Primary feldspar in the Semarkona LL3.00 chondrite: Constraints on chondrule formation and secondary alteration

Feldspar in ordinary chondrites (OCs) is often associated with thermal metamorphism, as a secondary mineral that forms from the crystallization of matrix and chondrule mesostasis. However, studies of feldspar in equilibrated OCs show that there is a range of plagioclase compositions within chondrule...

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Bibliographic Details
Published in:Meteoritics & planetary science 2019-01, Vol.54 (1), p.72-89
Main Authors: Lewis, Jonathan A., Jones, Rhian H.
Format: Article
Language:English
Subjects:
Aluminum
Chondrites
Chondrule
Composition
Crystallization
Glass
Heterogeneity
Metamorphism
Metamorphism (geology)
Morphology
Plagioclase
Porosity
Solidus
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Summary:Feldspar in ordinary chondrites (OCs) is often associated with thermal metamorphism, as a secondary mineral that forms from the crystallization of matrix and chondrule mesostasis. However, studies of feldspar in equilibrated OCs show that there is a range of plagioclase compositions within chondrules, some of which may be primary products of chondrule crystallization. It is important to recognize primary feldspar within chondrules because it can be used to help understand the secondary effects of thermal metamorphism and aqueous alteration. The presence of primary feldspar also provides important petrologic constraints on chondrule formation time scales. We undertook a careful study of Semarkona (LL3.00) and observed feldspar in 18% of chondrules. The feldspar is plagioclase covering a wide range of compositions (An2–An99) with little K‐feldspar component (
ISSN:1086-9379
1945-5100
DOI:10.1111/maps.13194