| Summary: | There are few reliable analyses of Au in mantle sulfides. In this study, Au has been measured by LA-ICP-MS along with major and trace elements in sulfides in peridotite xenoliths from the Svalbard Archipelago. Three groups of xenoliths have been recognised in these samples: (a) Group I are modally metasomatised peridotites, modified by carbonate-rich melts; (b) Group II are cryptically metasomatised peridotites (LREE enrichment with no new phases added); (c) Group III are depleted, with no obvious metasomatic over print. The metasomatism of group I and II xenoliths may be related by chromatographic fractionation. Each group has a distinct sulfide assemblage. Group I sulfides are homogeneous, with low concentrations of chalcophile elements, including Au. The group II sulfides show a distinct enrichment in trace elements, especially As, Ag, Pb, Bi, incompatible PGEs (Pd, Pt, Rh), and Au. These sulfides were introduced by the carbonate-rich agent that metasomatised the samples. Two distinct sulfides are observed in Group III xenoliths: type 3(a) has very low trace-element concentrations, and strong depletion in Au relative to both the PGEs, and the other sulfides. These are depleted sulfides. Type 3(b) is depleted in Au relative to the PGEs but has higher Au (and PGE) content than any other sulfide observed in this study. The characteristics of these sulfides are intermediate between the depleted 3(a) sulfides and the metasomatic (Group II) sulfides, and possibly formed by mixing.
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