Deformed sedimentary fabrics in metamorphic rocks: Evidence from the Point Lake area, Slave province, Northwest Territories

Abstract

The Point Lake orogenic belt in the Archean Slave province of Canada contains deformed metasedimentary rocks ranging from greenschist to granulite facies. At low grade, combinations of simple shear, pure shear, and initial lamina shape form a wide geometric variety of strained cross-laminae. At higher metamorphic grades, deformed sedimentary structures are recrystallized and in places included in porphyroblasts as internal foliations or inclusion trails. Different manifestations of deformed sedimentary layering produce textures resembling early-differentiated tectonic foliations. Recognition of the reorientation of sedimentary structures and their progressive incorporation into porphyroblasts greatly simplifies the structural history of the Slave province; previous models invoked as many as ten structural events to account for observed fabrics and inclusion trails, whereas the model presented herein requires only two.