Behavior of chalcophile elements in subduction zones

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I will investigate the behaviour of chalcophile (copper-like) elements in subduction zones where arc volcanoes form. Such elements have an affinity for sulphur in shallow crustal rocks, and include many metals that are necessary for our society, such as copper. Most rocks consist largely of silicates, and the chalcophile elements are present in only trace concentrations. Metal deposits that are economic to mine occur in volcanic arcs that are formed where oceanic rocks are subducted. This spatial association between metal deposits and subduction zones indicates a linkage; however, metal behaviour at great depths, where subduction causes melting of rocks that leads to arc volcanism, is little known. In past research, my team has shown that oxidized magmas contain high concentrations of sulphur and metals, and that the oxidation state reflects the nature of the underlying mantle. The discharge of huge amounts of SO2 from Mt. Pinatubo, Philippines, was a consequence of the highly oxidized mantle below the volcano. We have also shown from work in the Himalayas and S. America that the mantle oxidation condition is affected by the subducted material. The mantle has low sulfur, requiring the large discharge of sulfur from volcanoes to be supplied from the subducted plates. My research will help to answer several questions: How are sulfur and metals transferred from the subducting plate to the mantle, then to magmas that may erupt, and how do these metals occur in the S-poor mantle? For our research, we will study three types of rocks; those that have been deeply subducted and brought back to the surface, pieces of mantle that were uplifted during mountain building, and mantle fragments that were brought to the surface by explosive volcanoes.