The Sisters Copper occurrence is located at an elevation of approximately 700 metres on a northeast-facing slope, southwest of the Adam River and approximately 2.8 kilometres southwest of the west end of Keta Lake.

The area to the west of the Adam River is mainly underlain mainly by the upper part of the Upper Triassic Karmutsen Formation, comprising mainly thick massive flows with local intercalations of amygdaloidal basalt and pods of autoclastic breccias, pillowed and massive flows with thin intercalations of volcaniclastic and limy sandstones, all cut by thin dolerite/gabbro sills.

Locally, a 20-metre-wide zone hosts malachite, chalcopyrite and bornite on thin shears and fractures associated with three main parallel mineralized shear zones. At the core of the mineralized zone, a 1-metre-wide anastomosing shear zone, dipping 70 degrees and striking 185 degrees, is strongly silicified and contains irregular semi-massive bornite veins and stringers with abundant malachite in vuggy veins. The wallrock around the shear zone hosts 2 to 10 per cent disseminated bornite. A secondary bornite quartz vein is located 1 metre east of the main shear/vein and dips 66 degrees along a 160-degree strike. These orientations are reported to support a sinistral sense during emplacement of the veins. On the southwest side, copper mineralization is bounded from unmineralized basalt to the south by a steep shear zone dipping 73 degrees and striking 175 degrees. The southwest shear anastomoses between 20 to 75 centimetres wide with minor malachite and bornite mineralization along veinlets and disseminated in wallrock. A third shear zone/fault occurs 5 metres northeast of the main vein. This fault dips 76 to 74 degrees with a strike of 174 to 185 degrees and preserves intense shearing with associated bornite and malachite along the southwest side over 15 centimetres in width.

An associated and parallel zone of mineralization is located approximately 100 metres north of the main Sister Copper occurrence and has been traced intermittently along strike for approximately 1.2 kilometres to the northwest. The zone consists of copper mineralization within and along shallow veins and within amygdules in an epidote-quartz–altered basalt. The veins sets are shallow dipping and comprise dominantly quartz-potassium feldspar±epidote with bornite-chalcopyrite-malachite. Local steep fault sets are also mineralized.

In 2020, 10 grab samples (27321-27328, 27476 and 27477) from the main occurrence area yielded from 1.36 to 46.4 per cent copper, 2.7 to 144 grams per tonne silver and 0.020 to 0.751 gram per tonne gold, whereas 12 samples (27302-27308 and 27468-27472) taken from a parallel zone of mineralization, located approximately 400 to 600 metres to the northwest of the main zone, yielded from 0.127 to 11.700 per cent copper, 0.6 to 37.5 grams per tonne silver and trace to 2.52 grams per tonne gold (Assessment Report 39283).

Work History

The area has been explored in conjunction with the nearby Adam West (MINFILE 092L 222) occurrence and a completed regional exploration history can be found there. The occurrence was discovered in 2020.