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Brearleyite, Ca (sub 12) Al (sub 14) O (sub 32) Cl (sub 2) , a new alteration mineral from the NWA 1934 Meteorite

Chi Ma, Harold C. Connolly, John R. Beckett, Oliver Tschauner, George R. Rossman, Anthony R. Kampf, Thomas J. Zega, Stuart A. Sweeney Smith and Devin L. Schrader
Brearleyite, Ca (sub 12) Al (sub 14) O (sub 32) Cl (sub 2) , a new alteration mineral from the NWA 1934 Meteorite
American Mineralogist (August 2011) 96 (8-9): 1199-1206


Brearleyite (IMA 2010-062, Ca (sub 12) Al (sub 14) O (sub 32) Cl (sub 2) ) is a Cl-bearing mayenite, occurring as fine-grained aggregates coexisting with hercynite, gehlenite, and perovskite in a rare krotite (CaAl (sub 2) O (sub 4) ) dominant refractory inclusion from the Northwest Africa 1934 CV3 carbonaceous chondrite. The phase was characterized by SEM, TEM-SAED, micro-Raman, and EPMA. The mean chemical composition of the brearleyite is (wt%) Al (sub 2) O (sub 3) 48.48, CaO 45.73, Cl 5.12, FeO 0.80, Na (sub 2) O 0.12, TiO (sub 2) 0.03, -O 1.16, sum 99.12. The corresponding empirical formula calculated on the basis of 34 O+Cl atoms is (Ca (sub 11.91) Na (sub 0.06) ) (sub Sigma 11.97) (Al (sub 13.89) Fe (sub 0.16) Ti (sub 0.01) ) (sub Sigma 14.06) O (sub 31.89) Cl (sub 2.11) . The Raman spectrum of brealryeite indicates very close structural similarity to synthetic Ca (sub 12) Al (sub 14) O (sub 32) Cl (sub 2) . Rietveld refinement of an integrated TEM-SAED ring pattern from a FIB section quantifies this structural relationship and indicates that brearleyite is cubic, I43d; a=11.98(8) Aa, V=1719.1(2) Aa (super 3) , and Z=2. It has a framework structure in which AlO (sub 4) tetrahedra share corners to form eight-membered rings. Within this framework, the Cl atom is located at a special position (3/8,0,1/4) with 0.4(2) occupancy and Ca appears to be disordered on two partially occupied sites similar to synthetic Cl-mayenite. Brearleyite has a light olive color under diffuse reflected light and a calculated density of 2.797 g/cm (super 3) . Brearleyite is not only a new meteoritic Ca-,Al-phase, but also a new meteoritic Cl-rich phase. It likely formed by the reaction of krotite with Cl-bearing hot gases or fluids.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 96
Serial Issue: 8-9
Title: Brearleyite, Ca (sub 12) Al (sub 14) O (sub 32) Cl (sub 2) , a new alteration mineral from the NWA 1934 Meteorite
Affiliation: California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States
Pages: 1199-1206
Published: 201108
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 28
Accession Number: 2011-076461
Categories: Mineralogy of non-silicatesPetrology of meteorites and tektites
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
Secondary Affiliation: CUNY, Kingsborough Community College, USA, United StatesNatural History Museum of Los Angeles County, USA, United StatesNaval Research Laboratory, USA, United StatesAmerican Museum of Natural History, USA, United StatesUniversity of Arizona, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201142
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