Mineralogy and petrogenesis of lunar magnesian granulitic meteorite Northwest Africa 5744

1Jeremy J. Kent,2Alan D. Brandon,3Katherine H. Joy,4Anne H. Peslier,2Thomas J. Lapen,5Anthony J. Irving,6Daniel M. Coleff
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12898]
1GeoControl Systems, Jacobs J.E.T.S. Contract, NASA-Johnson Space Center, Houston, Texas, USA
2University of Houston, Department of Earth and Atmospheric Sciences, Houston, Texas, USA
3School of Earth and Environmental Sciences, University of Manchester, Manchester, UK
4Jacobs, NASA-Johnson Space Center, Houston, Texas, USA
5University of Washington, Department of Earth and Space Sciences, Seattle, Washington, USA
6HX5, Jacobs J.E.T.S. Contract, NASA-Johnson Space Center, Houston, Texas, USA
Published by arrangement with john Wiley & Sons

Lunar meteorite Northwest Africa (NWA) 5744 is a granulitic breccia with an anorthositic troctolite composition that may represent a distinct crustal lithology not previously described. This meteorite is the namesake and first-discovered stone of its pairing group. Bulk rock major element abundances show the greatest affinity to Mg-suite rocks, yet trace element abundances are more consistent with those of ferroan anorthosites. The relatively low abundances of incompatible trace elements (including K, P, Th, U, and rare earth elements) in NWA 5744 could indicate derivation from a highlands crustal lithology or mixture of lithologies that are distinct from the Procellarum KREEP terrane on the lunar nearside. Impact-related thermal and shock metamorphism of NWA 5744 was intense enough to recrystallize mafic minerals in the matrix, but not intense enough to chemically equilibrate the constituent minerals. Thus, we infer that NWA 5744 was likely metamorphosed near the lunar surface, either as a lithic component within an impact melt sheet or from impact-induced shock.

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