Middle to lower crustal shear zone processes in collisional orogens
department or school: Science, Irving K. Barber Faculty of (Okanagan)
department or school: Earth, Environmental and Geographic Sciences, Department of (Okanagan)
data provider: DSpace
degree campus: UBCO
creator: Graziani, Riccardo
issued: 2021-08-31T18:06:59Z
issued: 2021
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: Despite the major role played by shear zones in large-scale deformation accommodation processes across structural levels, the present record of such structures from the lower crust is limited because of sparse exposure of such rocks on Earth. Significant gaps, therefore, remain in our knowledge about the deformation processes and behavior of lower crustal shear zones during collision. This contribution aims to fill that gap by studying the dynamics of the continental lower crust at both the micro and regional scale and by developing new methods for studying the tectonic evolution of lower crustal terranes. Using the tilt angle (β) of a quartz crystallographic preferred orientation (CPO) and the orientation of the C′ shear bands (θ) it was possible to develop a new technique for quantifying the sectional vorticity number (Wₙ) in medium to high-metamorphic grade deformation environments typical of deep crustal levels. This vorticity number estimation technique, named the C′-c method, can be applied using the following formula: Wₙ = Cos[2(θ-β)]. Microstructural and quartz CPO analyses of the lower crustal Intra Tantato shear zone (ITSZ; East Athabasca Mylonite Triangle of northern Saskatchewan, Canada) reveals that specimens with few hydrated mineral phases deformed mainly by dislocation creep and dynamic recrystallization. In contrast, in specimens rich in hydrated mineral phases, deformation was dominated by pressure solution and (re)precipitation processes that enhanced phase mixing and promoted grain boundary sliding. These results indicate a strong mineralogical and fluid control on deformation and potential strain softening processes in the lower crust. Finally, quartz CPO analysis combined with garnet Lu/Hf and Monazite U/Pb geochronology were used to reconstruct the history of the ITSZ as a major thrust structure that was active at 1904 ± 19 Ma and resulted in nappe stacking within the continental lower crust. Microstructural and geochronological data also outl…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/79541
note: MIDDLE TO LOWER CRUSTAL SHEAR ZONE PROCESSES IN COLLISIONAL OROGENS By Riccardo Graziani Ms.C., University of Pisa, 2017 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY In THE COLLEGE OF GRADUATE STUDIES (Earth and Environmental Sciences) THE UNIVERSITY OF BRITISH COLUMBIA (Okanagan) August 2021 © Riccardo Graziani, 2021 ii The following individuals certify that they have read, and recommend to the College of Graduate Studies for acceptance, a thesis/dissertation entitled: Middle to Lower Crustal Shear Zone Processes in Orogens Through Time submitted by Riccardo Graziani in partial fulfillment of the requirements of the degree of Doctor of Philosophy . Dr. Kyle Larson, I. K. Barber School of Arts and Sciences, UBC Okanagan Supervisor Dr. John Greenough, I. K. Barber School of Arts and Sciences, UBC Okanagan Supervisory Committee Member Dr. Lori Kennedy, Department of Earth, Ocean and Atmospheric Sciences, UBC Vancouver Supervisory Committee Member Dr. Joel Saylor, Department of Earth, Ocean and Atmospheric Sciences, UBC Vancouver University Examiner Dr. Joseph White, Department of Earth Sciences, University of New Brunswick External Examiner iii Abstract Despite the major role played by shear zones in large-scale deformation accommodation processes across structural levels, the present record of such structures from the lower crust is limited because of sparse exposure of such rocks on Earth. Significant gaps, therefore, remain in our knowledge about the deformation processes and behavior of lower crustal shear zones during collision. This contribution aims to fill that gap by studying the dynamics of the continental lower crust at both the micro and regional scale and by developing new methods for studying the tectonic evolution of lower crustal terranes. Using the tilt angle (β) of a quartz crystallographic preferred orientation (CPO) and the orientation of the C′ shear bands (θ) it was possible to develop a new…
has type: Thesis/Dissertation
date issued: 2021-09
is shown at: 10.14288/1.0401816
language: eng
degree discipline: Earth and Environmental Sciences
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
contributor: Larson, Kyle
type: Text
identifier URI: http://hdl.handle.net/2429/79541