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Abstract:
Lithospheric cratons withstand significant tectonic events over time due to their strong rheology and buoyancy. The Archean-Proterozoic Gawler Craton, South Australia, experienced heightened tectonic activity between 2.0 and 1.4 billion years ago, leading to a metasomatised mantle signature and world-class mineral systems including iron-oxide copper gold (IOCG) deposits and gold deposits. While the various deposit styles are often hundreds kilometers apart, vast arrays of magnetotelluric (MT) data point to a common primary architecture, in which the deposits are ultimately linked to a common metasomatised mantle source. Along the eastern margin of the Gawler Craton, the IOCG deposits have been extensively imaged with MT, including the super-giant Olympic Dam deposit. Here, we present new magnetotelluric data across a 12.5 km array and two closely spaced profiles totalling ~ 400 new broadband MT stations, across the western margin of the Gawler craton. The new data reduces the 50 km site spacing from the existing AusLAMP (Australian Lithospheric Architecture Magnetotelluric Project) by a factor of four to increase the resolution of the resistivity structure from the lower to upper crust. The scale reduction will constrain the magma and fluid pathways in between Archean lithologies present in the crust beneath the survey area and inform the genesis of the prevailing gold and nickel-copper deposits throughout the western Gawler craton. The 3D models show unprecedented insight into fossilised pathways of Proterozoic fluid flux along the craton margin.
