The Aisla East occurrence is located along a creek flowing east out of Aisla Lake, approximately 2.4 kilometres northwest of Mount McKay.
Regionally, the area is underlain by siltstones, quartzites and phyllites of the Proterozoic Upper Aldridge and Lower Creston formations (Purcell Supergroup), intruded by a small quartz monzonite stock, possibly Cretaceous. The Lower Creston Formation consists mainly of laminated to thickly bedded argillites and siltites with minor fine-grained quartz wackes. The rocks are waxy green to olive in colour with tan-weathering surfaces, wavy bedding and abundant mudcracks. Rocks of the Upper Aldridge, underlying an area to the east consist of a relatively homogeneous unit with occasional thin interbeds of light grey quartzite and laminated light and dark grey argillaceous quartzite. The intrusive stock consists of medium- to fine-grained massive biotite monzogranite. The sediments adjacent to the intrusion have been altered to produce concentric zones of biotite hornfels and siliceous siltstone.
Locally, sericite-altered quartzites host mineralized fracture sets crosscutting bedding and striking 050 degrees with a dip of 64 degrees northwest. The fractures contain disseminated galena, sphalerite, chalcopyrite, arsenopyrite and pyrite. Sulphide-rich quartz veins and zones of intense albitic brecciation hosting sphalerite and galena are also reported.
In 2005, rock samples (MAL-16 to -19) from the occurrence area yielded values from trace to 0.08 per cent molybdenum, 0.05 to 0.17 per cent lead, 0.03 to greater than 1.00 per cent zinc, trace to 0.03 per cent cadmium, 0.01 to 0.06 per cent bismuth, 0.006 to greater than 0.010 per cent tungsten and 14.4 to 59.5 grams per tonne silver, and a sample (MAL-4) of limonite- and carbonate-altered quartz vein, taken several hundred metres to the southeast, yielded 0.11 per cent bismuth and 87 grams per tonne silver (Assessment Report 28323).
Work History
The area has been explored in conjunction with the nearby Aisla (MINFILE 082FNE001) occurrence, and a complete exploration history of the area can be found there.
