Leshin, Laurie A. and Epstein, Samuel and Stolper, Edward M. (1996) Hydrogen isotope geochemistry of SNC meteorites. Geochimica et Cosmochimica Acta, 60 (14). pp. 2635-2650. ISSN 0016-7037 http://resolver.caltech.edu/CaltechAUTHORS:20120822-144331289
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We report the yields and hydrogen isotopic compositions of water extracted by stepwise heating of eight whole-rock SNC meteorites. D/H values are consistent with terrestrial water at low temperatures and increase with temperature to values that far exceed terrestrial. The data are consistent with the water in the samples originating from two sources: a terrestrial component/contaminant, released largely at low temperature, and an extraterrestrial component, released at high temperature. The variation in δD values of the high-temperature hydrogen (∼+250 to +900 for the nakhlites, ∼+1200 to +2100 for the shergottites, and ∼+800 for ALH84001) could represent true variation of the δD of the extra-terrestrial water in the samples, or may reflect varying contributions of the terrestrial endmember, even at high temperature. The high δD values are consistent with a martian origin for the meteorites since the current martian atmosphere contains water with a δD of ∼+4000. The presence of alteration products in at least some of the samples suggests the D-enriched water was probably incorporated into the rocks through interaction at low temperature with aqueous crustal fluids that had exchanged with the martian atmosphere. Chassigny contains water that has terrestrial δD values at all temperatures (with the possible exception of the highest temperature step, with δD up to ∼+50), suggesting contamination of this sample by terrestrial water. Carbon and oxygen isotopic results for CO_2 extracted by stepwise heating are also reported. These data are consistent with formation of carbonates in the SNC meteorites by secondary processes on Mars (from fluids that had exchanged C and O with the atmosphere), perhaps in the same alteration events that formed the D-enriched minerals.
|Additional Information:||© 1996 Elsevier Science Ltd. Received 4 October 1995. Accepted 26 March 1996. Available online 24 February 1999. We thank D. Bell, E. Dent, X. Feng, J. Gooding, J. Goris, I. Hutcheon, P. Ihinger, K. McKeegan, S. Nadeau, M. Palin, E. Puris, and G. Rossman for helpful discussions and/or laboratory assistance. Reviews by M. Grady, B. Jakosky, K. McKeegan, and A. Treiman improved the manuscript and are appreciated. We specifically acknowledge E. Paris and G. Parodi for assistance in obtaining the Govemador Valadares sample. We also thank the following for providing samples for this study: D. Bell, Carnegie Institution of Washington; G. Cavaretta, Universita "La Sapienza"; The Geological Survey of Nigeria; M. Grady, Natural History Museum, London; G. MacPherson, Smithsonian Institution; E. Olsen, Field Museum of Natural History; C. Perron and B. Zanda, Muséum National D'Histoire Naturelle; R. Score and M. Lindstrom, Johnson Space Center. Supported by a Corning Glass Works Graduate Fellowship and NASA Graduate Student Research Program grant NGT 50800 to L.A.L., NASA grants NAG 9-105 and NAGW 3533 to E.M.S., and NAG 9-46 and NAGW 3329 to S.E. Contribution number 5600, Division of Geological and Planetary Sciences, California Institute of Technology. Editorial handling: G. Crozaz.|
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|Official Citation:||Laurie A. Leshin, Samuel Epstein, Edward M. Stolper, Hydrogen isotope geochemistry of SNC meteorites, Geochimica et Cosmochimica Acta, Volume 60, Issue 14, July 1996, Pages 2635-2650, ISSN 0016-7037, 10.1016/0016-7037(96)00122-6. (http://www.sciencedirect.com/science/article/pii/0016703796001226)|
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|Deposited On:||22 Aug 2012 22:04|
|Last Modified:||22 Aug 2012 22:04|
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