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An alternate hypothesis for the origin of Angra dos Reis - Porphyry, not cumulateThe Angra dos Reis achondrite is a unique meteorite of potentially great importance for understanding the origins of the solar system and of the terrestrial planets. It is proposed that the meteorite, which consists of megacrysts of Al-Ti augite (fassaite) in skeletal or cellular shapes, olivine, and possibly whitlockite in a fine-grained groundmass of the same materials plus spinel, is a porphyritic igneous rock modified by metamorphism. In this interpretation, the megacrysts represent cellular-textured phenocrysts, and the fine-grain groundmass represents crystallized or devitrified magma. Phase equilibria suggest that Angra dos Reis-like compositions could grow phenocrysts of fassaite pyroxene, olivine, and whitlockite. These same compositions could crystallize, without crystal sorting or accumulation, to an almost monomineralic fassaite pyroxenite.
Document ID
19890049152
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Treiman, A. H.
(Boston University MA, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1989
Subject Category
Lunar And Planetary Exploration
Meeting Information
Meeting: Lunar and Planetary Science Conference
Location: Houston, TX
Country: United States
Start Date: March 14, 1988
End Date: March 18, 1988
Accession Number
89A36523
Funding Number(s)
CONTRACT_GRANT: NAG9-168
Distribution Limits
Public
Copyright
Other

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