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Primary feldspar in the Semarkona LL 3.00 chondrite: Constraints on chondrule formation and secondary alteration
Author(s) -
Lewis Jonathan A.,
Jones Rhian H.
Publication year - 2019
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.13194
Subject(s) - chondrule , plagioclase , chondrite , feldspar , geology , geochemistry , mineralogy , meteorite , astrobiology , quartz , paleontology , physics
Feldspar in ordinary chondrites ( OC s) 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 OC s 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 ( LL 3.00) and observed feldspar in 18% of chondrules. The feldspar is plagioclase covering a wide range of compositions (An 2 –An 99 ) with little K‐feldspar component (