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

Gattacceca, J.; Krzesińska, Agata M.; Marrocchi, Yves; Meier, M. M. M.; Bourot-Denise, M.; Lenssen, Rob

doi:10.1111/maps.12942

Cited by 9 publications

(7 citation statements)

References 51 publications

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“…Extraction of UH154-11 requires subsequent kilometer-deep excavation of the CV planetesimal crust by a large impact (45), which could have contributed to the compaction of the rest of the CV chondrite parent-body (46,47). Finally, trapping at the surface of the CR parent-body of a CVderived clast confirms that clasts in chondrites could originate from different parent-bodies (48) and implies that CV and CR planetesimals probably formed in the same region of the protoplanetary disk, rather than being dynamically isolated from each other (49).…”

Section: Significancementioning

confidence: 88%

Alkali magmatism on a carbonaceous chondrite planetesimal

Adnot

Aléon-Toppani

Platevoët

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Recent isotopic and paleomagnetic data point to a possible connection between carbonaceous chondrites and differentiated planetary materials, suggesting the existence, perhaps ephemeral, of transitional objects with a layered structure whereby a metal-rich core is enclosed by a silicate mantle, which is itself overlain by a crust containing an outermost layer of primitive solar nebula materials. This idea has not received broad support, mostly because of a lack of samples in the meteoritic record that document incipient melting at the onset of planetary differentiation. Here, we report the discovery and the petrologic–isotopic characterization of UH154-11, a ferroan trachybasalt fragment enclosed in a Renazzo-type carbonaceous chondrite (CR). Its chemical and oxygen isotopic compositions are consistent with very-low-degree partial melting of a Vigarano-type carbonaceous chondrite (CV) from the oxidized subgroup at a depth where fluid-assisted metamorphism enhanced the Na content. Its microdoleritic texture indicates crystallization at an increasing cooling rate, such as would occur during magma ascent through a chondritic crust. This represents direct evidence of magmatic activity in a carbonaceous asteroid on the verge of differentiating and demonstrates that some primitive outer Solar System objects related to icy asteroids and comets underwent a phase of magmatic activity early in the Solar System. With its peculiar petrology, UH154-11 can be considered the long-sought first melt produced during partial differentiation of a carbonaceous chondritic planetary body, bridging a previously persistent gap in differentiation processes from icy cometary bodies to fully melted iron meteorites with isotopic affinities to carbonaceous chondrites.

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Section: Significancementioning

confidence: 88%

Alkali magmatism on a carbonaceous chondrite planetesimal

Adnot

Aléon-Toppani

Platevoët

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…This is attested by the ubiquitous occurrence of brecciated textures in meteorites, with~30% of ordinary chondrites (OCs) and almost all CM carbonaceous chondrites showing brecciation features (Fig. 1A) (Bischoff et al 2006;Gattacceca et al 2017;Lentfort et al 2021;Suttle et al 2021). Such characteristics are fundamental because (1) OCs are by far the most common meteorites falling on Earth (~80%) and (2) CMs represent 25% of all carbonaceous chondrite falls (Gounelle et al 2005).…”

Section: Meteoritic Evidence Of Widespread Collision Processes In the Asteroid Beltmentioning

confidence: 98%

“…Genomict breccias define meteorites containing fragments of the same compositional group, but with different metamorphic or hydrothermal alteration histories (Fig. 2) (Gattacceca et al 2017;St€ offler et al 2018;Vacher et al 2018;Verdier-Paoletti et al 2019); these textures reflect large-scale brecciation processes occurring within a given parent body. In contrast, polymict breccias define meteorites composed of fragments originating from different parent bodies (Fig.…”

Section: Meteoritic Evidence Of Widespread Collision Processes In the Asteroid Beltmentioning

