HR: 09:00h
AN: V11C-05    [Abstracts]
TI: In situ determination of Pb, Sr, Rb, Zr partitioning between hydrous melts and aqueous fluids at high pressure and temperature
AU: * BUREAU, H
EM: hbureau@drecam.cea.fr
AF: Lab. Pierre Sue, UMR9956, CEA Saclay, Gif sur Yvette, 91191 France, Metropolitan
AU: MENEZ, B
EM: menez@ipgp.jussieu.fr
AF: LGM, IPG Paris 4 place Jussieu, Paris, 75252 France, Metropolitan
AU: MALAVERGNE, V
EM: Malavergne@lpi.usra.edu
AF: L. Geomat‚riaux, IFG, Marne la Vall‚e, 77454 France, Metropolitan
AU: SOMOGYI, A
EM: somogyia@esrf.fr
AF: ESRF, BP220, Grenoble, 38043 France, Metropolitan
AU: MUNOZ, M
EM: munoz@esrf.fr
AF: ESRF, BP220, Grenoble, 38043 France, Metropolitan
AU: SIMIONOVICI, A
EM: simion@esrf.fr
AF: ESRF, BP220, Grenoble, 38043 France, Metropolitan
AU: MASSARE, D
EM: massare@drecam.cea.fr
AF: Lab. Pierre Sue, UMR9956, CEA Saclay, Gif sur Yvette, 91191 France, Metropolitan
AU: BURCHARD, M
EM: Michael.burchard@ruhr-uni-bochum.de
AF: Inst. fur Geologie, Mineralogie, geophysik, Ruhr Universit„t Bochum, Bochum, 44801 Germany
AU: KUBSKY, S
EM: kubsky@accel.de
AF: Lehrstuhl fur Experimentalphysik III, Ruhr Universit„t Bochum, Bochum, 44801 Germany
AU: SHAW, C
EM: cshaw@unb.ca
AF: Dept of Geologie, Univ of New Brunswick 2 Bailey Drive New Brunswick, Fredericton, E3B 5A3 Canada
AB: The combination of experiments performed in diamond anvil cells and in situ synchrotron light source measurements represents a powerful tool for studying the petrogenesis of subduction-related magmas. We have undertaken a program of partitioning experiment coefficient determination between silica-rich hydrous melts and aqueous fluids of various compositions (ñ NaCl) for Pb, Sr, Rb and Zr at high pressures (up to 1.5 GPa) and temperatures (up to 900øC), using the X-ray microprobe of the ID22 ESRF beamline. Experiments were carried out in a Bassett-modified diamond anvil cell. We measured the equilibrium between aqueous fluids and silicate melts before, and/or after, their complete miscibility was reached, allowing the calculation of partition coefficients for the studied element (i): Difluid/melt=Cifluid/Cimelt. Our experimental results show that for the studied elements the partitioning process strongly depends on the composition of the aqueous phase in equilibrium with the melt. Indeed, the presence of Cl in the starting aqueous solution favours a significant affinity of Pb, Rb, Sr for the melt phase, whereas without Cl, there is no strong partitioning of these elements into either the aqueous or the hydrous silicate phase. Difluid/melt values will be presented together with elemental distribution maps obtained inside the cell. This strong affinity for silicate melt in the presence of an NaCl aqueous solution implies that saline aqueous fluids may play a key role in the generation of arc magmas. These fluids may also act as initiators of the geochemical fingerprint of arc-related magmas. Trace element transport by silica-rich hydrous fluids may also be considered as an efficient metasomatic agent in the mantle during elemental recycling in subduction zones.
DE: 8434 Magma migration
DE: 8494 Instruments and techniques
DE: 3630 Experimental mineralogy and petrology
DE: 1030 Geochemical cycles (0330)
DE: 1065 Trace elements (3670)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting