Bulletin 029

Author(s) Date 1970-12-31

Rock salt (sodium chloride) deposits of commercial thickness and purity underlie a large area in east-central and northeastern Alberta, extending into extreme northwest parts of the province. The deposits form part of the Middle Devonian Elk Point Group which contains four mappable salt units caged (from oldest to youngest): lower Lotsberg, upper Lotsberg, Cold Lake and Prairie Evaporite Salts. All but the rairie Evaporite Salt lie wholly within the study area (east-central Alberta), although a separate deposit of Cold Lake Salt exists in orthern Alberta. The salt deposits attain a maximum aggregate thickness of nearly 1,400 feet in east-central Alberta, thinning gradually (depositionally) in all directions except northeast, where all of the deposits except the lower Lotsberg Salt are truncated due to post-depositional solution of the beds.

The thickest, most extensive salt units are the upper Lotsberg and Prairie Evaporite Salts, which exceed 500 and 700 feet at their espective depocenters. The younger and more shallow Prairie Evaporite Salt ranges in depth from 700 feet in the northeast part of the study area to 6,000 feet in the southwest. It is a 'normal', first-cycle, marine evaporite deposit containing a normal proportion of soluble and insoluble impurities interbedded with or dispersed within the alite beds. The upper Lotsberg Salt is from 600 to 1,000 feet deeper than the Prairie Evaporite Salt but is more favourable for industrial use owing to its superior chemical quality. Both the Lotsberg and Cold Lake Salt deposits have a complex history of solution and recrystallization, part of which occurred in non-marine waters, subsequently resulting in abnormally small amounts of impurities in the rock salt.

Within the Lotsberg and Cold Lake successions non-salt strata are rare; thus, solution-mining recoverability of the salt is greatly enhanced. Notably lacking are interbeds of anhydrite, reflected in SO4 concentrations commonly less than 0.1 weight per cent, about one enth of the amount considered normal for rock salt. Magnesium and otassium salt concentrations also are consistently very low, whereas in the Prairie Evaporite Salt they tend to increase towards the topof the deposit and also laterally southeastward.

Exploitation of the salt deposits in east-central Alberta has continued since 1938, with production in 1969 of more than 150,000 tons valued at $2.4 million. Increasing industrial development in Alberta undoubtedly will lead to increasing demand for salt, mainly to meet the expanding requirements of the chemical industry. Greater indirect use of salt beds for storage of liquefied petroleum gas LPG) and natural gas (in manmade caverns ) also is foreseen, and improved solution mining techniques may lead ultimately to magnesium nd bromine extraction through selective brining of beds rich in these elements.

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Hamilton, W.N. (1971): Salt in east-central Alberta; Research Council of Alberta, RCA/AGS Bulletin 29, 65 p.