Economic platinum concentrations in sediment-hosted orogenic gold deposits?

摘要

Several authors have documented economic levels of Pt and sometimes Pd and Os in numerous sediment-hosted orogenic gold deposits of the former Soviet Union. We review the geology of three of these deposits (Sukhoi Log, Natalka, Kumtor) and present new analytical data on suites of samples from these deposits as well as from sediment-hosted orogenic gold deposits in the central Victorian gold province of SE Australia. Although significantly elevated concentrations of platinum-group elements (PGE) are present in some deposits (Pd ≤ 30ppb; Pt ≤15 ppb), these new data do not support the presence of economic levels of PGE in the deposits investigated. Nonetheless, theory predicts that if the hydrothermal solutions were reduced and sulphur-rich then bisulphide complexing of Pt and Pd could have generated economic concentrations of these metals. Lack of PGE minerals in placers derived from the hard-rock deposits may be because Pt has been dissolved in oxidised surface waters and transported considerable distances from its source.