The Hyde-Macraes shear zone in Otago: A result of continental extension or shortening? A kinematic analysis of the Footwall Fault

Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Geology
Degree name
Master of Science
Publisher
University of Canterbury. Geological Sciences
Journal Title
Journal ISSN
Volume Title
Language
Date
2007
Authors
Butz, Christoph Florian
Abstract

Mineralised shear zones in Otago are often truncated by regional low-angle faults, which juxtapose schist of different metamorphic grade. The Footwall Fault and the Hyde-Macraes Shear Zone are one example for this kind of tectonic setting, and are the subject to this study. Although, the mechanisms for the development of the mineralised thrust-origin shear zones are well studied, the relationship to the truncating faults is still poorly understood. Currently, the truncating low-angle faults are assumed to be related to crustal extension, starting in the early Cretaceous after the schist passed the ductile-brittle transition. This study presents new kinematic data for the Footwall Fault, suggesting development of normal sense movement under ductile conditions due to an abundant shear band cleavage in the footwall, which dynamically recrystallises quartz grains. However, brittle high-angle normal faults truncating these shear bands indicate either reactivation of normal sense movement after passing the ductile-brittle transition or continuous normal sense movement during the transition. Furthermore, this study presents a model, which suggests a regional scale rolling hinge development, consisting of an array of individual low-angle normal faults along the boundary of the textural zone change from TZ IV to TZIII, and strike-parallel high-angle faults at the NE margin of the Otago schist.

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Citation
Keywords
Hyde-Macraes Shear Zone, Footwall Fault, Otago Schist
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
Rights
Copyright Christoph Florian Butz