Partition and speciation of Arsenic (As) in magmatic-hydrothermal fluids: implications for the formation of Au-As ore deposits

Arsenic (As) is an indicator for the formation of some of the largest hydrothermal gold (Au) deposits. However, the conditions of extraction of As from magmas and its transport by magmatic volatiles remain poorly understood. Here we will determine the partition coefficients of As between granitic melts and Cl/S-bearing aqueous fluids and its speciation to provide new insight into the formation of Au-As deposits. Fluid-melt partitioning and speciation experiments will be performed in the FAME autoclave in conjunction with synchrotron X-ray Fluorescence (SXRF) and absorption (XAS) spectroscopy at BM16B (FAME-UHD) beamline.