The Wollaston Lake fold-belt system, Saskatchewan–Manitoba

Abstract

The Wollaston Lake fold-belt system, a major feature of the Churchill (structural) Province, consists of coalescing fold belts that collectively have been traced for about 400 miles. The fold belts, formed during the Hudsonian orogeny ~1750 million years ago, consist of tightly to isoclinally folded metamorphic and migmatitic rocks. They are bounded mainly by granitic rocks (in the broad sense) that are probably in part younger and in part older. The metamorphic rocks comprising them have been assigned locally to the Daly Lake, Sandfly Lake, or Meyers Lake Groups. The Daly Lake Group (a miogeosynclinal type of assemblage) has an uncertain relationship to the Sandfly Lake Group (eugeosynclinal assemblage); it was probably not deposited contemporaneously with the Meyers Lake Group. The Meyers Lake Group, which has a considerable resemblance to 'stable shelf1 assemblages, although it is less mature, overlies the Sandfly Lake Group, probably unconformably. Metamorphic rocks lithologically similar to those assigned to the Daly Lake Group form most of the fold-belt system. Rocks similar to those assigned to the other groups are of limited extent. The rocks within the fold-belt system have undergone regional metamorphism of the andalusite–sillimanite or low pressure intermediate type and in general now belong to the amphibolite facies. Mineralization within the fold-belt system, consisting of syngenetic (?) sphalerite, galena, and copper minerals, was widespread, but is not yet known to be of economic importance. The most prominent zone of magnetic anomalies in the Precambrian of Saskatchewan coincides in part with the fold-belt system.