Ancient volcanism on the Moon: Insights from Pb isotopes in the MIL 13317 and Kalahari 009 lunar meteorites

Joshua F. Snape*, Natalie M. Curran, Martin J. Whitehouse, Alexander A. Nemchin, Katherine H. Joy, Tom Hopkinson, Mahesh Anand, Jeremy J. Bellucci, Gavin G. Kenny

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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Abstract

Lunar meteorites provide a potential opportunity to expand the study of ancient (>4000 Ma) basaltic volcanism on the Moon, of which there are only a few examples in the Apollo sample collection. Secondary Ion Mass Spectrometry (SIMS) was used to determine the Pb isotopic compositions of multiple mineral phases (Ca-phosphates, baddeleyite K-feldspar, K-rich glass and plagioclase) in two lunar meteorites, Miller Range (MIL) 13317 and Kalahari (Kal) 009. These data were used to calculate crystallisation ages of 4332±2 Ma (95% confidence level) for basaltic clasts in MIL 13317, and 4369±7 Ma (95% confidence level) for the monomict basaltic breccia Kal 009. From the analyses of the MIL 13317 basaltic clasts, it was possible to determine an initial Pb isotopic composition of the protolith from which the clasts originated, and infer a 238U/204Pb ratio (μ-value) of 850±130 (2σ uncertainty) for the magmatic source of this basalt. This is lower than μ-values determined previously for KREEP-rich (an acronym for K, Rare Earth Elements and P) basalts, although analyses of other lithological components in the meteorite suggest the presence of a KREEP component in the regolith from which the breccia was formed and, therefore, a more probable origin for the meteorite on the lunar nearside. It was not possible to determine a similar initial Pb isotopic composition from the Kal 009 data, but previous studies of the meteorite have highlighted the very low concentrations of incompatible trace elements and proposed an origin on the farside of the Moon. Taken together, the data from these two meteorites provide more compelling evidence for widespread ancient volcanism on the Moon. Furthermore, the compositional differences between the basaltic materials in the meteorites provide evidence that this volcanism was not an isolated or localised occurrence, but happened in multiple locations on the Moon and at distinct times. In light of previous studies into early lunar magmatic evolution, these data also imply that basaltic volcanism commenced almost immediately after Lunar Magma Ocean (LMO) crystallisation, as defined by Nd, Hf and Pb model ages at about 4370 Ma.

Original languageEnglish
Pages (from-to)84-95
Number of pages12
JournalEarth and Planetary Science Letters
Volume502
Early online date12 Sept 2018
DOIs
Publication statusPublished - 15 Nov 2018

Funding

We thank NASA Johnson Space Center for the loan of MIL 13317 and acknowledge the efforts of the ANSMET in collecting the sample. Addi Bischoff is thanked for loaning the polished sections of Kalahari 009. The manuscript benefitted from two anonymous reviews and the editorial handling of Frederic Moynier. This work was primarily funded by grants from the Knut and Alice Wallenberg Foundation ( 2012.0097 ) and the Swedish Research Council ( VR 621-2012-4370 ) to MJW and AAN. JFS acknowledges funding from the European Commission Horizon 2020 Research and Innovation programme, through a Marie Skłodowska-Curie Actions Fellowship grant ( 794287 ). KHJ acknowledges Royal Society grant RS/UF140190 and STFC grants ST/M001253/1 and ST/R000751/1 . NC was funded by an STFC studentship. MA acknowledges funding from Science and Technology Facilities Council (STFC) grants ST/L000776/1 and ST/P000657/1 . JJB acknowledges from the Swedish Research Council ( VR 2016-03371 ). At the time of the analytical work, the NordSIMS facility was operated as part of a Swedish–Icelandic infrastructure; this is NordSIMS publication #571. The research has made use of NASA's Astrophysics Data System. Appendix

FundersFunder number
European Commission Horizon 2020
Horizon 2020 Framework Programme794287
H2020 Marie Skłodowska-Curie Actions
Science and Technology Facilities CouncilST/P000657/1, ST/L000776/1, VR 2016-03371, ST/M001253/1, ST/R000751/1
Royal SocietyRS/UF140190
European Commission
Knut och Alice Wallenbergs Stiftelse2012.0097
VetenskapsrådetVR 621-2012-4370

    Keywords

    • Kalahari 009
    • lunar basalt
    • lunar meteorites
    • lunar volcanism
    • MIL 13317
    • Pb isotopes

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