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Impact-induced devolatilization and hydrogen isotopic fractionation of serpentine: Implications for planetary accretion

Tyburczy, James A. and Krishnamurthy, R. V. and Epstein, Samuel and Ahrens, Thomas J. (1990) Impact-induced devolatilization and hydrogen isotopic fractionation of serpentine: Implications for planetary accretion. Earth and Planetary Science Letters, 98 (2). pp. 245-260. ISSN 0012-821X. https://resolver.caltech.edu/CaltechAUTHORS:20130820-110805297

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Abstract

The degree of impact-induced devolatilization of nonporous serpentine, porous serpentine, and deuterium-enriched serpentine was investigated using two independent experimental methods, the gas recovery method and the solid recovery method, yielding consistent results. The gas recovery method enables determination of the chemical and hydrogen isotopic composition of the recovered gases. Experiments on deuterium-enriched serpentine unambiguously identify the samples as the source of the recovered gases, as opposed to other possible contaminants. For shock pressures near incipient devolatilization (P_(initial) = 5.0 GPa), the hydrogen isotopic composition of the evolved gas is similar to that of the starting material. For higher shock pressures the bulk evolved gas is significantly lower in deuterium than the starting material. There is also significant reduction of H_2O to H_2 in gases recovered at higher shock pressures, probably caused by reaction of evolved H_2O with the metal gas recovery fixture. The hydrogen isotopic fractionation between the evolved gas and the residual solid indicates nonequilibrium, kinetic control of gas-solid isotopic ratios. In contrast, gaseous H_2O-H_2 isotopic fractionation suggests high temperature (800–1300 K) isotopic equilibrium between the gaseous species, indicating initiation of devolatilization at sites of greater than average energy deposition (i.e., shear bands). Impact-induced hydrogen isotopic fractionation of hydrous silicates during accretion can affect the distribution of hydrogen isotopes of planetary bodies during accretion, leaving the interiors enriched in deuterium. The significance of this process for planetary development depends on the models used for extrapolation of the observed isotopic fractionation to devolatilizations greater than those investigated experimentally and assumptions about timing and rates of protoatmosphere loss, frequency of multiple impacts, and rates of gas-solid or gas-melt isotopic re-equilibration. A simple model indicates that substantial planetary interior enrichments of D/H relative to that of the incident material can result from impact-induced hydrogen fractionation during accretion.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/0012-821X(90)90063-4DOIArticle
http://www.sciencedirect.com/science/article/pii/0012821X90900634PublisherArticle
Additional Information:© 1990 Elsevier Science Publishers B.V. Received September 5, 1989; accepted for publication January 26, 1990. We thank Professor George Rossman for the use of his laboratory facilities. E. Gelle, M. Long, and C. Manning provided expert experimental assistance. The manuscript was greatly improved by comments from anonymous reviewers. Supported under NASA grants NGL-05-002-105 and NAG9-46. Caltech Division of Geological and Planetary Sciences contribution no. 4516.
Funders:
Funding AgencyGrant Number
NASANGL-05-002-105
NASANAG9-46
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences 4516
Issue or Number:2
Record Number:CaltechAUTHORS:20130820-110805297
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130820-110805297
Official Citation:James A. Tyburczy, R.V. Krishnamurthy, Samuel Epstein, Thomas J. Ahrens, Impact-induced devolatilization and hydrogen isotopic fractionation of serpentine: Implications for planetary accretion, Earth and Planetary Science Letters, Volume 98, Issue 2, May 1990, Pages 245-261, ISSN 0012-821X, http://dx.doi.org/10.1016/0012-821X(90)90063-4.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40736
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:27 Aug 2013 17:25
Last Modified:03 Oct 2019 05:42

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