Abundances of highly siderophile elements (HSE: Re, Os, Ir, Ru, Pt, Rh, Pd and Au), chalcogen elements (S, Se and Te) and Os isotopic composition in components of chondrites are important to constrain the element fractionation processes in the early solar nebula, alteration processes on the meteorite parent bodies and later element fractionation processes during terrestrial weathering in case of meteorite finds. All components of the EH chondrites show higher Au/HSE compared to CI and other

more »

... drites. The history of the components of EH chondrites is complex and involves early fractional condensation and loss of refractory element rich phases, subsequent condensation of moderately volatile elements in a highly reduced environmentwith partly chalcophile behavior of Au during this stage and melting, evaporation and recondensation of metal grains in sulfur rich environments. Primary variations of the HSE abundances and ratios in the components of carbonaceous chondrites were overprinted by the parent body alteration processes. Fractional condensation and isolation of refractory metal alloys was a major early process, responsible for the element variation in carbonaceous chondrites. Some refractory metal alloys were trapped in silicates and occur in nonmagnetic fractions. A Pd depleted component occurs in themajor HSE carrier phases present in the Allende and Murchison. This component is either the product of fractional condensation (the complementary Pd rich component is missing) or resulted from the evaporation of Pd during high temperature processing of metal. Gold is heterogeneously distributed in different splits of the Allende and Murchison bulk rocks. Components of Murchison show similar heterogeneous distribution of Au, which was likely caused by aqueous alteration. In case of Allende linear correlations of siderophile and chalcophile elements (Te-Se, S-Se, Ni/Fe-Co/Fe and Au-Pd) in the components suggest that the chemical variations reflect mixing of components with compositions affected by preaccretionary [...]