The region includes strata from the Purcell and Windermere supergroups, overlain by a Paleozoic platformal carbonate succession. The structure of the area is dominated by the Mount Forster-Steamboat fault, one of a series of Mesozoic thrust faults, and it carries folded Middle and Upper Proterozoic strata over folded Upper Proterozoic and Paleozoic strata.
In the Brisco occurrence area, the Upper Cambrian to Middle Ordovician McKay Group conformably overlies the Jubilee Formation and is unconformably overlain by the Upper Ordovician Beaverfoot Formation. The Middle-Upper Cambrian Jubilee Formation consists of a thick succession of massive to thin bedded dolomite and limestone. The McKay Group consists of recessively weathering shales, argillaceous limestone, thin sandstones and dolomitic biowackestones. The top few metres of the McKay Group are often hematite-stained reflecting possible subaerial exposure prior to the deposition of the overlying Beaverfoot Formation. The Middle Ordovician to Silurian Beaverfoot Formation rests unconformably on the McKay Group and on the Jubilee Formation. A white quartzite at the base of the Beaverfoot Formation is medium to thick bedded and usually massive and is overlain by a series of thick-bedded, massive biowackestones and peloidal mudstones with some beds of mature quartz pebble grits, limestone and dolomite. The top of the formation is eroded beneath the Middle Devonian Mount Forster Formation. Karst features, coarse recrystallization, silicification, breccias and base metal mineralization are developed adjacent to this unconformity.
At the Brisco quarries, barite had been exposed across an average width of 7.62 metres for 237.7 metres along a northerly striking breccia zone within dolomite of the Beaverfoot Formation. The host rocks have a north strike and steep dips, ranging from 77 degrees to vertical. The deposit is in the east limb of a syncline which is cut by numerous faults of varying magnitude. The west wallrock is highly fractured dark grey to black dolomite that is commonly brecciated with a few scattered lenses or horses of brown quartzite. Mountain leather is abundant as films on fracture surfaces and a few small barite veins are present. The east wallrock is light grey weathering buff to flesh-coloured dolomite and limestone. It is brecciated, and near the main barite body contains barite in the matrix. The orebody itself is brecciated. Much of the barite is white, but the white sections are irregularly shaped and are usually edged or cut by zones of variable width that consist of a fine-grained black matrix enclosing angular fragments of white barite a fraction of a centimetre to several centimetres in diameter. The black colour is due to carbon (graphite).
The barite pinches and swells both horizontally and vertically. To the north it appears to be cut off by a fault and it pinches out to the south. White barite, occurring as irregular masses forming the matrix around breccia fragments of light coloured dolomite, occurs 762 metres north of the main body. A small amount of barite, present as irregular discontinuous masses in a zone of shearing, occurs 550 metres to the south.
Drilling in 1980 at the south end of the main ore zone intersected only a few stringers of barite. Drilling to the east and northeast of the main zone indicated a potential for 3000 tonnes of barite with a specific gravity of 4.27.
Old workings indicate that the barite occurred in a steeply dipping horizon bounded to the east by a fault structure. The west contact appears to be both fault controlled and conformable with the host dolomite. The mined out zone appears to have been controlled by a northerly plunging structure.
Production from the Brisco operations began in 1952 and continued to 1980. Initial production was from an open pit. In subsequent years production came from underground operations. A total in excess of 133,000 tonnes of barite was produced during this time. The deposit is considered depleted but a modest reserve of barite, not economical, is still present (Butrenchuk, S.B.B., 1988)
The main deposit and quarrying operations are on the Salmon claim (Lot 15046).