aqueous fluid-silicate melt interaction; elemental partitioning; speciation; diamond anvil cell; Synchrotron X-ray fluorescence spectroscopy; X-ray absorption spectroscopy; subduction zones; aqueous fluid-silicate melt interactions; SXRF; XANES and EXAFS
Louvel Marion, Sanchez-Valle Carmen, Malfait Wim J, Testemale Denis, Hazemann Jean-Louis (2013), Zr complexation in high pressure fluids and silicate melts and implications for the mobilization of HFSE in subduction zones, in Geochimica et Cosmochimica Acta
, 104, 281-299.
Malfait Wim J, Verel Rene, Ardia Paola, Sanchez-Valle Carmen (2012), Aluminum coordination in rhyolite and andesite glasses and melts: Effect of temperature, pressure, composition and water content, in Geochimica et Cosmochimica Acta
, 77, 11-26.
Malfait Wim J, Xue Xianyun (2010), The nature of hydroxyl groups in aluminosilicate glasses: Quantifying Si-OH and Al-OH abundances along the SiO2-NaAlSiO4 join by H-1, Al-27-H-1 and Si-29-H-1 NMR spectroscopy, in Geochimica et Cosmochimica Acta
, 74, 719-737.
Malfait Wim J, Xue Xianyn (2010), The partial H-1 NMR spectra of Al-OH and molecular H2O in hydrous aluminosilicate glasses: Component-Resolved analysis of Al-27-H-1 cross polarization and H-1 spin-echo MAS NMR spectra, in SOLID STATE NUCLEAR MAGNETIC RESONANCE
, 37, 60-68.
Malfait Wim J (2009), Quantitative Raman spectroscopy: speciation of cesium silicate glasses, in Journal of Raman Spectroscopy
, 40, 1895-1901.
This proposal is split into two subprojects, Project A to support a PhD student and Project B to support a Post-doctoral researcher.Fluids and melts liberated from subducted oceanic crust recycle lithophile elements back into the mantle wedge, facilitate melting and ultimately lead to prolific subduction -zone arc volcanism. The nature and the composition of the mobile phases generated in the subducting slab at high pressures have, however, remained largely unknown. The use of trace elements as indicators of the origin and petrogenesis of magmatic systems is based upon a detailed knowledge of how they partition between coexisting solid, melt and fluid phases of hydrous magmatic systems. Studies of their structural properties and distribution in individual phases of a hydrous silicate melt coexisting with a hydrothermal fluid are needed to provide a better understanding of the nature of partitioning of trace elements in magmatic-hydrothermal systems. This proposal aims to investigate in situ the interactions between aqueous fluids and silicate melts at high pressure and temperature conditions using Synchrotron-based X-ray spectroscopic techniques combined with externally heated diamond anvil cells. Project A is aimed at the partitioning of selected trace elements between aqueous fluids and silicate melts at conditions relevant for the genesis of magmas (1000 ?C and 2-3 GPa). Project B will investigate the speciation and local structural environment of selected trace elements in aqueous fluids, silicate melts and supercritical liquids of intermediate composition.A- Trace element partitioning between aqueous fluids and silicate melts at high P-T conditions: implications for the genesis of magmas in subduction zonesKnowledge of the partitioning of trace elements between silicate melts and coexisting aqueous fluids is essential for the understanding of mass transfer during magma genesis and late stage magmatic processes. The project investigates the effects of composition, pressure and temperature in the partition coefficients of a set of trace elements between silicate melts (haplogranite and nepheline compositions) and aqueous fluids (water, chlorine- and carbonate-rich fluids). Partitioning experiments will be conducted in situ using Synchrotron X-ray fluorescence spectroscopy (SXRF) in conjunction with the diamond anvil cell. The results will allow constraining the particular geochemical signature of the two principal vehicles for mass and energy transport in the Earth’s interior. B- Speciation of selected trace elements in aqueous fluids, silicate melts and supercritical liquids at high pressure and temperature conditions Information concerning the trace element speciation in mobile phases expelled from subducted slabs is required for understanding the transport properties as well as the geochemical process controlling the formation of magmas. This project attends to investigate in situ the speciation of two key trace elements, Sr and Nb, in silica-rich aqueous fluids, hydrous silicate melts and supercritical liquids. Speciation measurements will be conducted at high P-T in the diamond anvil cell using X-ray absorption fine structure XAFS spectroscopy. Integrated results for partitioning and speciation data obtained in these studies will be of fundamental importance in the development of a clear understanding of chemical mass transfer and magma generation in convergent margins.