subduction zones; aqueous fluid-silicate melt interactions; element partitioning; diamond anvil cell; Synchrotron X-ray fluorescence spectroscopy; Cu complexation; X-ray absorption spectroscopy; speciation; Synchrotron X-ray fluorescence spectroscopy (SXRF); ore deposition
Carmen Sanchez-Valle (2013), Structure and Thermodynamics of Subduction Zone Fluids from Spectroscopic studies, in Andri Stefansson Thomas Driesner and Pascale Benezeth (ed.), Mineralogical Societry of America MSA, 1/1/2013, 265-309.
Marion Louvel, Carmen Sanchez-Valle, Wim J. Malfait, Denis Testemale, Jean-Louis Hazemann (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.
This proposal is split into two subprojects, Project A to support a PhD student Marion Louvel (and successor) and Project B to support a Post-doctoral researcher Wim J. Malfait (or his successor).Fluids and melts circulating through the Eath’s interior play a fundamental role in many geological processes, including the recycling of lithophile elements back into the mantle in subduction zones or the formation of economically important metal deposits. A quantitative understanding of these processes requires knowledge of fluid-melt partition coefficient of trace elements and the stability of metal complex at high pressure and temperature conditions.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 (800 ?C and 2 GPa). Project B will investigate the stability and structure of Cu complexes in hydrothermal-magmatic fluids at elevated pressure and temperature conditions (800 ?C and 2 GPa).Project A- Mobilization of trace elements in subduction zones: effect of melt and fluid compositionKnowledge 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 Zr, Sr, Pb and REE elements between silicate melts (haplogranite and phonolite compositions) and aqueous fluids (water, chlorine-, fluorine- and boron-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. Project B- Copper complexation in hydrothermal-magmatic fluidsThe transport and deposition of copper in saline hydrothermal fluids are controlled by the stability of copper(I) complexes with ligands such as chloride. Although the speciation of Cu is well constrained at the conditions of ore deposition, much less is know about its behavior during the early stages of the ore-forming process in which it is extracted from the magma during degassing and transported hydrothermally to the place of deposition. This project will investigate the stability and structure of Cu-complexes in magmatic fluids (NaCl brines and alkali-Al-SiO2-bearing aqueous fluids) up to 750 C and 2 GPa using X-ray absorption spectroscopy in hydrothermal diamond anvil cells. The interpretation of the experimental data will be assisted by ab initio molecular dynamic simulations. This results will improve our understanding of the transport and deposition of elements during magmatic-hydrothermal conditions and the recycling of ore-forming metals in subduction environments.