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The formation of weathering products on the LEW 85320 ordinary chondrite - Evidence from carbon and oxygen stable isotope compositions and implications for carbonates in SNC meteoritesIsotopic analysis of nesquehonite recovered from the surface of the LEW 85320 H5 ordinary chondrite shows that the delta C-13 and delta O-18 values of the two generations of bicarbonate (Antarctic and Texas) are different: delta C-13 = + 7.9 per mil and + 4.2 per mil; delta O-18 = + 17.9 per mil and + 12.1 per mil, respectively. Carbon isotopic compositions are consistent with equilibrium formation from atmospheric carbon dioxide at - 2 + or - 4 C (Antarctic) and + 16 + or - 4 C (Texas). Oxygen isotopic data imply that the water required for nesquehonite precipitation was derived from atmospheric water vapor or glacial meltwater which had locally exchanged with silicates, either in the meteorite or in underlying bedrock. Although carbonates with similar delta C-13 values have been identified in the SNC meteorites EETA 79001 and Nakhla, petrographic and temperature constraints argue against their simply being terrestrial weathering products.
Document ID
19890056992
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Grady, Monica M.
(Open Univ. Milton Keynes, United Kingdom)
Wright, I. P.
(Open Univ. Milton Keynes, United Kingdom)
Pillinger, C. T.
(Open University Milton Keynes, United Kingdom)
Gibson, E. K., Jr.
(NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 14, 2013
Publication Date
March 1, 1989
Publication Information
Publication: Meteoritics
Volume: 24
ISSN: 0026-1114
Subject Category
Lunar And Planetary Exploration
Accession Number
89A44363
Distribution Limits
Public
Copyright
Other

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