TY - JOUR
T1 - Terrestrial alteration of carbonate in a suite of Antarctic CM chondrites
T2 - Evidence from oxygen and carbon isotopes
AU - Tyra, M. A.
AU - Farquhar, J.
AU - Wing, B. A.
AU - Benedix, G. K.
AU - Jull, A. J.T.
AU - Jackson, T.
AU - Thiemens, M. H.
N1 - Funding Information:
This research was supported by the NASA Cosmochemistry program (J.F.), and the NASA Exobiology Program (J.F.). This work was partially supported by NASA Cosmochemistry Grant NAG5-11979 and NSF Grant EAR01-15488. The work was also supported by GRB award of the University of Maryland. The authors also thank Phil Piccoli, Tim McCoy, Linda Welzenbach, Lori Hewitt, and Alex Leonard for their help with this project. We also thank Matthieu Gounelle, Mikhail Zolotov, the AE, and an anonymous reviewer for contributing comments that improved the manuscript.
PY - 2007/2/1
Y1 - 2007/2/1
N2 - The oxygen (δ18O, δ17O) and carbon (δ13C, FMOD14C-the fraction of modern 14C) isotopic compositions of carbonate were measured for a set of paired Antarctic CM chondrites (EET 96006, EET 96016, EET 96017, and EET 96019). While the oxygen isotopic compositions do not plot on the terrestrial fractionation line and indicate that a component of the carbonate minerals has an extraterrestrial origin, they also do not fall on the array defined for carbonates by CM falls and are thus consistent with the presence of a terrestrial carbonate component. The δ13C and FMOD14C measurements of carbonate suggest the presence of at least two carbon sources: carbonate derived from atmospheric CO2 that is inferred to have been produced as a result of silicate weathering reactions and carbonate derived from another carbon source that is either old or non-atmospheric. The relationships between oxygen and carbon isotope data provide additional constraints on the weathering process, and allow the possibility that rock-dominated weathering of the meteorite caused the oxygen isotopic composition of Antarctic water added to the meteorite to evolve away from the terrestrial mass-fractionation array, leading to formation of low temperature terrestrial alteration products that do not lie on the terrestrial fractionation line.
AB - The oxygen (δ18O, δ17O) and carbon (δ13C, FMOD14C-the fraction of modern 14C) isotopic compositions of carbonate were measured for a set of paired Antarctic CM chondrites (EET 96006, EET 96016, EET 96017, and EET 96019). While the oxygen isotopic compositions do not plot on the terrestrial fractionation line and indicate that a component of the carbonate minerals has an extraterrestrial origin, they also do not fall on the array defined for carbonates by CM falls and are thus consistent with the presence of a terrestrial carbonate component. The δ13C and FMOD14C measurements of carbonate suggest the presence of at least two carbon sources: carbonate derived from atmospheric CO2 that is inferred to have been produced as a result of silicate weathering reactions and carbonate derived from another carbon source that is either old or non-atmospheric. The relationships between oxygen and carbon isotope data provide additional constraints on the weathering process, and allow the possibility that rock-dominated weathering of the meteorite caused the oxygen isotopic composition of Antarctic water added to the meteorite to evolve away from the terrestrial mass-fractionation array, leading to formation of low temperature terrestrial alteration products that do not lie on the terrestrial fractionation line.
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U2 - 10.1016/j.gca.2006.10.023
DO - 10.1016/j.gca.2006.10.023
M3 - Article
AN - SCOPUS:33846331673
SN - 0016-7037
VL - 71
SP - 782
EP - 795
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 3
ER -