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Cl-bearing fluorcalciobritholite in high-Ti basalts from Apollo 11 and 17; implications for volatile histories of late-stage lunar magmas

James P. Greenwood, Kenichi Abe and Benjamin McKeeby
Cl-bearing fluorcalciobritholite in high-Ti basalts from Apollo 11 and 17; implications for volatile histories of late-stage lunar magmas
American Mineralogist (February 2020) 105 (2): 255-261

Abstract

We report the occurrence of a previously unidentified mineral in lunar samples: a Cl-,F-,REE-rich silico-phosphate identified as Cl-bearing fluorcalciobritholite. This mineral is found in late-stage crystallization assemblages of slowly cooled high-Ti basalts 10044, 10047, 75035, and 75055. It occurs as rims on fluorapatite or as a solid-solution between fluorapatite and Cl-fluorcalciobritholite. The Cl-fluorcalciobritholite appears to be nominally anhydrous. The Cl and Fe (super 2+) of the lunar Cl fluorcalciobritholite distinguishes it from its terrestrial analog. The textures and chemistry of the Cl fluorcalciobritholite argue for growth during the last stages of igneous crystallization, rather than by later alteration/replacement by Cl-, REE-bearing metasomatic agents in the lunar crust. The igneous growth of this Cl- and F-bearing and OH-poor mineral after apatite in the samples we have studied suggests that the Lunar Apatite Paradox model (Boyce et al. 2014) may be inapplicable for high-Ti lunar magmas. This new volatile-bearing mineral has important potential as a geochemical tool for understanding Cl isotopes and REE chemistry of lunar samples.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 105
Serial Issue: 2
Title: Cl-bearing fluorcalciobritholite in high-Ti basalts from Apollo 11 and 17; implications for volatile histories of late-stage lunar magmas
Affiliation: Wesleyan University, Department of Earth and Environmental Sciences, Middletown, CT, United States
Pages: 255-261
Published: 202002
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 33
Accession Number: 2020-048468
Categories: Mineralogy of silicatesExtraterrestrial geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 202014
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