Selenium and sulfur in the Bushveld complex: Implications for the formation of the platinum-group element deposits

摘要

@@Selenium/sulfur ratios have long been used as indication of the processes that have affected base metal sulfides. Loftus-Hills and Solomon (1967) found that pyrites formed from hydrothermal fluids have higher Se/S ratio than those formed from low temperature fluids. Eckstrand et al. (1989) used the Se/S ratios to document contamination of mafic magmas by sediments. Peck and Keays (1990) used Se/S ratios to consider whether S had been remobilized from magmatic deposits. Lorand et al. (2003) used Se/S ratios in mantle nodules to suggest that S has been lost from most nodules. Despite the utility of the ratio there are few studies on the behavior of Se in crustal rocks. In part, this is due to the very low level at which this element occurs in the crust [the average continental crust contains only 0.050 ppm (Taylor and McLennan ,1985). In order to determine Se at low levels, we have recently modified an analytical method, consisting of Se pre-concentration on thiol cotton fiber, and adapted it for instrumental neutron activation analysis (Se/TCF-INAA, Savard et al. 2006). The ability to determine Se at low levels offers the opportunity to study a wider range of rocks and processes.