Biogeochemistry of the Ballarat East goldfield

The gold deposits along the crest of the Whitehorse Range were extensively worked last century, and the area was revegetated during the 1930s with Monterey Pine (P. radiata). P. Radiata of different ages were sampled at 25m intervals along two east-west traverses roughly perpendicular to the strike of the Ballarat East field. Sampling occurred during the winter of 1995 following heavy rains. Blackwood (Acacia melanoxylon) and Chinese scrub (Cassinia aculeata) were also sampled for comparative purposes. A third traverse through a belt of remnant eucalyptus (E. obliqua, E. dives, and E. macrorhyncha) was sampled to the south of the pine plantation in 1996. These samples were washed in de-ionised water. Sample material included either leaves or needles, the tips of twigs, and outer bark. The samples were dried, pulverized and analysed using instrumental neutron activation at Lucas Heights, NSW. Gold and As from Cassinia leaves and twigs, and Eucalyptus bark show a good correlation with extensions of known mineralized trends inferred from aerial photographs, as do Ce, Cr, La, Sm, Sc and Th. Samples of P. radiata needles and bark show only a moderate correlation with mineralized trends for Au and As. Repeat sampling to determine sampling variance has revealed probable contamination of Eucalyptus outer bark by dust. Sequential washing experiments indicate that the dust is difficult to remove from fibrous outer bark. Therefore, while application of biogeochemistry to exploration in the central Victorian Goldfields appears feasible, caution must be exercised in the interpretation of data from outer bark for some Eucalyptus species