Cover Mapping with Passive Seismics at the Boulia Prospect, Mount Isa Province, Queensland, Australia

Abstract

To determine the thickness of sedimentary cover overlying Proterozoic basement, an ambient-noise surface-wave tomo-graphic (ANSWT) survey was conducted in the Boulia region of the Mt Isa Province in Queensland, Australia. An array of 100 three-component seismic nodes was deployed along a 30 km section and ambient seismic noise was recorded for 19 days. In the resultant seismic model, the top-basement contact is resolved as a sharp, subhorizontal interface at a depth of about 700 m, where seismic velocity (Vs) increases downward from about 2500 to 3500 m/s. The accuracy of the retrieved top-basement contact was confirmed by comparison with drill hole intersections and with results from active seismic and magnetotelluric surveys. This study demonstrates that the ANSWT method can accurately and inexpensively map the thickness of sedimentary cover that obscures potentially mineralised regions globally.