Characterization of the Nature of Deformation and Metamorphic Gradient Across the Grenville Front Tectonic Zone in Carlyle Township, Ontario

Abstract

<p> The last major episode of deformation occurred in the area studied during the Grenville orogeny (~1000 Ma ago). Deformation of this zone is characterized by a northeast trending penetrative foliation and southeast plunging mineral lineation which increase in intensity and decrease in inclination from northwest to southeast. The deformation was imposed during reverse fault movement in which the southeastern block (the Grenville province) was vertically displaced on the order of 20 kilometers above the adjacent block (the Southern province). The Killarney belt of granites, which separate the Grenville province from the Southern province in this area, are intrusive into the Huronian metasediments and predate the Grenville orogeny. These granites also show evidence of Grenvillian deformation. </p> <p> Paleopiezometry has shown that the differential stress during deformation increases from less than 1 Kbar to more than 6 Kbar from southeast to northwest. The microstructural strain features in quartz and felspar and the mineralogy indicate that a temperature change o£ 400 C is associated with this change in differential stress. Kinematic analysis of mylonites supports the reverse fault model o£ the Grenville Front. </p>