Element and water cycling in subduction zones from constraints on fluid-mobile element incorporation in serpentine minerals

The main objective of this study is to investigate the incorporation mechanism of the fluid mobile element (FME) strontium in hydrous minerals (serpentine) from HERFD-XANES measurements on natural rock samples. This information is essential to better predict fluid-related geological processes in subduction zones that are not captured directly in natural obducted rocks, including the discharge depth of fluids, their pathways and sources of arc magmas. Data on FME incorporation in minerals of natural rocks are presently not available because the signal of highly diluted trace elements is often obscured by those of major coexisting elements. HERFD-XAS measurements permit to extract the signal of a single element contained in micrometric size mineral phases, but require a high photon flux. This limitations can now be circumvented at the ESRF-EBS that provides the necessary high flux for performing such challenging measurements.