The SG occurrence consists of minor copper mineralization in quartz monzonite and granodiorite intrusions. It is located 700 metres east of the Southgate River, 23 kilometres west-southwest of the southern end of Chilko Lake.
The area is within a large biotite-hornblende granodiorite intrusion of the Late Cretaceous to Paleocene Bendor Suite. Within this intrusion is a small stock of paler, more felsic quartz monzonite to biotite granodiorite, forming an elliptical outcrop ranging from 2100 to 1500 metres in diameter, slightly elongate north-south (Assessment Report 3272). The contact between the two igneous phases is quite sharp, not marked by chilling, brecciation or local alteration. They are probably similar in age.
A broad area of alteration overlaps the eastern half of the quartz monzonite stock and the adjacent granodiorite host (Assessment Report 3272). It is mainly fracture-controlled, there being a prominent set of east-striking, moderately north-dipping fractures in this area. The alteration consists of silicification, sericitization, and epidotization, in order of degree. The fractures are commonly filled with white quartz, and range from 0.5 to 1.0 centimetre in thickness, spaced a few tens of centimetres apart.
The fractures are mineralized with sparsely disseminated chalcopyrite and bornite, locally accompanied by secondary sericite, potassium feldspar, epidote and rare magnetite. Pyrite is conspicuous by its absence. Other, minor sets of fractures trending northeast or northwest also contain chalcopyrite and bornite. In summary, the mineralization is relatively widespread, but very low grade.
In 1967, the Minister of Mines Annual Report for 1967 stated that Rio Tinto Canadian Exploration staked 10 S.G. claims in the vicinity of the ground later held by Swiss Aluminium Mining Co. of Canada Ltd. Geology of the claims were mapped and silt samples were collected from various creeks. These claims were allowed to lapse.
In 1970, prospecting in the Southgate River Valley for Swiss Aluminium Mining revealed low grade copper mineralization in north-dipping fractures in a granodiorite host rock exposed in outcrops for 1500 metres along a road. The 64 claim block Sam claims were staked.
In 1971, the Swiss Aluminium Mining Co. of Canada Ltd. conducted work on their Sam 1-64 claim. The property was mapped during 1971 at a scale of 1 inch to 400 feet. Three reconnaissance soil sample lines were run in a north-south direction. In the area where copper mineralization was observed, 43 samples averaged 140 parts per million copper. Outside this area, 34 soil samples averaged 49 parts per million copper. Rock chip sample ranged from 8 to 570 parts per million copper (Assessment Report 3272).
