The Benagerie Shear Zone: 1100 Myr of reactivation history and control over continental lithospheric deformation |
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| Authors: | H.A. Williams P.G. Betts |
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| Affiliation: | 1. Centre for Tectonics, Resources and Exploration (TRaX), School of Earth and Environmental Sciences, University of Adelaide, Adelaide SA 5005, Australia;2. Primary Industries and Resources of South Australia, 101 Grenfell Street, Adelaide SA 5001, Australia;3. Centre for Mineral Exploration Under Cover, School of Earth and Environmental Sciences, University of Adelaide, Adelaide SA 5005, Australia;4. Geotechnology, Department of Technology, Khon Kaen University, Thailand;1. Department of Geological and Atmospheric Sciences, 253 Science Hall, Iowa State University, Ames, IA 50011-1027, USA;2. U.S. Geological Survey, Denver Federal Center, Denver, CO 80225, USA;3. 23 Windsor Street, Fullarton 5063, South Australia, Australia;4. Robust Resources, Level 34, Gateway Building, 1 Macquarie Place, Sydney, New South Wales 2000, Australia;1. Ottawa-Carleton Geoscience Centre, Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada;2. Department of Earth Sciences, University of Toronto, Toronto, ON M5S 3B1, Canada;3. Department of Geology, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden;4. Faculty of Geology and Geography, Tomsk State University, Tomsk 634050, Russia;5. Division of Earth Sciences, National Science Foundation, Alexandria, VA 22314, United States;6. Geological Survey of South Australia, GPO Box 320, Adelaide, SA 5000, Australia.;7. Department of Earth Sciences, School of Physical Sciences, University of Adelaide, SA 5005, Australia.;8. Department of Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada |
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| Abstract: | A newly identified northwest–southeast oriented, deeply-rooted, steep to vertical, large-scale structural system within the Proterozoic Curnamona Province, Australia, which we term the “Benagerie Shear Zone”, is imaged in regional magnetic and gravity datasets. In this study, we use a combination of field analysis and quantitative geophysical methods, to establish a 1100 Myr history of activity along the Benagerie Shear Zone during which the location of younger geological structures are influenced by the pre-existing shear zone. This deformational system is interpreted to have 1) aided ascent and emplacement of the ca. 1600 Ma Ninnerie (magmatic) Supersuite; 2) controlled the loci of nucleation of normal faults during rifting and continental breakup at ca. 800 Ma; and 3) influenced the development of fold structures as well as acting as a plane co-linear to the rotation axis of pre-existing normal faults such that they were steepened and reactivated as strike slip structures during the ca. 500 Ma Delamerian Orogeny. We interpret that the Benagerie Shear Zone has not undergone uni-directional propagation during its evolution but rather through reactivation was a primary influence on controlling the nucleation of Neoproterozoic rift faults, thereby playing a major role in accommodating strain over a significant period of the evolution of the Curnamona Province. This study demonstrates that crustal-scale shear zones can evolve over hundreds of millions of years, have strike-lengths of hundreds to thousands of kilometers, and have vastly different surface expressions along strike. |
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