Proterozoic tectonothermal processes imaged with magnetotellurics and seismic reflection in southern Australia

Over the last two decades,co-located seismic and magnetotelluric(MT) profiles provided fundamental geophysical data sets to image the Australian crust.Despite their complimentary nature,the data are processed and often interpreted separately without common processes in mind.We here qualitatively compare 2 D resistivity inversion models derived from MT and seismic reflection profiles across a region of Archean-Proterozoic Australia to address the causes of variations in seismic response and anomalous conductivity in the crust.We find that there exists a spatial association between regions of low reflectivity in seismic sections and low resistivity in co-located2 D MT modelled sections.These relationships elucidate possible signatures of past magmatic and fluid-related events.Depending on their diffuse or discrete character,we hypothesize these signatures signify fossil melting of the crust due to mafic underplating,magma movement or hydrothermal fluid flow through the crust.The approach discussed herein is a process-oriented approach to interpretation of geophysical images and a significant extension to traditional geophysical methods which are primarily sensitive to a singular bulk rock property or state.