Application of Multi-Scale Magnetotelluric Data to Mineral Exploration: An Example from the East Tennant Region, Northern Australia

The footprint of a mineral system is potentially detectable at a variety of scales, from ore deposits to the Earth’s crust and lithosphere. Magnetotellurics is one of few techniques that can provide multi-scale datasets to understand mineral systems. We have used long-period data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) as a first-order reconnaissance survey to resolve large-scale lithospheric architecture for mapping areas of mineral potential in northern Australia. The 3D resistivity model reveals a broad conductivity anomaly extending from the Tennant Region to the Murphy Province in the lower crust and upper mantle, representing a potential fertile source region for mineral systems. Results from higher-resolution infill magnetotelluric survey reveal two prominent conductors in the resistive host whose combined responses result in the lithospheric-scale conductivity anomaly mapped in the AusLAMP model. Most importantly, conductive structures indicate a “favorable” crustal architecture linking the lower, fertile source regions with depositional sites in the upper crust. This observation strongly suggests that the major faults are deep-penetrating structures that potentially acted as pathways for transporting metalliferous fluids to the upper crust where they could form mineral deposits. This result and its integration with other datasets suggest high prospectivity for major mineral deposits in the vicinity of these major faults. In addition to this contribution, interpretation of high-frequency magnetotelluric data helps characterise cover and assist with stratigraphic drill targeting which, in turn, will validate the models and improve our understanding of basement geology, cover sequences and mineral potential. This study demonstrates that integration of geophysical data from multi-scale surveys is an effective approach to scale reduction during mineral exploration in covered terranes with limited geological knowledge. Citation: Wenping Jiang, Jingming Duan, Michael Doublier, Andrew Clark, Anthony Schofield, Ross C Brodie, James Goodwin, Application of multiscale magnetotelluric data to mineral exploration: an example from the east Tennant region, Northern Australia, Geophysical Journal International, Volume 229, Issue 3, June 2022, Pages 1628–1645, https://doi.org/10.1093/gji/ggac029