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NWA 10214—An LL 3 chondrite breccia with an assortment of metamorphosed, shocked, and unique chondrite clasts
Author(s) -
Rubin Alan E.,
Breen John P.,
Isa Junko,
Tutorow Sean
Publication year - 2017
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.12797
Subject(s) - chondrule , chondrite , pyroxene , breccia , olivine , geology , geochemistry , enstatite , mafic , parent body , mineralogy , meteorite , physics , astrobiology
NWA 10214 is an LL 3‐6 breccia containing ~8 vol% clasts including LL 5, LL 6, and shocked‐darkened LL fragments as well as matrix‐rich Clast 6 (a new kind of chondrite). This clast is a dark‐colored, subrounded, 6.1 × 7.0 mm inclusion, consisting of 60 vol% fine‐grained matrix, 32 vol% coarse silicate grains, and 8 vol% coarse opaque grains. The large chondrules and chondrule fragments are mainly Type IB ; one small chondrule is Type IIA . Also present are one 450 × 600 μm spinel‐pyroxene‐olivine CAI and one 85 × 110 μm AOI . Clast 6 possesses a unique set of properties. (1) It resembles carbonaceous chondrites in having relatively abundant matrix, CAI s, and AOI s; the clast's matrix composition is close to that in CV 3 Vigarano. (2) It resembles type‐3 OC in its olivine and low‐Ca pyroxene compositional distributions, and in the Fe/Mn ratio of ferroan olivine grains. Its mean chondrule size is within 1σ of that of H chondrites. The O‐isotopic compositions of the chondrules are in the ordinary‐ and R‐chondrite ranges. (3) It resembles type‐3 enstatite chondrites in the minor element concentrations in low‐Ca pyroxene grains and in having a high low‐Ca pyroxene/olivine ratio in chondrules. Clast 6 is a new variety of type‐3 OC , somewhat more reduced than H chondrites or chondritic clasts in the Netschaevo IIE iron; the clast formed in a nebular region where aerodynamic radial drift processes deposited a high abundance of matrix material and CAI s. A chunk of this chondrite was ejected from its parent asteroid and later impacted the LL body at low relative velocity.