Mineralogy of the oxidised zone at the New Cobar orebody

The “signature” for geochemical dispersion in the supergene environment for “Cobar-style” mineralisation is not well understood. Such an understanding would be germane to the development of exploration models that could be applied to deeply weathered terrane in the Cobar region. It would in turn rest on an understanding of the oxidized zone mineralogy that forms above the water table and although this is known in the most general terms, no recent systematic study of oxidized mineralogy in the region has been undertaken. The current open cut mining operation associated with the New Cobar orebody has provided an unparalleled opportunity to study the oxidized zone of Cobar-style deposits. The deposit is located in the central west of New South Wales, approximately 3 km south of the township of Cobar and is one of a number of north-south trending, structurally controlled, gold and base metal deposits in the area, including the New Occidental and Peak mines to the south, and the CSA and Elura mines to the north. An extensive study of the mineralogy of the oxidized zone at New Cobar has now been carried out. New Cobar is primarily a gold-copper deposit carrying minor lead, zinc, bismuth and other base metals in minor to trace amounts. Mineralisation is contained wholly within the Devonian age Great Cobar Slate formation and forms an elongated lens associated with a steeply dipping, second order splay from the Great Chesney fault (Stegman & Pocock 1996). The study has identified a large suite of copper and lead minerals, a significant proportion of which have not been previously reported from the Cobar mining area