The Delamerian Orogen- An overview of the resistivity structure across scales

Here we present 3D and 2D resistivity models of the lithosphere beneath an area of southeast Australia, derived from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) and a subsequent infill broadband MT transect collected in October 2020. The Flinders Ranges, South Australia is a zone that has been weakened by multiple Precambrian rift cycles related to the breakup of Rodinia. These rift cycles have possibly led to the utilization of this lithosphere for the focussing of fluid alteration causing high conductivities in crust and upper mantle depths in this region, as imaged in the AusLAMP 3D resistivity models. The northwestern end of a 100 km MT transect traverses this region and 1.5 km MT site spacing resolves high conductivity pathways that broadly correlate with previously identified mineral prospects. These pathways straddle the resistive granodiorite rocks of the Anabama pluton, known to host porphyry-style mineralisation. To the southeast, the transect images the onlapping Mesozoic Murray Basin sediments, and Cambrian rocks beneath, where the crust exhibits high resistivities and seismic velocities, suggesting a depleted lithosphere.