CONFLICTING KINEMATICS OF THE SALERNO CREEK DEFORMATION ZONE, GRENVILLE PROVINCE, ONTARIO

The Composite Arc Belt (formerly Central Metasedimentary Belt) in the southern Ontario Grenville Province is part of a Proterozoic orogen exhumed from lower-crustal levels and hosts a series of southeast-dipping ductile shear zones (e.g. Carr et al., 2000; Hanmer et al., 2000). The Salerno Creek Deformation Zone (SCDZ) is a NE-SW-trending zone of grain-size-reduced and strained mostly meta-igneous rocks within the Composite Arc Belt and has been proposed as the boundary between the Bancroft “Terrane” and the Harvey Cardiff Domain of the Elzevir Terrane (Easton and Kamo, 2011; Easton and Carr, 2009). Previous work dates deformation between 1211.3±1.5 Ma and 1045.4±2.9 Ma (Easton and Carr, 2009). This study aims to refine the nature and timing of motion along the SCDZ using macro- and micro-scale kinematic indicators and monazite deformation geochronology.

Centimeter-scale kinematic indicators observed in the field and most porphyroclasts in thin section show an east-side-down shear sense. These shear sense indicators, associated with regional extension rather than terrane accretion, reveal conflicting kinematics in the SCDZ compared to previous studies (Easton and Kamo, 2011). While extensional sense of shear undermines the SCDZ’s candidacy for a terrane boundary, it does not rule out the possibility of a tectonic boundary that experienced late extension, which monazite dates could help elucidate.