Using seismic tomography to inform mineral exploration in South Australia: the AusArray SA broadband seismic array

Illuminating detailed 3D lithospheric architecture is recognised as a key for enhancing the probability of successful mineral exploration under cover. Passive seismology, and tomography especially, has been at the forefront of illuminating deep earth structure for decades. Current sparse broadband arrays in South Australia are insufficient to delineate the detailed lithospheric architecture needed for robust prospectivity mapping. To improve this, the Geological Survey of South Australia is poised to deploy the AusArray SA broadband seismic array across the eastern-central Gawler Craton, a region encompassing the metallogenic Olympic Cu–Au Province. The seismic array will acquire broadband data at the same station spacing (~0.5º x 0.5º) as the AusLAMP magnetotelluric array. Because seismic and magnetotelluric data have contrasting sensitivities to temperature and composition, the combination of these complementary data at a similar resolution offers the promise of distinguishing between thermal and compositional signals. In particular, signatures of metasomatism and fluid pathways – primary indicators of mineral prospectivity – should be more readily identifiable.
This article provides a brief overview of seismic techniques we will bring to bear on illuminating the seismic structure of the eastern-central Gawler Craton, with a particular emphasis on flavours of tomography. We emphasise that this is a discussion of techniques and their idiosyncrasies rather than a description of the current understanding of the seismic structure of the eastern-central Gawler Craton.