Deformed garnets in a mylonitic rock from the Grenville Front and their tectonic significance

Abstract

Garnet porphyroclasts in quartzo-feldspathic mylonitic rock from near Sudbury are described. They form oblate spheroids with an axis of symmetry normal to the mylonite foliation. Deformation of the porphyroclasts appears to have been tectonically controlled. There is no crystallographic preferred orientation, but where bend axes in the structure can be detected on Lane photographs, they consistently lie in the mylonitic foliation nearly normal to a prominent regional lineation (elongation of quartz and porphyroclastic feldspar grains). Consideration is given to the significance of the study in the interpretation of minor structures along the Grenville Front and other similar tectonic situations.