Timing of deformation and exhumation across the Karari Shear Zone,north-western Gawler Craton,South Australia |
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| Authors: | G Fraser A Reid R Stern |
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| Institution: | 1. Minerals and Natural Hazards Division , Geoscience Australia , GPO Box 378, Canberra , ACT 2601, Australia geoff.fraser@ga.gov.au;3. Geological Survey of South Australia , Department for Manufacturing, Innovation, Trade, Resources and Energy, South Australia, GPO Box 1264 , Adelaide , S.A , 5001 , Australia;4. Canadian Centre for Isotopic Microanalysis , Department of Earth and Atmospheric Sciences, 1–26 Earth Sciences Building, University of Alberta , Edmonton , T6G 2E3 , Canada |
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| Abstract: | In the north-western Gawler Craton of South Australia, the Karari Shear Zone defines a boundary between late-Archean to earliest Paleoproterozoic rocks, which have remained largely undisturbed since the earliest Paleoproterozoic, and younger Paleoproterozoic rocks that have been reworked through multiple late Paleoproterozoic and Mesoproterozoic metamorphic and deformation events. The history of movement across the Karari Shear Zone has been investigated via new U–Pb and 40Ar/39Ar geochronology, in combination with pre-existing geochronological and metamorphic constraints, as well as the structural geometry revealed by a recently acquired reflection seismic transect. The available data suggest a complex history of shear-zone movement in at least four stages, with contrasting sense of motion at different times. The first period of movement across the Karari Shear Zone is inferred to have been a period of extension at ca 1750–1720 Ma. This was likely closely followed by reactivation during the Kimban Orogeny between ca 1720 and 1680 Ma, although the sense of movement during this period is unclear. Further reactivation, in a thrust sense, occurred between ca 1580 and 1560 Ma, resulting in significant exhumation of marginal domains of the Gawler Craton to the north of the Karari Shear Zone. A final episode of largely strike-slip shear-zone movement occurred at ca 1450 Ma. |
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| Keywords: | Gawler Craton geochronology shear-zone reactivation exhumation Proterozoic tectonics |
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