Timing of geological events in the lunar highlands recorded in shocked zircon-bearing clasts from Apollo 16

Katherine H. Joy*, J.F. Snape, A.A. Nemchin, R. Tartèse, D.M. Martin, Martin J. Whitehouse, V. Vishnyakov, John F. Pernet-Fisher, D.A. Kring

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Apollo 16 soil-like regolith breccia 65745,7 contains two zircon-bearing clasts. One of these clasts is a thermally annealed silica-rich rock, which mineralogically has affinities with the High Alkali Suite (Clast 1), and yields zircon dates ranging from 4.08 to 3.38 Ga. The other clast is a KREEP-rich impact melt breccia (Clast 2) and yields zircon dates ranging from 3.97 to 3.91 Ga. The crystalline cores of both grains, which yield dates of ca 3.9 Ga, have undergone shock pressure modification at less than 20 GPa. We interpret that the U-Pb chronometer in these zircon grains has been partially reset by the Imbrium basin-forming event when the clasts were incorporated into the Cayley Plains ejecta blanket deposit. The zircon grains in Clast 1 have been partially decomposed, resulting in a breakdown polymineralic texture, with elevated U, Pb and Th abundances compared with those in the crystalline zircon. These decomposed areas exhibit younger dates around 3.4 Ga, suggesting a secondary high-pressure, high-temperature event, probably caused by an impact in the local Apollo 16 highlands area.
Original languageEnglish
Article number200236
Pages (from-to)1-21
Number of pages21
JournalRoyal Society Open Science
Volume7
Issue number6
Early online date3 Jun 2020
DOIs
Publication statusPublished - Jun 2020

Funding

Data accessibility. Data have been uploaded as part of the electronic supplementary material. Authors’ contributions. K.H.J. conceived the study and wrote the manuscript. J.F.S., A.A.N. and M.J.W. undertook the SIMS analysis. D.M.M. and J.F.P.-F. assisted with the FTIR data collection and interpretation. R.T. assisted with NanoSIMS data collection. V.V. assisted with the CL data acquisition. D.A.K. supported the regolith breccia research. All authors have read and have contributed to the final manuscript. Competing interests. We declare we have no competing interests. Funding. This research was facilitated by STFC (PhD studentship to Dayl Martin, and grant nos. ST/M001253/1, ST/ P005225/1 and ST/L002957/1) and the Royal Society (grant no. RS/UF140190) funding. K.H.J. acknowledges NASA Lunar Science Institute contract NNA09DB33A to D.A.K., which supported the JSC EMP analyses and thin section mapping. This is LPI Contribution number 2366. A.A.N. and M.J.W. were co-PI’s on the Knut and Alice Wallenberg Foundation grant no. 2012.0097 and Swedish Research Council grant no. 2012–04370, and the NordSIMS laboratory was funded under Swedish Research Council grant no. 2014–06375; this is NordSIMS contribution number 640. J.F.S. acknowledges funding from the European Commission Horizon 2020 Research and Innovation programme (Marie Skłodowska-Curie Actions Fellowship grant no. 794287). At The University of Manchester, the NanoSIMS was funded by UK Research Partnership Investment Funding (UKRPIF) Manchester RPIF Round 2. Acknowledgements. K.H.J. would like to thank the LPI library staff for digitizing the Warner et al. Apollo 16 technical report, and George Rossman at the Caltech Mineral Spectroscopy Server and Ming Zhang for their help locating zircon FTIR data. Also thanks to NASA JSC ARES staff for Roger Harrington for help with the thin section. We also thank Dr Marc Norman and two anonymous reviewers for their helpful comments on the manuscript.

FundersFunder number
UK Research Partnership Investment Funding
National Aeronautics and Space AdministrationNNA09DB33A
Horizon 2020 Framework Programme
H2020 Marie Skłodowska-Curie Actions794287
Science and Technology Facilities CouncilST/L002957/1, ST/M001253/1, ST/ P005225/1
Royal SocietyRS/UF140190
University of Manchester
Knut och Alice Wallenbergs Stiftelse2012.0097
Vetenskapsrådet2014–06375, 2012–04370

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