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Cryogenic Calcite: A Morphologic and Isotopic Analog to the ALH84001 CarbonatesMartian meteorite ALH84001 carbonates preserve large and variable microscale isotopic compositions, which in some way reflect their formation environment. These measurements show large variations (>20%) in the carbon and oxygen isotopic compositions of the carbonates on a 10-20 micron scale that are correlated with chemical composition. However, the utilization of these data sets for interpreting the formation conditions of the carbonates is complex due to lack of suitable terrestrial analogs and the difficulty of modeling under non-equilibrium conditions. Thus, the mechanisms and processes are largely unknown that create and preserve large microscale isotopic variations in carbonate minerals. Experimental tests of the possible environments and mechanisms that lead to large microscale isotopic variations can help address these concerns. One possible mechanism for creating large carbon isotopic variations in carbonates involves the freezing of water. Carbonates precipitate during extensive CO2 degassing that occurs during the freezing process as the fluid s decreasing volume drives CO2 out. This rapid CO2 degassing results in a kinetic isotopic fractionation where the CO2 gas has a much lighter isotopic composition causing an enrichment of 13C in the remaining dissolved bicarbonate. This study seeks to determine the suitability of cryogenically formed carbonates as analogs to ALH84001 carbonates. Specifically, our objective is to determine how accurately models using equilibrium fractionation factors approximate the isotopic compositions of cryogenically precipitated carbonates. This includes determining the accuracy of applying equilibrium fractionation factors during a kinetic process, and determining how isotopic variations in the fluid are preserved in microscale variations in the precipitated carbonates.
Document ID
20040056049
Document Type
Conference Paper
Authors
Niles, P. B. (Arizona State Univ. Tempe, AZ, United States)
Leshin, L. A. (Arizona State Univ. Tempe, AZ, United States)
Socki, R. A. (NASA Johnson Space Center Houston, TX, United States)
Guan, Y. (Arizona State Univ. Tempe, AZ, United States)
Ming, D. W. (NASA Johnson Space Center Houston, TX, United States)
Gibson, E. K. (NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Publication Information
Publication: Lunar and Planetary Science XXXV: Martian Meteorites: Hot and Steamy
Subject Category
Lunar and Planetary Science and Exploration
Distribution Limits
Public
Copyright
Public Use Permitted.

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IDRelationTitle20040056046Analytic PrimaryLunar and Planetary Science XXXV: Martian Meteorites: Hot and Steamy
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