A contribution to the stable carbon isotope geochemistry of iron meteorites |
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| Authors: | Peter Deines Frans E Wickman |
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| Institution: | Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania 16802, U.S.A. |
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| Abstract: | For most iron meteorites studied, the carbon isotopic composition of nodular graphite falls in the range ?4.8 to ?8.2%. vs PDB and shows a mode between ?5 and ?6%.. Fourteen cohenite analyses from the Magura meteorite fall between ?18.1 and ?19.2%. with a pronounced clustering around ?18.5%.. Carbon of a taenite separate from the same meteorite has an isotopic composition of ?18.8%.; compositions between ?19.7 and ?22.1%. were found for taenite carbon in five other octahedrites. It is suggested that the 12C enrichment in cohenite and taenite relative to the nodular graphite is a general phenomenon in iron meteorites, and that the study of 13C abundances in iron meteorites may aid in the elucidation of their history. To this end an experimental study of carbon isotope fractionations in the system Fe-Ni-C is essential. The 13C content of carbon from several silicate inclusions in the Four Corners and ‘El Taco’ (Campo del Cielo) meteorites is generally similar to the nodular graphite, the 12C enrichment (?13%.) in one specimen may be interpreted in terms of a mixing model involving an original inclusion carbon and carbon exsolved from the taenite upon cooling. |
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