A first-pass inspection of regional airborne electromagnetic data in Western Australia

The AusAEM20-WA program to acquire regional airborne electromagnetic (AEM) data at a nominal 20 km line-spacing across Western Australia is a National Collaborative Framework Agreement project between the Geological Survey of Western Australia (GSWA) and Geoscience Australia (GA), funded through the Western Australian Government's Exploration Incentive Scheme, the State government's COVID-19 recovery plan, and the Commonwealth Government's Exploring for the Future (EFTF) programs. AusAEM20-WA follows GA's and GSWA's rationale of aiming for State-wide coverage of geophysical data that provide context and confidence to encourage more detailed, higher resolution acquisition programs directed at local resource exploration. After completion of acquisition and processing by February 2023, more than 160 000 line km of data (Fig. 1) can be downloaded from GSWA's MAGIX and GA's eCat databases The data and derived products can be used to map the thickness and conductivity character of sedimentary and regolith cover to depths to 600 m, as well as the topmost portion of the underlying basement. Data, and derived products provide information on near-surface structure and can help assess mineral, energy and groundwater resource studies. Overall, the regolith-rock interface is well imaged across the State. On some sections, numerous conductive horizons within the regolith profile can be identified along with discrete paleochannels. The Phanerozoic rocks in the Canning, Perth, and Carnarvon Basins, are generally more conductive than the surrounding Precambrian rocks. The greater conductivity may be related to the higher proportion of conductive shale units, as well as higher moisture levels in the more porous and permeable sedimentary units. Preliminary camp-scale investigations across the State show that the data are useful to mineral explorers, as some conductive anomalies in the basement can be correlated to known deposits. Particularly conductive rock types such as lamproite pipes (or, at least their altered tops) can be distinguished from the surrounding sedimentary rocks. ASX announcements that followed within a few weeks of the data release have shown that explorers are using the data and prioritizing anomalies for further investigation.