HR: 0800h
AN: U11A-0022    [Abstracts]
TI: Si isotopic composition of the Earth's mantle and meteorites
AU: * Fitoussi, C
EM: fitoussi@erdw.ethz.ch
AF: ETH Zurich, Institue of Isotope Geochemistry and Mineral Resources, Clausiusstrasse 25, Zurich, 8092, Switzerland
AU: Bourdon, B
EM: bourdon@erdw.ethz.ch
AF: ETH Zurich, Institue of Isotope Geochemistry and Mineral Resources, Clausiusstrasse 25, Zurich, 8092, Switzerland
AU: Kleine, T
EM: kleine@erdw.ethz.ch
AF: ETH Zurich, Institue of Isotope Geochemistry and Mineral Resources, Clausiusstrasse 25, Zurich, 8092, Switzerland
AU: Reynolds, B C
EM: reynolds@erdw.ethz.ch
AF: ETH Zurich, Institue of Isotope Geochemistry and Mineral Resources, Clausiusstrasse 25, Zurich, 8092, Switzerland
AB: The superchondritic Mg/Si ratio of the Bulk Silicate Earth (BSE) as compared to chondrites has been a long- standing issue in trying to understand the composition and history of the Earth. It is thought that it must be inherited from the formation or the early differentiation of our planet. The reasons commonly invoked to account for this discrepancy are (i) a relative loss of Si due to its slightly greater volatility relative to Mg; (ii) the production of intra-mantle heterogeneity during magma ocean crystallization, whereby the samples from the upper mantle are actually non-representative of the actual BSE; (iii) lastly, the low Mg/Si of the BSE could be explained by the incorporation of Si in in the Earth's core. We have further investigated this issue by measuring with high precision Si isotopes using the large geometry MC-ICPMS Nu1700 that allows a good resolution of potential isobaric interferences. We have further refined the chemical separation and mass spectrometric technique compared with already published methods. In particular, we have investigated all the steps that could induce isotope fractionation (or produce mass bias) during the fusion technique, chemical separation and mass spectrometry. We have obtained Si isotopic compositions for a series of ordinary and carbonaceous chondrites as well as a suite of peridotites and basalts. Our preliminary results are not identical to the results published by [Georg et al., 2007] and the new implications of our data will be discussed at the meeting. References: R.B. Georg, A.N. Halliday, E.A. Schauble and B.C. Reynolds, "Isotopic evidence for silicon in the Earth's core", Nature, 447, 1102 (2007)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1015 Composition of the core
DE: 1025 Composition of the mantle
DE: 1028 Composition of meteorites (3662, 6240)
DE: 1041 Stable isotope geochemistry (0454, 4870)
SC: Union [U]
MN: 2007 Fall Meeting