Salt and gypsum in Alberta

CIM Bulletin, Vol. 75, No. 846, 1982

W.N. HAMILTON, Alberta Geological Survey, Alberta Research Council, Edmonton, Alberta

Evaporites abound in the Western Canada sedimentary basin, recurring throughout the stratigraphic column and widely scattered over the basin region. Alberta, situated centrally over the basin, includes many of the evaporites within its borders, but only a few have the right geological conditions to form potential economic deposits of salt or gypsum. These include the Middle Devonian Elk Point Group and related evaporites, Upper Devonian Wabamun Group—Palliser Formation evaporites, and evaporites of the Triassic Charlie Lake and Whitehorse formations.Salt deposits underlie almost half of Alberta. The major deposits belong to the Elk Point Group, which includes thick salt units in the Lotsberg, Cold Lake and Prairie Evaporite formations. Another, younger salt deposit in the Wabamun Group has only local distribution. Elk Point salts have a maximum aggregate thickness of 430 m in east-central Alberta. The deposits deepen southwestward across the province, from minimum depths of 210 m at Fort McMurray to 1820 m at Edmonton.The thickest, most extensive salt deposits are the upper Lotsberg and Prairie Evaporite salts. Both have excellent development potential. The upper Lotsberg is up to 150 m thick, consists of clear, very coarse crystalline halite with only minor impurities, and has a notable lack of non-salt strata in its succession. Analytical data for the Lotsberg Salt show extraordinary chemical purity. Prairie Evaporite Salt differs lithologically from the Lotsberg in having a significant non-salt component. The deposit is up to 200 m thick and consists of medium crystalline halite, brownish coloured and cloudy as a result of finely dispersed impurities. The main impurities—shale, anhydrite and dolomite—are most prevalent as interbeds in the salt succession, ranging from very thin laminae to beds several metres thick. Although of lesser purity, the Prairie Evaporite Salt is shallower, thicker and more extensive than the Lotsberg and the salt quality is quite acceptable for most industrial uses.Gypsum deposits known to exist in Alberta are undeveloped owing to their remote or restricted locations or their difficult accessibility. Middle Devonian (Elk Point Group or equivalent) deposits include the Kananaskis deposit in the Rocky Mountains of southwestern Alberta, and the Salt River and Fort McMurray deposits in northeastern Alberta. Closely related stratigraphically is the Peace Point deposit in northeastern Alberta, also Middle Devonian in age, but younger than Elk Point. The Head Creek deposit in southwestern Alberta is in the Upper Devonian Palliser Formation. The Fetherstonehaugh Creek and Mowitch Creek deposits, both in the west-central Alberta mountains, belong to the Triassic Whitehorse Formation.The Peace Point and Fort McMurray deposits have the best gypsum development potential for Alberta. The Peace Point deposit has excellent quality, with average grades running 95 per cent gypsum over thicknesses of 5 to 10 m, and reserves estimated in the order of 1 billion tonnes. Its National Park location does not rule out development, for the deposit lies on lands under negotiation as part of Indian land claims in northern Alberta. The Fort McMurray deposit on the Athabasca River is less remote than Peace Point (nearer to the Fort McMurray railhead), but is of somewhat lower grade and would require underground mining. Development of either deposit likely would have to await the industrialization concomitant with further oil sands development in this region.
Keywords: Industrial minerals, Alberta, Salt, Gypsum, Evaporites, Elk Point Group, Fort Vermilion Formation, Burnais Formation, Wabamun Group, Palliser Formation, Charlie Lake Formation, Whitehorse Formation, Lotsberg Salt, Cold Lake Salt, Prairie Evaporite Salt, Stettler Salt, Kananaskis Gypsum, Salt River Gypsum, Fort McMurray Gypsum, Peace Point Gypsum, Head Creek Gypsum, Featherstonehaugh Creek Gypsum, Mowitch Creek Gypsum.