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Petrology and mineralogy of an igneous clast in the Northwest Africa 1685 (LL4) chondrite: Comparison with alkali‐rich igneous clasts in LL‐chondritic breccias
Author(s) -
Niihara Takafumi,
Yokoyama Tatsunori,
Arai Tomoko,
Misawa Keiji
Publication year - 2021
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.13719
Subject(s) - breccia , geology , geochemistry , igneous rock , chondrite , clastic rock , olivine , parent body , meteorite , petrology , mineralogy , sedimentary rock , astrobiology , physics
We have conducted petrological and mineralogical studies on an igneous clast in the Northwest Africa (NWA) 1685 (LL4) chondrite. This meteorite was described in the Meteoritical Bulletin as containing clasts similar to alkali‐rich clasts in LL chondritic breccias Yamato (Y)‐74442 (LL4), Bhola (LL3‐6), and Krähenberg (LL5). We carefully compared the textures, as well as mineral and matrix compositions, of the NWA 1685 clast with those of the previously described alkali‐rich clasts in the LL chondritic breccias. Olivine grains are embedded in glassy matrix and have no chemical zoning. Shock melt veins and fractures were observed only in olivine grains and did not continue into matrix. Potassium abundance of matrix glasses of the NWA 1685 clast is lower than those of alkali‐rich igneous clasts in Y‐74442, Bhola, and Krähenberg, indicating that the igneous clasts in NWA 1685 are different from the alkali‐rich clasts previously reported in the LL chondritic breccias. The NWA 1685 clast might have formed during an impact melting and quenching event on the LL‐chondrite parent body, and then been incorporated into a breccia.