Preliminary Map 46 describes the geology of the Munroe-Alpine-Boivin carbonate-hosted lead-zinc occurrences in the Rocky Mountain Front Ranges (82J/3E) in southeastern British Columbia. The 1:25 000 scale geology map includes a legend, descriptive notes, 1:10 000 scale insert maps for each of the three occurrences, and three cross sections.
The Paleozoic and/or younger rocks comprise the Bull River amygdaloid. Upper Cambrian and Lower Ordovician McKay Group rocks are mainly shale and limestone. Lower and Middle Ordovician strata consist of shale, siltstone, argillaceous limestone and sandstone of the Glenogle Formation, and sandstone of the Tipperary Formation. Middle Ordovician to Lower Silurian Skoki Formation rocks are mainly limestone and dolomite, the Mount Wilson Formation consists of quartzite, and the Beaverfoot Formation is made up of cliff forming dolomite and limestone. Middle and/or Upper Devonian strata of the ‘Basal Devonian Unit’ include dolomite, mudstone, sandstone, conglomerate and gypsum. Upper Devonian rocks include strata of the Fairholme Group, the Alexo Formation, and the Palliser Formation. Fairholme strata include argillaceous limestone with lesser dolomite and mudstone. Alexo Formation units are mainly sandstone, dolomitic sandstone, dolomitic siltstone; and mainly thinly interbedded dolomite and limestone. Palliser Formation is subdivided into two members: the Morro Member has a basal limestone with dolomitic mottling unit, a limestone and argillaceous limestone unit, a dolomite unit, a dolomite unit with fenestral porosity (has associated zinc mineralization), and a unit of limestone with dolomite mottling. The Costigan Member has a lower unit of interbedded dolomite and limestone, and an upper unit of thinly interbedded dolomite and limestone. Mississippian strata are represented by the Exshaw Formation, with mainly shale and limy shale, the Banff Formation, with a lower unit of mainly shale, limestone, argillaceous limestone and chert, and an upper unit dominated by limestone, the Livingston Formation, with mainly limestone, the Mount Head Formation, with limestone and argillaceous limestone, and the Etherington Formation, with limestone, dolomite and siltstone. Pennsylvanian and Permian strata are quartz sandstone, dolomitic sandstone, silty dolomite, chert, and phosphorite of the Rocky Mountain Group.
Stratabound zinc mineralization is confined to the Lower Morro Member of the Upper Devonian Palliser Formation. The distinctive dolomite host has fenestral porosity developed and sparry white dolomite. Zinc mineralization post-dates the sparry dolomite. It occurs as disseminations and pods. The area may also have potential for the industrial minerals phosphorous and gypsum. The Munroe, Alpine and Boivin showings are all on the inverted limb of a major eastward verging anticline. The folded strata are also cut by a series of steep west dipping normal and listric normal faults. West of the Alpine occurrence the fold is truncated by a moderately dipping thrust fault.