Evidence for a Stratified Upper Mantle Preserved within the South Pole – Aitken Basin

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dc.contributor.authorMoriarty III, D. P.
dc.contributor.authorWatkins, R. N.
dc.contributor.authorValencia, S. N.
dc.contributor.authorKendall, J. D.
dc.contributor.authorEvans, A. J.
dc.contributor.authorDygert, N.
dc.contributor.authorPetro, N. E .
dc.date.accessioned2021-01-20T21:46:45Z
dc.date.available2021-01-20T21:46:45Z
dc.date.issued2020-12-18
dc.description.abstractThe evolution and compositional structure of the lunar mantle has been extensively modeled but insufficiently constrained by observations. Here, we identify and characterize mantle materials exposed by the Moon's largest impact basin to better understand the composition, stratigraphy, and evolution of the upper mantle. The vast South Pole‐Aitken Basin (SPA) exhibits a broad, crescent‐shaped thorium and potassium distribution. These incompatible elements are predicted to be concentrated in the dregs of the lunar magma ocean during end‐stage crystallization. Through consideration of basin formation models convolved with subsequent geologic evolution, we demonstrate that the distribution and implied stratigraphy of Th‐ and K‐bearing materials across SPA are consistent with an upper mantle ejecta origin. The most pristine exposures of these materials are confined to northwest SPA and also exhibit elevated Ti and Fe (relative to the farside highlands) in association with a gabbronoritic mineralogy. This is consistent with late‐stage magma ocean assemblages predicted by petrologic models. In contrast, SPA impact melt derived from greater depths is associated with a low‐Ca pyroxene‐dominated assemblage. Together, these compositional patterns are evidence for a stratified ancient upper mantle. Importantly, the incompatible‐element‐enriched, ilmenite‐bearing ferroan gabbronoritic cumulates evidently had not participated in gravitational overturn at the time of SPA formation. Contrary to recent hypotheses invoking nearside sequestration of incompatible elements to explain hemispherical differences in crustal building and volcanic resurfacing, it follows that incompatible elements were globally distributed in the magma ocean at the time of SPA formation.en_US
dc.description.sponsorshipSignificant portions of this work were conducted by the TREX team and supported by the National Aeronautics and Space Administration (NASA) through the Solar System Exploration Virtual Institute 2016 (SSERVI2016) Cooperative Agreement (NNH16ZDA001N).en_US
dc.description.urihttps://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JE006589en_US
dc.format.extent2 filesen_US
dc.genrejournal articles postprintsen_US
dc.identifierdoi:10.13016/m2yg5f-zb7n
dc.identifier.citationMoriarty III, D. P.; Watkins, R. N.; Valencia, S. N.; Kendall, J. D.; Evans, A. J.; Dygert, N.; Petro, N. E .; Evidence for a Stratified Upper Mantle Preserved within the South Pole – Aitken Basin; Journal of Geophysical Research: Planets (2020); https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JE006589en_US
dc.identifier.urihttps://doi.org/10.1029/2020JE006589
dc.identifier.urihttp://hdl.handle.net/11603/20573
dc.language.isoen_USen_US
dc.publisherAmerican Geophysical Unionen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Center for Space Sciences and Technology
dc.relation.ispartofUMBC Faculty Collection
dc.relation.ispartofUMBC Physics Department
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
dc.rightsPublic Domain Mark 1.0*
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law
dc.rights.urihttp://creativecommons.org/publicdomain/mark/1.0/*
dc.titleEvidence for a Stratified Upper Mantle Preserved within the South Pole – Aitken Basinen_US
dc.typeTexten_US

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