Particle size and trace element distribution characteristics of cassiterite as an aid to provenance study of stanniferous placers in northeastern Tasmania, Australia

Abstract

In order to assist a heavy mineral provenance study of stanniferous placers in northeastern Tasmania, Australia, particle size and trace element distribution characteristics of cassiterite were examined. The contents of four trace elements: niobium (Nb), tantalum (Ta), tungsten (W), and zirconium (Zr) within cassiterite were determined using wavelength X-ray fluorescence spectrometry. This was carried out to test the diagnostic value of these elements in recognizing different types of primary tin mineralization in order to provide clues on the distance of transport of cassiterite. Cassiterites from the Blue Tier and Mount Cameron Massifs have been found to show differences with the former enriched in W and the latter enriched in Nb, Ta and Zr. These differences are explained by a greisen- and a pegmatite-predominated source rock, respectively. The particle size distribution characteristics of cassiterite concentrates obtained from mines were found to be a valuable means of distinguishing between placers showing kulit, kaksa and mintjan affinities. Based on the dominance of kulit and kaksa placers found, and records of ore distribution in deep leads, it is concluded that the bulk of the economic placers in northeastern Tasmania are locally derived and do not normally exceed 1 km in distance of transport downstream of the source rock.