A systematic experimental study will be conducted to obtain quantitative information on the distribution of Cu, Au and S between andesitic and basaltic silicate melts and volatile phases. The experiments will be carried out in cold seal and internally heated pressure vessels, at various conditions characteristic of upper crustal magma reservoirs. The fluid phase will be trapped as synthetic fluid inclusions in mafic minerals or in fine grained mineral traps at the experimental run conditions. The chemical composition of the phases and the speciation of the elements will be analyzed using LA-ICPMS and X-ray Absorption Spectroscopy, respectively. From these data, the partition coefficients of S, Cu and Au between the fluid and the melt will be calculated and interpreted in a thermodynamic framework. The results will be used to build mass transfer models to assess the efficiency of the spatial redistribution of S, Cu and Au through volatiles within complex magmatic reservoirs at various physical and chemical conditions. These models will lead to a better understanding of processes responsible for formation of porphyry-type ore deposits and the controls on the composition of emitted gases by active volcanoes.
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