Two near-orthogonal magnetotelluric (MT) traverses were conducted across the eastern part of the Capricorn Orogen. The results show distinct variations in mantle and crustal electrical conductivity across the Orogen. They are interpreted to represent a series of discrete tectonic blocks separated by crustal-scale faults or shear zones, which dip towards the centre of the Orogen. By contrast, in the western part of the Orogen, the major structures consistently dip towards the south.
The 2011 MT survey of the East Capricorn Orogen has indicated the Yilgarn and Pilbara Cratons are resistive and separated by a large volume of conductive crust in the middle of the Orogen. Although the nature and origin of this crust is not known, it is interpreted as Proterozoic crust analogous to the Glenburgh Terrane in the western part of the Orogen. Therefore, the Pilbara and Yilgarn Cratons do not appear in direct contact with each other in this part of the Orogen.
The present-day crustal architecture, as imaged in this survey (see image below), is a reflection of processes imparted late in the crustal thickening cycle. As such, any major structural differences across the Orogen likely reflect complex collisional processes, rather than any fundamental differences in the pre-collisional architecture — such as subduction polarity or the location and distribution of island arcs.
All MT data are now available for download from the Airborne Geophysics Index (MAGIX) layers using the Geological Survey of Western Australia’s (GSWA) interactive map-viewing application GeoVIEW.WA.
Details of the 2011 East Capricorn Orogen MT traverse and its interpretation are available in Report 135 A magnetotelluric traverse across the eastern part of the Capricorn Orogen.
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