Exploration rock geochemistry for gold, Parkes, New South Wales, Australia

Abstract

The London-Victoria lode-type Au deposit near Parkes, New South Wales, was discovered in 1863 and became the subject of modern exploration in 1980 after about 75 years of little or no activity. The deposit lies within Palaeozoic tuffaceous, andesitic rocks. Soil geochemistry was the main technique used to define drill targets, and the deposit is now at an advanced state of assessment for probable development. Rock geochemistry is being investigated as an aid in drill-core interpretation in the search for extensions to the London-Victoria deposit and other similar deposits in the district. At an early stage of the rock-geochemical work it became clear that minor basemetal mineralization was also present in the structural hanging wall at between 30 and 70 m from the lode Au deposit. Interpretation of the geochemical signatures for major elements (Ca, Mg, Na, K, Fe) and trace elements (Cu, Pb, Zn, Mn) is confused by an overlap and merging of responses from the Au and base-metal mineralization. The measurement of bromine-soluble Sb, As, Bi, and Te, together with the more conventional major and trace elements, permits discrimination between geochemical halos related to the Au and those resulting from minor base metal mineralization. The results demonstrate the use of rock geochemistry for Au exploration, its usefulness in drawing attention to geological features, and the utility of bromine-soluble trace elements commonly associated with gold mineralization.