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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2018: 2.631

CiteScore 2018: 2.55

SCImago Journal Rank (SJR) 2018: 1.355
Source Normalized Impact per Paper (SNIP) 2018: 1.103

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1945-3027
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Volume 98, Issue 10

Issues

Petrology and geochemistry of lunar granite 12032,366-19 and implications for lunar granite petrogenesis

Stephen M. Seddio
  • Corresponding author
  • Department of Earth and Planetary Sciences and the McDonnell Center for Space Sciences, Washington University, St. Louis, Missouri 63130, U.S.A.
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/ Bradley L. Jolliff
  • Department of Earth and Planetary Sciences and the McDonnell Center for Space Sciences, Washington University, St. Louis, Missouri 63130, U.S.A.
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/ Randy L. Korotev
  • Department of Earth and Planetary Sciences and the McDonnell Center for Space Sciences, Washington University, St. Louis, Missouri 63130, U.S.A.
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/ Ryan A. Zeigler
  • Astromaterials and Exploration Science Directorate, NASA, Johnson Space Center, mail code KT, 2101 NASA Pkwy, Houston, Texas 77058, U.S.A.
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Published Online: 2015-03-07 | DOI: https://doi.org/10.2138/am.2013.4330

Abstract

Apollo 12 sample 12032,366-19 is a 21.3 mg granite fragment that is distinct from any other lunar granite or felsite. It is composed of barian K-feldspar, quartz, sodic plagioclase, hedenbergite, fayalite, and ilmenite, with trace amounts of zirconolite, baddeleyite, apatite, and merrillite. The texture of 12032,366-19 is largely a micrographic intergrowth predominantly of K-feldspar and quartz and, to a lesser extent, plagioclase and quartz. Hedenbergite, fayalite, and ilmenite are present in minor but significant quantities-6.0, 3.1, and 1.7 wt%, respectively-and are scattered throughout the feldsparquartz intergrowths. Trace amounts of Zr-bearing phases are found including zirconolite (0.6 wt%) and baddeleyite (0.04 wt%). Incompatible trace-element concentrations are high in 12032,366-19, particularly the high-field-strength elements, e.g., Zr, Sm, and Th (1500, 25, and 61 μg/g, respectively). The chondrite-normalized, rare-earth-element concentrations form a “V-pattern” that is characteristic of other lunar granitic material. By modeling 12032,366-19 as a derivative from a KREEP-like parent melt, the composition and mineral assemblage can be obtained by extended fractional crystallization combined with separation of the low-density minerals plus trapped melt components prior to final solidification. However, this model cannot quantitatively account for the relatively sodic composition of the plagioclase (An34-50) and requires that the starting melt has Na2O of 1.2-1.4 wt%, which is higher than most KREEP compositions. Formation of this assemblage by silicate-liquid immiscibility is neither required nor indicated by petrogenetic modeling.

Keywords : Granite; Moon; zirconolite; apatite; felsite; Apollo 12

About the article

Received: 2012-08-24

Accepted: 2013-05-05

Published Online: 2015-03-07

Published in Print: 2013-10-01


Citation Information: American Mineralogist, Volume 98, Issue 10, Pages 1697–1713, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am.2013.4330.

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© 2015 by Walter de Gruyter Berlin/Boston.

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