Baseline geochemical studies in Australia with particular reference to geohealth studies in the Gawler Craton of South Australia

Geoscience Australia and the Cooperative Research Centre for Landscape Environments and Mineral Exploration, in collaboration with State agencies are conducting a series of pilot baseline geochemical surveys （BGS）. These aim to characterize regional geochemical patterns and contribute to what is presently a limited research direction in Australia. BGS can help （1） establish baselines to monitor future change; （2） target mineral exploration; （3） develop informed environmental policies; and （4） geomedical studies on plant and animal well being. In 2004-05, sampling at an average density of 1 sample per 1100 km^2, was conducted in the Gawler Craton, South Australia. In contrast to our pilot region in the Riverina of New South Wales and Victoria, the Gawler lacks well-developed drainage systems and is dominated by aeolian dunes in its western sector. One of the key aims of the Gawler study is to determine whether elemental excesses or deficiencies exist in the regolith and the implications of these for plant, animal and human health. Top （0-10 cm depth） and bottom （～55-90 cm depth） sediment samples were collected in the lower parts of 42 catchments. The compositions of the 〈75 um and 〈180 um fractions were analyzed using XRF （major and some trace elements）, ICP-MS （most trace elements） and ISE （F） methods. Preliminary results show that F, Cr and V are locally elevated above national and international guideline concentrations, raising concerns that these elements may pose potential health issues. Heavy mineral fractions （density 〉2.95） in 4 samples （3 sites） are dominated by iron oxides, spinels, rutile, zircon and barite. Some Cr and V may be related to heavy minerals such as spinels, limiting their bioavailability. Cu, Se and Zn are potentially deficient in parts of the region, but once identified in agricultural areas can easily be remedied through the application of suitable fertilizers.

Baseline geochemical studies in Australia with particular reference to geohealth studies in the Gawler Craton of South Australia