LOOKING FOR THE CARRIER PHASE OF Cr IN THE CARBONACEOUS CHONDRITE ORGUEIL
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چکیده
Introduction: 54 Cr anomalies are widely distributed in inner Solar System materials [1-6]. These variations have been attributed to nucleosynthetic effects. Astronomical models predict that 54 Cr, along with other neutron-rich nuclides, such as 50 Ti, are produced in a neutron-rich environment at or near nuclear statistical equilibrium in both Type Ia and Type II supernovae [7,8]. Further constraints on the nucleosynthetic source of 54 Cr largely rely on the identification of the carrier phase. Isolating and identifying the carrier phase of 54 Cr anomalies is an outstanding problem in cosmochemistry. We have recently started to search for the carrier phase by in-situ NanoSIMS analyses of a residue separated from the C1 chondrite Orgueil. Methods: The original CsF/HCl Orgueil residue was ashed in an O-plasma to remove C. The remaining minerals were dispersed as a liquid suspension onto a gold substrate. A quick SEM examination of the mount shows that the mineral assemblage includes mostly sub-micron chromite and Cr-rich spinel, and a small amount of SiC. Isotope measurements were made on a Cameca NanoSIMS 50L in multi-collection mode at the Carnegie Institution. A 0.5-0.7 μm, O-primary ion beam of
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تاریخ انتشار 2009