Structural Analysis of the Amisk and Missi Rocks North of Amisk Lake, Saskatchewan

Abstract

Volcanic, sedimentary and intrusive rocks of Precambrian age in the southwestern part of the Churchill Province of the Canadian Shield just west of Flin Flon, Manitoba have a complex structural pattern as the result of three superposed phases of deformation. All rocks have.undergone lower greenschist facies metamorphism. The first phase of deformation (P2) is the most pronounced and consists of a large isoclinal syncline with a regionally developed axial-plane foliation (S2). The second phase (P3) resulted in the development of three faults, two major folds, and an array of minor structures which include numerous minor folds, fracture and crenulation cleavages (S3), and minor faults. The last phase (P4) is represented by a large open fold that caused a distinct strike swing of bedding, S2, folliation, am major faults. Pebbles in the meta-conglomerate and meta-sandstone of the Missi Group show a variety of deformational textures which have been interpreted as resulting from a combination of intracrystalline and intergranular flow processes. Their interpretation also indicates a progressive decrease in the ductile behaviour of the rocks from the P2 to the P3 phase.