Multidimensional magnetotelluric studies of the Precambrian Alberta basement

• Author / Creator

  Wang, Enci

• The Alberta basement is part of the North American craton, which has been stable since Proterozoic and is also known as Laurentia. Geophysical and geology studies in Alberta have revealed that the basement rocks of Alberta have been assembled by complex tectonic events, such as subduction, arc-continent and continent-continent collisions accompanied by magmatism, metamorphism, metasomatism, and strike-slip deformation. Study of the Alberta basement provides information on how tectonic processes operated in the past and how they affect the current crustal and lithospheric structure. The magnetotelluric method has been used to study lithospheric structure in many areas of the world. This thesis describes the first detailed 3-D study of the Alberta basement using MT. The thesis has been divided into two projects. In Project 1, broadband magnetotelluric data were collected in northwest Alberta and were used to generate a 2-D electrical resistivity model of the crust across the Hay River Fault. In Project 2, long-period MT data collected in central Alberta were combined with legacy long-period MT data and were used to generate the first 3-D electrical resistivity model of the crust and upper mantle beneath Alberta. In Project 1, The Western Canada Sedimentary Basin was imaged as a low resistivity layer above the resistive crystalline basement. Four crustal basement conductors were defined: (1) the Kiskatinaw conductor, (2) a conductor on the boundary of the Ksituan and Chinchaga domains, (3) a conductor on the boundary of the Chinchaga and Buffalo Head domains and (4) a conductor near the Hay River Fault. Both (1) and (2) correspond to areas of high seismic reflectivity. The low resistivity can be explained by the presence of interconnected grain boundary graphite, or sulfide minerals, deposited by metamorphic fluid migration. In Project 2, The Western Canada Sedimentary Basin was imaged as a low resistivity layer. A number of crustal and upper mantle conductors were imaged and include: (1) the Red Deer conductor, (2) the Kiskatinaw conductor, (3) a conductor coincident with the Kimiwan oxygen isotope anomaly, (4) the southern Alberta – British Columbia conductor, (5) the Loverna block conductor, (6) a conductor beneath the Birch Mountain kimberlite field. All these conductors can be related to past tectonic events suggested by previous studies. The lithosphere-asthenosphere depth across Alberta was defined from the electrical resistivity structure, and varies from 150 – 300 km. The Snowbird tectonic zone in Alberta is characterized by a deep and resistive lithosphere which indicates that it is highly depleted in incompatible elements. The diamondiferous Buffalo Head Hills kimberlite field is believed to be underlain by the most depleted lithosphere in Alberta.

• Subjects / Keywords

  • Precambrian
  • Alberta basement
  • Magnetotelluric study

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-sctk-1z12

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.