The Frome airborne electromagnetic (AEM) survey (Figure 1) was designed to deliver reliable, pre-competitive AEM data and scientific analysis for the energy resource potential of the Frome region of South Australia. The Frome AEM survey is the last and largest of three regional AEM surveys flown under the 5-year Onshore Energy Security Program (OESP) by Geoscience Australia (GA) in the interests of reducing risk and stimulating exploration investment for uranium.

The Frome AEM survey was flown between 22 May and 2 November 2010, is approximately 95 450 km2 in area and collected 32 317 line km of new data at an average flying height of 100 m. The Frome survey complements earlier surveys in the Paterson Province (Western Australia; Roach, 2010) and the Pine Creek area (Northern Territory; Craig, in prep.). The Frome survey was flown in conjunction with the PIRSA Cariewerloo Basin survey (Hutchinson and Costelloe, 2010; PIRSA, 2010; Wilson et al., 2011) using the same aircraft and survey parameters.

The Frome AEM survey includes the Marree (pt), Callabonna (pt), Copley (pt), Frome (pt), Parachilna (pt), Curnamona, Olary and Chowilla (pt) 1:250 000 sheets and was flown largely at 2.5 km line spacing, with the northern portion flown at 5 km line spacing (Figure 1). Survey partners included GA, PIRSA and an industry consortium. The survey aims to assist regional-scale mapping of subsurface geological features associated with uranium systems as well as general geological and groundwater mapping. The geological features targeted by the AEM mapping program include:

- Palaeochannel-hosted sandstone uranium systems in the Frome Embayment;

- Faults which may have acted as fluid pathways (e.g., the Poontana and Wooltana faults);

- The Benagerie Ridge (a buried Paleoproterozoic basement high in the Curnamona Province);

- Thickness of cover sediments over Proterozoic and Paleozoic rocks;

- Units within the Namba Formation, particularly the Beverley Sands, which are prospective for uranium deposits, overlying the Alpha Mudstone;

- Cenozoic strandlines for heavy mineral deposits in the Murray Basin;

- Erosion surfaces on Mesozoic which may constrain Cenozoic valley development;

- Proterozoic basement sulfide deposits (e.g., White Dam Au, Portia Cu-Au-Mo, Mutooroo Cu-Co-Au, Kalkaroo Cu-Au);

- Proterozoic basement iron ore deposits (e.g., Mutooroo, Razorback Ridge);

- The Delamerian Orogen under the Murray Basin; and,

- Groundwater.

The survey results indicate a depth of investigation (depth of reliable signal penetration) of up to 400 m in areas of thin cover and resistive basement (e.g., Adelaidean rocks in the Olary Ranges) and up to about 100-150 m in Cenozoic Mesozoic sediments in the Frome Embayment and Murray Basin. A range of under-cover features are revealed, including (but not limited to): extensions to known palaeovalley networks in the Frome Embayment; the under-cover extent of the Benagerie Ridge; regional faults in the Frome Embayment and Murray Basin; folded and faulted Neoproterozoic rocks in the Adelaide Fold Belt; Cenozoic Mesozoic stratigraphy in the Frome Embayment; neotectonic offsets in the Lake Eyre Basin; conductive Neoproterozoic rocks associated with copper-gold mineralisation; and, coal-bearing structures in the Leigh Creek area.

Phase 1 (contractor-delivered) data (Hutchinson, 2011) are now available for free download from: http://www.ga.gov.au/energy/projects/airborne-electromagnetics.html or on DVD-ROM ($99) from the GA Sales Centre.