Geology of the Andrew Lake, South District, Alberta

The geology of a 72 square-mile area in the Precambrian Shield of northeastern Alberta is shown on a colored map of a scale of 2 inches to 1 mile. The western part of the area is underlain by granite gneiss containing isolated bands and patches of high-grade metasedimentary rocks, and the eastern part by a low-grade metasedimentary-volcanic complex associated with porphyroblastic biotite granites and with abundant massive biotite and leucocratic granites and pegmatites. Nineteen rock types are described with respect to hand specimen characteristics, field occurrence, contact relations, and chemical and modal analyses. Schistosity and foliation are well developed in most of the rock units, and small-scale folds and shear zones are common. A set of north to northwest trending faults is superimposed on the structural pattern, cutting across the prevailing northerly strike of the major rock units. Minor radioactive anomalies and evidence of mineralization were observed in relation to metasedimentary rocks and fault zones.