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Publication Date

2012

Document Type

Honors Project

Department

Geosciences

Keywords

Geology, Structural-Ontario-Grenville County, Rock deformation-Ontario-Grenville County, Orogeny-Ontario-Grenville County, Shear zones (Geology)-Ontario-Grenville County, Geology, Stratigraphic-Proterozoic, Structural geology, Ductile deformation, Mid-crust, Grenville orogeny, Proterozoic, Tectonics, Kinematics

Abstract

The Central Metasedimentary Belt (CMB, also called the Composite Arc 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. The Salerno Creek Deformation Zone (SCDZ) is a NE-SW-trending zone of grain-size-reduced and strained mostly meta-igneous rocks within the CMB and has been proposed as the boundary between the Bancroft Terrane and the Harvey-Cardiff Domain of the Elzevir Terrane. Previous work dates deformation between 1211.3±1.5 Ma and 1045.4±2.9 Ma. This study aims to refine the nature of motion along the SCDZ through analysis of macro- and micro-scale kinematic indicators. It is also the first kinematic study of the SCDZ, and one of few structural analyses in this portion of the CMB.Kinematic indicators observed in outcrop and thin section show a southeast-side-down shear sense, particularly in felsic lithology. However, mafic samples show both southeast-sideup and southeast-side-down shear sense indicators. These shear sense indicators reveal conflicting kinematics in the SCDZ compared to previous studies and within this study. 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 extensional reactivation during late orogenic collapse. This work also expands understanding of the architecture of ductile deformation within the crust, which can only be attained through study of exhumed ancient orogens.

Language

English

Comments

v, 55 p. : ill. (some col.), maps (some col.) Honors project-Smith College, Northampton, Mass., 2012. Includes bibliographical references (p. 39-43)

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