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Various lines of evidence suggest that material isotopically similar to enstatite chondrites may have accreted to the terrestrial planets. However, the enrichment of light Si isotopes in bulk enstatite chondrites is not easy to reconcile with the heavy Si isotopic composition of the Bulk Silicate Earth (BSE). To investigate the origin of the light Si isotopic composition of enstatite chondrites, we have obtained in-situ Si isotope data and simultaneously major-and trace element data in silicate and metal phases of chondrules, a metal-troilite spherule, and matrix from the enstatite chondrites Sahara 97072 (EH3) and Indarch (EH4) using laser ablation split stream-ICP-MS, which combines femto-second LA-MC-ICP-MS and Quadrupole-ICP-MS. Silicates in chondrules show variations in δ 30 Si (‰ variations of 30 Si/ 28 Si relative to NBS-28) ranges from-1.06 ± 0.13‰ (2 S.E.) to-0.38 ± 0.11‰. δ 30 Si in matrix silicates ranges from-0.96 ± 0.18‰ to-0.22 ± 0.12‰. The δ 30 Si-value of silicate phases varies independently of Mg/Si, ruling out simple equilibrium condensation from nebular gas. Some silicates in both enstatite chondrites have δ 30 Si-values like CI chondrites, whereas Si in other silicates is isotopically lighter, suggesting that the precursor materials of EH chondrites were already depleted in heavy Si isotopes. The metal phases in the matrix show average δ 30 Si of-6.0 ± 0.6‰. In spite of different metamorphic grades, the fractionation of Si isotopes between matrix metal and silicates in Sahara 97072 and Indarch shows no systematic differences, and thus no re-equilibration of Si 2 isotopes occurred between silicates and metal at metamorphic temperatures below 900 K. The δ 30 Si-value of metal from a metal-troilite spherule from Sahara 97072 (-8.24 ± 0.12‰) is lower than that of matrix metals. These differences were likely inherited from different formation environments of matrix-and spherule metal. If metal formation occurred under equilibrium conditions, then matrix metal may have formed at higher temperatures than the MTS metal. or at similar temperatures but slightly lower oxygen fugacities, or the MTS metal equilibrated with gas or silicates which were not incorporated into EH chondrites because they were lost from the EH chondrite formation region. Alternatively, the differences in δ 30 Si of different metals could also reflect variable kinetic isotope fractionation during the formation of metal and exsolution of perryite. The considerably lower δ 30 Si-values of bulk EH chondrites compared to CI-and other chondrites partly reflects the presence of Si bearing metal with isotopically light Si and partly silicates with isotopically light Si. The latter indicate loss of a heavy Si-rich silicate component from the EH3 formation region, presumably together with refractory elements. Although the Si isotopic composition of bulk EH chondrites precludes that these represent major building material of the Earth, the combination of complementary heavy Si isotope-and refractory element-enriched reduced materials and ca...

The 187 Re-187 Os systematics, abundances of highly siderophile elements (HSE: Re, platinum group elements and Au), Te, Se and S as well as major and minor elements were determined in separated components of two unequilibrated L chondrites QUE 97008 (L3.05) and Ceniceros (L3.7). The 187 Re-187 Os systematics are disturbed in the components of both meteorites, most likely due to open system behaviour of Re during terrestrial weathering of QUE 97008 and alteration on the L chondrite parent body as indicated by an internal errorchron generated for components of Ceniceros. The HSE abundance patterns suggest that the bulk rock abundances were mainly controlled by two different end members. Non-magnetic fractions display lower Re/Os and HSE/Ir than CI chondrites. Chondrules, metal-troilite spherules and fine magnetic fractions, are depleted in refractory HSE and show higher Rh/Ir, Pd/Ir and Au/Ir than in CI chondrites. The different HSE compositions indicate the presence of unequilibrated alloys and loss of refractory HSE-rich carrier phases from the precursors of some L chondrite components. Gold is decoupled from other HSE in magnetic fractions and shows chalcophile affinities with a grain size dependent variation similar to S and Se, presumably inherited from preaccretionary processes. Tellurium is depleted in all components compared to other analysed siderophile elements, and its abundance was most likely controlled by fractional condensation and different geochemical affinities. The volatility dependent depletion of Te requires different physical and chemical conditions than typical for the canonical condensation sequence as represented by carbonaceous chondrites. Tellurium also shows variable geochemical behaviour, siderophile in Ceniceros, predominantly chalcophile in QUE 97008. These differences may have been inherited from element partitioning during chondrule formation. Selenium and S on the other hand are almost unfractionated from each other and only show complementary S/Se in a few components, presumably due to the effects of volatility or metal-silicate partitioning during chondrule formation. Terrestrial weathering had negligible effects on the S, Se and Te systematics. The unequilibrated ordinary chondrites (UOC) are some of the most primitive rocks in the solar system (Nagahara, 1984; Alexander et al., 1990). They are composed of components such as different sized chondrules, matrix, Fe-Ni metal and, more rarely, refractory inclusions (Scott and Krot, 2003). These components were formed in different chemical and physical environments in the solar nebula (Larimer and Anders, 1967, 1970; Huss et al., 2001). The components show a diversity in elemental and isotopic compositions suggesting that they underwent fractionation processes in the

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Abstract-187 Os systematics, abundances of highly siderophile elements (HSE: Re, PGE, and Au), chalcogen elements (Te, Se, and S), and some major and minor elements were determined in physically separated components of the Allende (CV3) and Murchison (CM2) carbonaceous chondrites. Substantial differences exist in the absolute and relative abundances of elements in the components, but the similarity of calculated and literature bulk rock abundances of HSE and chalcogens indicate that chemical complementarity exists among the components, with CI chondrite-like ratios for many elements. Despite subsequent alteration and oxidation, the overall cosmochemical behavior of most moderately to highly siderophile elements during high-temperature processing has been preserved in components of Allende at the sampling scale of the present study. The 187 Re-187 Os systematics and element variations of Allende are less disturbed compared with Murchison, which reflects different degrees of oxidation and alteration of these meteorites. The HSE systematics (with the exception of Au) is controlled by two types of materials: Pd-depleted condensates and CI chondrite-like material. Enrichment and heterogeneous distribution of Au among the components is likely the result of hydrothermal alteration. Chalcogen elements are depleted compared with HSE in all components, presumably due to their higher volatility. Small systematic variations of S, Se, and Te in components bear the signature of fractional condensation/partial evaporation and metal-sulfide-silicate partitioning.