Xenon systematics of individual lunar zircons, a new window on the history of the lunar surface
| Autor: | Kevin D. McKeegan, C. A. Crow, Henner Busemann, Grenville Turner, Jamie Gilmour, Sarah Crowther |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Zircon
Xenon 010504 meteorology & atmospheric sciences Fission Rare-earth element Geochemistry chemistry.chemical_element Uranium 010502 geochemistry & geophysics Regolith 01 natural sciences Impact chemistry Geochemistry and Petrology Breccia Impact structure Lunar Geology 0105 earth and related environmental sciences |
| Zdroj: | Crow, C, Crowther, S, McKeegan, K, Turner, G, Busemann, H & Gilmour, J 2020, ' Xenon systematics of individual lunar zircons, a new window on the history of the lunar surface ', Geochimica et Cosmochimica Acta, vol. 286, pp. 103-118 . https://doi.org/10.1016/j.gca.2020.06.019 |
| ISSN: | 0016-7037 |
| DOI: | 10.1016/j.gca.2020.06.019 |
| Popis: | We demonstrate a new way of investigating the processing of the lunar surface (and other planetary regoliths) that combines XeS-XeN ages (based on uranium fission) in individual zircons with their xenon isotopic record of solar wind and cosmic ray exposure. We report the first xenon isotopic analyses of individual lunar zircons (from Apollo 14 soil and breccias samples). Parallel analyses of a suite of zircons from the Vredefort impact structure in South Africa revealed XeS-XeN ages that agree well with U-Pb systematics, suggesting that the diffusion kinetics of xenon and lead in zircon are similar in the pressure-temperature environment of sub-basin floors. In contrast, all Apollo 14 zircons examined exhibit XeS-XeN ages markedly younger than the associated U-Pb and 207Pb-206Pb ages, and soil zircons with 207Pb-206Pb ages greater than 3900 Ma produced an abundance of XeS-XeN ages 2400 Ma, suggesting that these samples may be useful for investigating ancient events and regolith processing at an earlier epoch. However, none of the zircons contain xenon from now-extinct 244Pu implying that either the samples have completely degassed since ∼3900 Ma or that the initial Pu/U ratio of the Moon is lower than that on Earth. We also describe a methodology for conducting component deconvolution that can be applied to multi-isotopes systems beyond xenon. We have also determined new xenon isotopic yields from rare earth element spallation in the lunar environment and high precision yields for neutron induced fission of 235U in geologic samples. |
| Databáze: | OpenAIRE |
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