North Australia Wide Activities
Over the last half a century mineral resource discovery in Australia has been underpinned by national surface geology mapping supplemented by magnetic and gravity geophysical datasets. In order to meet the challenge of exploring undercover, a new era of subsurface geological mapping is required, supplemented by additional new geophysical techniques capable of imaging aspects of the subsurface geology. Both the geological and geophysical mapping programs are working towards coverage of northern Australia. Some of these data acquisition and data interpretation programs are world firsts while others tie into past collaborative efforts historically focused in southern parts of Australia.
A new generation of seamless continental-scale geological mapping commenced as part of the Exploring for the Future program. This new approach involves interpretations of the subsurface geology beneath geological sequences of the Cenozoic, Mesozoic, Phanerozoic and Neo-proterozoic Eras, which overlie older prospective rocks. In parallel the thickness of each of the four aforementioned cover sequences is being constrained so that the economic search space can be defined for mineral resource development. These two mapping programs formed the foundations for a 3D geological model of northern Australia, which will also be useful for energy and groundwater resource assessment purposes. In order to unravel the geological evolution of the older covered rocks and assess their mineral potential an isotopic fingerprinting program was also carried out.
Both the geological and cover-thickness mapping programs depend on the extensive geophysical acquisition program. The airborne electromagnetic survey (AusAEM) is the world's largest survey of its kind and will map the electrical conductivity structure to a depth of a few hundred metres below the earth's surface. The AEM data has permitted the thickness and the character of the cover to be mapped while also identifying direct mineral exploration targets within the basement. The Australian Lithospheric Architecture Magnetotellluric Program (AusLAMP) and Passive Seismic Array (AusArray) are both national collaborative efforts between Geoscience Australia, universities and state surveys which to date have been predominantly focused in southern parts of Australia. Both programs have provided the world's highest resolution continental mapping of the deep electrical conductivity (using magnetotelluric methods) and seismic velocity structure of the north Australian plate, respectively. Such data have been shown elsewhere to image the root zones of major mineral systems, thereby mapping broad areas of 'fertile' lithosphere which are targets for more detailed follow-up mineral exploration.