ABSTRACT

The Cominco Fertilizers Limited mine, near the southeastern edge of the Elk Point Basin, has been in operation for 25 years. During that time a number of geological features have been encountered which help in understanding the genesis of the Prairie Evaporite (Devonian). Many of the primary features, which provide an excellent insight into the conditions which existed at the time of deposition, can be related to modern features observed on the mill tailings areas. Secondary features often represent a major disruption to mining activities where dissolution of the deeper salt has caused collapse of the ore beds and overlying Devonian Dawson Bay limestone. There is evidence that these secondary features have a deep seated tectonic control which can often have a surface expression. A minor brine inflow has been experienced at the mine for several years. The mechanisms which created the collapse features can be compared to the current processes observed at the inflow site. Potash mines are operating at depths where the overburden load is greater than the strength properties of the evaporite rock and therefore are subject to large amounts of room closure. The healing process which sealed up these collapse features can also be seen in the closure of mine openings.