Proterozoic tectonothermal processes imaged with magnetotellurics and
seismic reflection in southern Australia
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Abstract
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 2D 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-located
2D 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.
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