Magnetotelluric constraints on the tectonic setting of Grenville-aged orogenesis in central Australia

摘要

Magnetotelluric (MT) data were collected over a 480 km long profile in central Australia, extending from the Mesoarchaean-Palaeoproterozoic Gawler Craton into the Mesoproterozoic-Neoproterozoic Musgrave Province. The two regions have contrasting geological histories and many reconstruction models of Proterozoic Australia propose that they were juxtaposed during the Mesoproterozoic. Despite the significant differences in geological background between the Gawler Craton and the Musgrave Province, the MT data did not image an electrical structure, or any change in electrical character, between them. MT models suggest that southern-central Australia is electrically separated into two parts. The first, comprising the northernmost Gawler Craton and the Musgrave Province, has a 5 km thick layer of moderate resistivity overlying highly resistive crust. The second, comprising the central-northern Gawler Craton, displays moderate resistivity to the base of the crust. The lithospheric mantle underlying both electrical regions is uniformly highly resistive. Our results suggest that the Musgrave Province and Gawler Craton are more closely related than is currently recognized. We propose that the Gawler Craton forms basement to the Musgrave Province and that the Grenvillian Musgrave Orogeny was an intracratonic reworking event that overprinted the older basement.