HR: 09:05h
AN: V51B-04    [Abstracts]
TI: Hydrogen Diffusion in Olivine: Implication for Point Defects Models in Olivine
AU: * INGRIN, J
EM: ingrin@lmtg.obs-mip.fr
AF: LMTG Universite Toulouse 3, 14 Av. Edouard Belin, TOULOUSE, 31400, France, Metropolitan
AU: FEROT, A
EM:
AF: LMTG Universite Toulouse 3, 14 Av. Edouard Belin, TOULOUSE, 31400, France, Metropolitan
AB: The knowledge of hydrogen diffusion laws in olivine is essential to explain the zonations observed in some mantle xenoliths [1,2] and to understand the origin of hydrogen-enhanced electrical conductivity and plastic deformation in this mineral [3]. However, despite its importance to understand the mechanisms of hydrogen diffusion no study on the rate of isotopic diffusion of hydrogen is available [4]. Only hydrogen uptake experiments have been performed and were used to infer the diffusivities of hydrogen and of metal vacancies [5,6]. We present here the results of an isotope diffusion study (H-D exchange experiments) undertaken in natural iron-poor olivine single crystals. The results show that diffusion is highly anisotropic with diffusion along [100] almost one hundred times faster than along the two other crystallographic directions. The diffusion laws are more than thirty times slower than the previously measured rates of hydrogen uptake in San Carlos olivine [5]. These results disagree with earlier interpretations. A new point defect model is proposed and metal vacancies diffusivities in olivine are reassessed. [1] Demouchy, S. et al. (2006) Geology, 34, 429-432. [2] Peslier, A.H. and Luhr, J.F. (2006) Earth Planet. Sci. Lett. 242, 302-319. [3] Wang, D. et al. (2006) Nature 443, 977-980. [4] Ingrin, J. and Blanchard, M. (2006) Reviews in Mineralogy &. Geochemistry. 62, 291-320. [5] Kohlstedt, DL. and Mackwell, SJ. (1998) Z. Phys Chem., 207, 147-162. [6] Demouchy, S. and Mackwell SJ. (2006) Phys. Chem. Minerals, DOI 10.1007/s00269- 006-0081-2.
DE: 3902 Creep and deformation
DE: 3904 Defects
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8162 Rheology: mantle (8033)
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly