NWA 10214—An LL3 chondrite breccia with an assortment of metamorphosed, shocked, and unique chondrite clasts

Abstract

NWA 10214 is an LL3‐6 breccia containing ~8 vol% clasts including LL5, LL6, 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, CAIs, and AOIs; the clast's matrix composition is close to that in CV3 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 CAIs. A chunk of this chondrite was ejected from its parent asteroid and later impacted the LL body at low relative velocity.

Geochemical and oxygen isotope perspective of a new R chondrite Dhofar 1671: Affinity with ordinary chondrites

“…), NWA 10214 (LL3; Rubin et al. ), and RCs, for example, POP chondrules in PCA91241 (R3.8–6; Greenwood et al. ) and Dhofar 1671 (R3.6; this study), supports that the source of the oxidation and 17 O‐enrichment could be the matrix, which may have been enriched in 17 O‐rich water.…”

Young asteroid mixing revealed in ordinary chondrites: The case of NWA 5764, a polymict LL breccia with L clasts

“…Also, an unmelted clast of ungrouped ordinary chondritic material has been described in the NWA 10214 LL3 chondrite (Rubin et al. ). NWA 5764, the object of study in this article, is the next one of these rare yet informative meteorites.…”

IIE irons: Origin, relationship to ordinary chondrites, and evidence for siderophile‐element fractionations caused by chondrule formation

“…In addition to the IIE chondritic inclusions, there are many reduced OC-like materials probably derived from several different parent bodies. Such samples include: a reduced OC-like clast from the NWA 10214 LL3-6 breccia (Rubin et al 2017); El M edano 301 (Pourkhorsandi et al 2017); Wray (a), Cerro los Calvos, Willaroy, Moorabie, and Suwahib (Buwah; Whitlock et al 1991;Wasson et al 1993;McCoy et al 1994); Y-982717 (Yamaguchi et al 2015); and Burnwell, EET 96031, and LAP 04575 (Russell et al 1998;Troiano et al 2011). Two modes of origin have been proposed for these samples-reduction during thermal metamorphism of normal OC in the presence of a reducing agent (Wasson et al 1993) and derivation from one or more distinct, more reduced parent bodies (e.g., McCoy et al 1994).…”

“…Minorto-accessory phases include pigeonite, phosphate, aenigmatite, oxide (ilmenite, rutile, armalcolite), pentlandite, and sodalite. Rubin et al (2017) pointed out that many fractionated IIE silicate inclusions have bulk compositions similar to those of melt pocket glasses in OC (Dodd and Jarosewich 1982). These melt pockets were most likely produced by preferential impact melting of chondritic minerals with low impedances to shock compression.…”