Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Abstract Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mungall, J. E. Articles by Naldrett, A. J. Search for Related Content GeoRef GeoRef Citation

Ore Deposits of the Platinum-Group Elements

Department of Geology, University of Toronto, 22 Russell Street
Toronto, Ontario, M5S 3B1, Canada
E-mail: mungall{at}geology.utoronto.ca

Anthony J. Naldrett

Department of Geology, University of Toronto, 22 Russell Street
Toronto, Ontario, M5S 3B1, Canada

View larger version (18K): [in this window] [in a new window]   FIGURE 1 Compositions of major Earth reservoirs and the principal ore deposits of PGE (recalculated to 100% sulfide) shown as the concentrations of chalcophile metals normalized to those in CI chondrites. Core formation has stripped most of the PGE from the mantle (pyrolite). The formation of continental crust from the mantle has led to even greater impoverishment; it is primarily by high-degree partial melting of mantle rock that PGE-rich magnesian magmas like komatiite can form. The Merensky Reef approaches the maximum possible PGE enrichment in sulfide melts; the sulfide in the UG-2 has probably been enriched by secondary processes. DATA FROM NALDRETT (2004) AND SOURCES THEREIN

View larger version (82K): [in this window] [in a new window]   FIGURE 2 Processes governing the formation of PGE deposits. Sulfides (red dots) persist in the mantle during early stages of mantle melting and are not exhausted until much melting has occurred. PGE deposits may form in layered intrusions when magmas reach sulfide saturation during fractional crystallization, by transport of PGE-rich fluids through cumulate crystal piles ("uppers"), or by magma recharge and mixing events ("downers"). The Noril'sk deposit type occurs when fertile magma in a magma conduit encounters sulfide-rich sediments and becomes sulfide saturated.

View larger version (46K): [in this window] [in a new window]   FIGURE 3 Contributions of different ore deposits to global production and reserves of Pt, Pd, and Rh

View larger version (115K): [in this window] [in a new window]   FIGURE 4 Field exposure of the UG-1 chromitite in the vertical wall of the Dwars River gorge, Upper Critical Zone of the Bushveld Complex, South Africa. Chromitites in the Bushveld Complex supply a significant amount of the world's platinum, palladium, and rhodium (UG-2; FIG. 3). The UG-1 chromitite, which is interlayered with plagioclase-rich rocks (predominantly anorthosite), is laterally extensive across the Bushveld Complex and is noted for its unusual bifurcating layers. PHOTO COURTESY OF CRAIG FINNIGAN