HR: 0800h
AN: V31C-0601    [Abstracts]
TI: Fluid-mineral interactions in subduction zones: insights from experiments in the diamond- anvil cell
AU: Sanchez-Valle, C
EM: carmen.sanchez@erdw.ethz.ch
AF: Institute for Mineralogy and Petrology, Department of Earth Sciences, ETH Zurich, Clausiusstrasse 25 NW, Zurich, 8092, Switzerland
AU: * Daniel, I
EM: isabelle.daniel@univ-lyon1.fr
AF: Laboratoire des Sciences de la Terre, CNRS UMR5570, Ecole Normale Superieure de Lyon, Universite Claude Bernard Lyon 1, 46, Allee d'Italie, Lyon, 69007, France
AU: Bass, J D
EM: jaybass@uiuc.edu
AF: Department of Geology, University of Illinois at Urbana-Champaign, 1301, W. Green Street NHB 245, Urbana, IL 61801, United States
AU: Reynard, B
EM: breynard@ens-lyon.fr
AF: Laboratoire des Sciences de la Terre, CNRS UMR5570, Ecole Normale Superieure de Lyon, Universite Claude Bernard Lyon 1, 46, Allee d'Italie, Lyon, 69007, France
AB: Volatile-rich high-pressure fluids released into the mantle during the subduction of the oceanic lithosphere have a broad impact on the mass transfer in the Earth since they mediate the recycling of elements into the mantle and their return to the atmosphere through arc volcanism. Constrains on element transport and mass fluxes in these environments rely on quantitative thermodynamical modeling of fluid-mineral interactions, that is greatly limited by the lack of thermodynamic data of aqueous fluids at high pressure and temperature conditions (10 GPa – 800 C). As a part of the efforts to adress this problem, this contribution will present recent results on it in situ studies of fluid-mineral interactions at high P-T conditions in the diamond anvil cells using synchrotron X-ray and vibrational spectroscopies. Experiments designed to measure in situ the solubility of mineral, the distribution of stable isotopes between minerals-melts-fluids and the density of aqueous fluids will be presented. Synchrotron X-ray Fluorescence spectroscopy (SXRF) has been used to conduct it in situ dissolution/precipitation kinetics studies and mineral solubility measurements with detection limits as low as 40 ppm in the diamond-anvil cell. Results on the solubility of carbonate minerals in water will be shown to illustrate the potentials of the technique for in situ observations of mineral-fluids interactions at extreme conditions. In another example we report investigations on the systematic of boron isotopic fractionation between mineral/melt/fluid at subduction zone conditions. Boron isotopic fractionation factors between trigonal B(OH)₃ and tetragonal B(OH)₄^- aqueous species at high P-T conditions (10 GPa – 500 C) were calculated using measured vibrational spectra (Raman and IR) and thermodynamical modeling following Urey's theory. Combining these results with previous data on B-isotopic fractionation between minerals/melts/fluids we propose a model in which B-isotopic exchanges at high P-T conditions can be quantitatively predicted from coordination changes between phases, be it solids or fluids. Finally, efforts on the evaluation of the thermodynamic properties of high pressure fluids will be illustrated by the determination of the equations of state from sound velocity measurements in the diamond-anvil cell by Brillouin scattering spectroscopy. Densities of H2O and NaCl-H2O fluids will be presented and discussed in comparison with literature data.
DE: 1011 Thermodynamics (0766, 3611, 8411)
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 3924 High-pressure behavior
DE: 3934 Optical, infrared, and Raman spectroscopy
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting