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D-poor hydrogen in lunar mare basalts assimilated from lunar regolith

Treiman, Allan H. and Boyce, Jeremy W. and Greenwood, James P. and Eiler, John M. and Gross, Juliane and Guan, Yunbin and Ma, Chi and Stolper, Edward M. (2016) D-poor hydrogen in lunar mare basalts assimilated from lunar regolith. American Mineralogist, 101 (7). pp. 1596-1603. ISSN 0003-004X. https://resolver.caltech.edu/CaltechAUTHORS:20160708-101905095

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Abstract

Apatite grains in lunar mare basalts contain hydrogen that ranges in D/H ratio by more than a factor of two. For most of these basalts, the D/H ratios in their apatite grains decrease with measures of the host basalts’ time spent at elevated temperature, specifically the Fe-Mg homogenization of their pyroxenes. Most basalts with homogeneous pyroxenes (i.e., with constant Fe/Mg ratio) have apatite grains with low D/H (δD ≈ −100‰), whereas most basalts with heterogeneous pyroxenes (i.e., varying or zoned Fe/Mg) have apatite with high D/H (δD up to ~ +1100‰). This relationship suggests that low D/H values were acquired during thermal processing, i.e., during Fe-Mg chemical equilibration, during or after emplacement. This light hydrogen is likely derived from solar wind implanted into the lunar regolith (with δD from −125‰ to −800‰), and could enter basalts either by assimilation of regolith or by vapor transport from regolith heated by the flow. If a basalt could not interact with regolith rich in solar wind (e.g., it was emplaced onto other fresh basalts), its apatite could retain a magmatic D/H signature. The high D/H component (in the apatites of unequilibrated basalts) is most reasonably that indigenous magmatic hydrogen, i.e., representing hydrogen in the basalt’s source mantles, or magmatic hydrogen that was residual after partial degassing of H_2.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.2138/am-2016-5582DOIArticle
http://ammin.geoscienceworld.org/content/101/7/1596PublisherArticle
http://www.minsocam.org/MSA/AmMin/TOC/2016/Jul2016_data/AM-16-75582.zipPublisherSupplemental Material
ORCID:
AuthorORCID
Treiman, Allan H.0000-0002-8073-2839
Guan, Yunbin0000-0002-7636-3735
Ma, Chi0000-0002-1828-7033
Stolper, Edward M.0000-0001-8008-8804
Additional Information:© 2016 Mineralogical Society of America. Manuscript received October 6, 2015; Manuscript accepted March 9, 2016; First Published on July 01, 2016. Manuscript handled by Ian Swainson. All data generated for this study are available in the online deposit material2. The second author acknowledges support received from coauthors and colleagues during this project, which was considerably lengthened by a near-fatal illness. We are grateful to the institutions and people who made samples available for his research, including the Lunar Sample and Meteorite curators at Johnson Space Center; F. McCubbin and J. Mosenfelder, who provided apatite and other mineral standard materials; and K. Joy for valuable discussions. The manuscript was improved substantially by reviews, especially that by R. Tartése, to whom we are particularly grateful; we also thank five anonymous reviewers. This research was supported by NASA Early Career Fellowships to Boyce (NNX13AG40G), as well as NASA grants to Treiman and Gross (NNX12AH64G) and Greenwood (NNX11AB29G). The authors have no competing interests. LPI Contribution 1913.
Funders:
Funding AgencyGrant Number
NASANNX13AG40G
NASANNX12AH64G
NASANNX11AB29G
Subject Keywords:Mare basalt, hydrogen isotopes, lunar regolith
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Lunar and Planetary Institute1913
Issue or Number:7
Record Number:CaltechAUTHORS:20160708-101905095
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160708-101905095
Official Citation:D-poor hydrogen in lunar mare basalts assimilated from lunar regolith Allan H. Treiman, Jeremy W. Boyce, James P. Greenwood, John M. Eiler, Juliane Gross, Yunbin Guan, Chi Ma, Edward M. Stolper American Mineralogist Jul 2016, 101 (7) 1596-1603; DOI: 10.2138/am-2016-5582
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:68918
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 Jul 2016 23:50
Last Modified:27 Nov 2019 00:18

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