Eiler, J. M. and Valley, J. W. and Stolper, E. M. (1997) Stable isotopes in Allan Hills 84001: An ion microprobe study. Meteoritics and Planetary Science, 32 (S4). A38-A38. ISSN 1086-9379. doi:10.1111/j.1945-5100.1997.tb01599.x. https://resolver.caltech.edu/CaltechAUTHORS:20130709-094347673
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Abstract
The temperature of formation of carbonates in ALH 84001 provide a test of the hypothesis that they contain features produced by ancient martian life [1], and contributes to our understanding of the global budgets of martian volatiles. We have determined the micrometer-scale distribution of O and C isotope ratios in carbonate concretions, enstatite, and SiO_2 in ALH 84001 by ion microprobe as a means of constraining the range of possible temperatures of fluid-rock interaction [2]. The principal results are: (1) Carbonate δ^(18)O is 9.5-20.6‰, SMOW, significantly expanding the range from bulk analysis. The magnesite rim is higher in δ^(18)O than Ca-rich (0.07 ≤ X_(ca) ≤ 0.13) cores. (2) Variations in δ^(18)O occur over length scales as small as 50 µm. (3) Interiors of fractured orthopyroxene that hosts carbonate are homogeneous to within ±1‰. (4) Secondary SiO_2 has a δ^(18)O of 20.4‰. These data are inconsistent with mutual O isotope equilibrium among carbonate and silicate minerals and indicate either fine-scale mineral-mineral equilibrium at a range of temperatures ≤ 300°C or a failure to attain mineral-mineral equilibrium. Mineralogical evidence for disequilibrium supports the latter interpretation. Our δ^(18)O values for carbonates have been confirmed by two studies [3], and extended to compositions of carbonate not found in our sample.
Item Type: | Article | |||||||||
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Additional Information: | © 1997 The Meteoritical Society. | |||||||||
Issue or Number: | S4 | |||||||||
DOI: | 10.1111/j.1945-5100.1997.tb01599.x | |||||||||
Record Number: | CaltechAUTHORS:20130709-094347673 | |||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20130709-094347673 | |||||||||
Official Citation: | (1997), Abstracts. Meteoritics & Planetary Science, 32: A5–A147. doi: 10.1111/j.1945-5100.1997.tb01599.x | |||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | |||||||||
ID Code: | 39264 | |||||||||
Collection: | CaltechAUTHORS | |||||||||
Deposited By: | Tony Diaz | |||||||||
Deposited On: | 10 Jul 2013 18:19 | |||||||||
Last Modified: | 09 Nov 2021 23:43 |
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