SA/NT tech talk: Crustal resistivity of the Mt Gambier subprovince: origins of the Newer Volcanics and implications for exploration in the Western Otway

Title: Crustal resistivity of the Mt Gambier subprovince: origins of the Newer Volcanics and implications for exploration in the Western Otway

Presenter: Sam Jennings

Location: Thomas Cooper Room, Coopers Alehouse, 316 Pulteney St, Adelaide

Date: Tuesday 5th October 2021

Time: 5:30 pm for a 6:15 pm start

Cost: Members and students free, non-members $10, includes finger food and drinks

Abstract:

The westernmost Mt Gambier subprovince of southeast Australia's Newer Volcanics Province represent the most recent eruptions of a continental, intraplate volcanic province. Recent magnetotelluric (MT) models in the wider region reveal an extensive conductor beneath Central Victoria as well as a separate, crustally-bound region of low resistivity beneath the Mt Gambier subprovince. To better resolve this western conductor, 49 new broadband MT sites are collected at 25 km spacing and crustal resistivity is modelled using the latest 3D inversion algorithms. An extensive region of low resistivity (<100 Ω m) is revealed and interpreted as the footprint of rising magmatic fluids that cause widespread alteration of Delamerian crust. Spatial alignment of this feature with step-like sub-lithospheric topography lend credence to theories of edge-driven convection and shear-driven upwelling as causal mechanisms for melt generation. A localised zone of even lower resistivity (< 10 Ω m) in the mid-crust beneath the town of Casterton, Victoria is interpreted as small amounts of partial melt. In this presentation, I'll discuss the origins of the NVP, the role of complex basement structures in providing fluid pathways and the implications of a distal melt source for exploration in the Western Otway Basin.