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The chlorine isotope fingerprint of the lunar magma ocean

Boyce, Jeremy W. and Treiman, Allan H. and Guan, Yunbin and Ma, Chi and Eiler, John M. and Gross, Juliane and Greenwood, James P. and Stolper, Edward M. (2015) The chlorine isotope fingerprint of the lunar magma ocean. Science Advances, 1 (8). Art. No. e1500380. ISSN 2375-2548. PMCID PMC4643783. doi:10.1126/sciadv.1500380.

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The Moon contains chlorine that is isotopically unlike that of any other body yet studied in the Solar System, an observation that has been interpreted to support traditional models of the formation of a nominally hydrogen-free (“dry”) Moon. We have analyzed abundances and isotopic compositions of Cl and H in lunar mare basalts, and find little evidence that anhydrous lava outgassing was important in generating chlorine isotope anomalies, because ^(37)Cl/^(35)Cl ratios are not related to Cl abundance, H abundance, or D/H ratios in a manner consistent with the lava-outgassing hypothesis. Instead, ^(37)Cl/^(35)Cl correlates positively with Cl abundance in apatite, as well as with whole-rock Th abundances and La/Lu ratios, suggesting that the high ^(37)Cl/^(35)Cl in lunar basalts is inherited from urKREEP, the last dregs of the lunar magma ocean. These new data suggest that the high chlorine isotope ratios of lunar basalts result not from the degassing of their lavas but from degassing of the lunar magma ocean early in the Moon’s history. Chlorine isotope variability is therefore an indicator of planetary magma ocean degassing, an important stage in the formation of terrestrial planets.

Item Type:Article
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URLURL TypeDescription CentralArticle
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:© 2015 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited. Submitted 23 March 2015; Accepted 31 July 2015; Published 25 September 2015. We are grateful to the institutions and people who made samples available for this research, including the Lunar Sample and Meteorite curators at the Johnson Space Center, and T. Bunch of Northern Arizona University. We are also grateful to F. McCubbin and J. Mosenfelder, who graciously provided apatite and other mineral standard materials, and M. Le Voyer, who was instrumental in developing Cl isotope capabilities at Caltech. The first author would like to acknowledge the support that he received from his coauthors and colleagues during the duration of this project, which was considerably lengthened by a near-fatal illness. The manuscript benefitted from detailed, thoughtful, and constructive criticism from the editor, two anonymous reviewers, and C. Neal - who is perhaps thanked twice in this sentence. Funding: This research was supported by NASA Early Career Fellowships to J.W.B. (NNX13AG40G) and J.G. (NNX13AF54G), as well as NASA grants to A.H.T. (NNX12AH64G) and J.P.G. (NNX11AB29G). Author contributions: J.W.B., A.H.T., J.M.E., and E.M.S. conceived the project. C.M., A.H.T., and J.G. performed the petrographic and petrologic descriptions. Y.G., C.M., A.H.T., and J.W.B. performed the analyses. All authors participated in the data reduction and writing of the manuscript. Competing interests: The authors declare that they have no competing interests. Data and materials availability: All new data generated for this paper are found in Table 1. Samples analyzed were borrowed from several sources (see above) and must be requested directly to those sources.
Funding AgencyGrant Number
Subject Keywords:Moon, Lunar, volatiles, apatite, basalt, chlorine, water, magma ocean
Issue or Number:8
PubMed Central ID:PMC4643783
Record Number:CaltechAUTHORS:20151221-083226607
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Official Citation:The chlorine isotope fingerprint of the lunar magma ocean BY JEREMY W. BOYCE, ALLAN H. TREIMAN, YUNBIN GUAN, CHI MA, JOHN M. EILER, JULIANE GROSS, JAMES P. GREENWOOD, EDWARD M. STOLPER SCIENCE ADVANCES25 SEP 2015 : E1500380
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63090
Deposited By: Tony Diaz
Deposited On:22 Dec 2015 20:27
Last Modified:10 Nov 2021 23:11

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