Trace element features of slab-fluids under high-pressure and high-temperature conditions using synchrotron x-ray fluorescence analysis

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Using a micro-focused synchrotron x-ray beam, in-situ x-ray fluorescence spectra are obtained from aqueous fluids and haplogranite or jadeite melts under varied concentrations of (Na, K)Cl. Partition coefficients between the aqueous fluids and melts are calculated for Pb, Rb, and Sr. There is a positive correlation between the partition coefficients and pressure, as well as the partition coefficients and salinity. As compared to the saline fluids with 25 wt.% (Na, K)Cl, the Cl-free aqueous fluids can only dissolve one tenth (Pb, Rb) to one fifth (Sr) of the amount of large ion lithophile elements when they coexist with the melts. In the systems with 13-25 wt.% (Na, K)Cl, the partition coefficients of Rb and Pb are greater than unity, indicating the capacity of such highly saline fluids to effectively transfer Pb and Rb.