold (Assessment Report 19877, page 14).
Four rock chip samples were taken from outcrops at the Lorraine showing of the south Pipestem area in 1986. These four samples yielded gold values ranging from 1.00 to 7.05 grams per tonne gold over 0.30 to 2.5 metres.
Pitable reserves at McMaster total 186,000 tonnes of 1.88 grams per tonne gold (CIM '97 Vancouver Program, April 27-30, 1997, page 81).