Sulfur isotopic composition of Fe‐Ni sulfide grains in CI and CM carbonaceous chondrites |
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| Authors: | Emma S BULLOCK Kevin D McKEEGAN Matthieu GOUNELLE Monica M GRADY Sara S RUSSELL |
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| Institution: | 1. Department of the Geophysical Sciences, University of Chicago, 5734 S. Ellis Avenue, Chicago, Illinois 60637, USA;2. Present address: Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia 20560, USA;3. Department of Earth and Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East, Los Angeles, California 90095–1567, USA;4. Laboratoire de Minéralogie et Cosmochimie du Muséum (LMCM), CNRS & Muséum National d’Histoire Naturelle, UMR 7202, 57 rue Cuvier, 75005 Paris, France;5. The Open University, Walton Hall, Milton Keynes MK7 7AA, UK;6. Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK |
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| Abstract: | Abstract– In situ secondary ion mass spectrometry analyses of 32S, 33S, and 34S in iron‐nickel sulfide grains in two CI1 chondrites and six CM chondrites were performed. The results show a wider range of both enrichment and depletion in δ34S relative to troilite from the Canyon Diablo meteorite (CDT) than has been observed in previous studies. All data points lie within error of a single mass dependent fractionation line. Sulfides from CI1 chondrites show δ34SCDT from ?0.7 to 6.8‰, while sulfide grains in the CM1 chondrite are generally depleted in heavy sulfur relative to CDT (δ34S from ?2.9 to 1.8‰). CM2 chondrites contain sulfide grains that show enrichment and depletion in 34S (δ34SCDT from ?7.0 to 6.8‰). Sulfates forming from sulfide grains during aqueous alteration on the chondrite parent body are suggested to concentrate light sulfur, leaving the remaining sulfide grains enriched in the heavy isotopes of sulfur. The average degree of enrichment in 34S in CM chondrite sulfides is broadly consistent with previously suggested alteration sequences. |
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