GOLD IN VEGETATION AND SOIL - 3 CASE-STUDIES FROM THE GOLDFIELDS OF SOUTHERN WESTERN-AUSTRALIA

Biogeochemistry has not been widely used as an exploration technique f or Au in Western Australia because (1) sampling of soils and other sur ficial materials have been reasonably effective in finding new mineral deposits, and (2) it has been difficult to identify a consistent and regionally typical vegetation sample type. The potential of the techni que has been tested at three sites in the goldfields of southern Weste rn Australia. Vegetation and soil were analysed for Au from the Bounty (Mt Hope), Panglo and Zuleika Au deposits in the southern Yilgarn Cra ton. Gold concentrations in vegetation were generally lower at Panglo and Zuleika compared with Bounty, and probably reflect the depth to mi neralization which is considerably greater at Panglo (40 m) and Zuleik a (20 m) than at Bounty, where it is close to the surface. At Bounty, Au concentrations in dried vegetation varied from < 0.5 ppb in backgro und areas to a maximum of 11 ppb (the highest for any area) over miner alization. In general, the association between Au concentrations in ve getation and mineralization is only weak although, at Zuleika, Mairean a (bluebush) seemed a slightly better sample medium than soil for pred icting the location of underlying mineralization. As the emphasis in e xploration changes to more difficult terrains, the suitability of biog eochemistry needs to be re-examined. These preliminary results from We stern Australia suggest that biogeochemistry may have some role to pla y in the search for deeply buried mineral deposits.