confidence: 99%

The astrophysical context of collision processes in meteorites

Marrocchi

Delbò

Gounelle

2021

Meteorit & Planetary Scien

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Chondrites are leftover solids from the early evolution of the solar protoplanetary disk that never experienced melting since their formation. They comprise unequilibrated assemblages of low-and high-temperature components, including volatile-rich, fine-grained matrices, Fe-Ni metal, sulfides, refractory inclusions, and chondrules. Consequently, chondrites are commonly described as pristine, primitive, or primordial rocks of the solar system. However, impact-generated secondary features are abundant in chondrites, suggesting that collisions among early-formed planetesimals and their fragmentation and reassembly have been effective throughout the evolution of the solar system. In this report, we review evidence of the major role of impacts in generating the current mineralogical and petrographic characteristics of chondrites. We provide perspective to these meteoritic features by discussing recent analyses of large-scale structures of the main asteroid belt and remote-sensing observations of asteroids. Observations at various spatial scales all attest that the "primitive" materials formed during the evolution of the solar system have largely been reprocessed, confirming previous studies that primitivity is relative, not absolute. This implies that (1) chondrites (and some differentiated meteorites) should systematically be envisioned as reprocessed and heterogeneous materials and (2) brecciated meteorites should be considered the norm and unbrecciated meteorites the exception.

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“…Meibom and Clark (1999) and Gattacceca et al (2017) note that unmelted macroscopic xenoliths of OCs of a type different from that of their host are rare in OCs. Binns (1967c) surveyed 361 OCs (at least 105 of which were brecciated) and found none containing unmelted xenoliths.…”

Section: Xenoliths Of Other Chondrite Types In Ordinary Chondritesmentioning

confidence: 99%

Xenoliths in ordinary chondrites and ureilites: Implications for early solar system dynamics

Goodrich

Kring

Greenwood

2021

Meteorit & Planetary Scien

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Foreign clasts (xenoliths) in meteoritic breccias are a serendipitous source of information about the impact environment in which their hosts formed, including impactor flux and cosmochemical types. These parameters may be related to timing and/or heliocentric distance of xenolith origin and implantation, and thus can be used to test or inform models of early solar system dynamics. We use xenoliths in ordinary chondrites (OCs) and ureilites to do this. We first conducted a petrologic and oxygen isotope study of a new, cm‐sized igneous‐textured clast in L3.7 Northwest Africa (NWA) 092, which highlighted some of the difficulties of identifying xenoliths in meteorites. Results indicate that this clast is not a xenolith but an impact melt of non‐local OC material. We add this result to a literature survey of more than 3000 OCs and find that the fraction of OCs that contain xenoliths is <<1%, and, even in these, the abundance and the diversity of xenoliths are very low. This contrasts markedly with the ureilites, ˜5% of which contain ˜1–10 vol% xenoliths from every major meteorite class, including multiple groups and petrologic types. To investigate reasons for this difference, we compare the histories of OC and ureilite parent bodies. The OC and ureilitic parent bodies accreted in the inner solar system within ˜1 AU of one another. The OC bodies accreted ˜2–3 Myr after calcium‐aluminum‐rich inclusion (CAI) formation and were heated slowly, experiencing thermal metamorphism over ˜50–60 Myr. The ureilite parent body (UPB) accreted <1 Myr after CAIs and was heated rapidly, experiencing partial melting over ˜4 Myr. Both OC parent bodies and the UPB were catastrophically disrupted and reassembled into rubble piles. For ureilites, this occurred ˜5.0–5.4 Ma after CAIs, while for OCs, it did not occur until 50–60 Myr after CAIs. Xenoliths in OC and ureilitic breccias were acquired as fragments of impactors on the rubble piles. The presence in polymict ureilites of xenoliths of all OC groups (H, L, LL) and petrologic types (3–6), and the intimate scale on which these and myriad other xenolith types are mixed, indicate that most xenoliths were acquired within a short time period around ˜50–60 Myr after CAIs when OC (likely also Rumuruti chondrite and enstatite chondrite) parent bodies were disrupted. This timing is consistent with the early instability dynamical model for a period of excitation in the asteroid belt. Outer solar system (CC) xenoliths were also acquired during this period, but were derived indirectly from C‐type bodies that had already been emplaced in orbits in the asteroid belt. The large discrepancy in xenolith abundance between ureilites and OC may be due to different physical properties of their regoliths at 50–60 Myr after CAIs. CC‐like xenoliths in OC may represent a different, more recently acquired, population than those in polymict ureilites.

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

Cited by 9 publications

References 51 publications

Alkali magmatism on a carbonaceous chondrite planetesimal

Alkali magmatism on a carbonaceous chondrite planetesimal

The astrophysical context of collision processes in meteorites

Xenoliths in ordinary chondrites and ureilites: Implications for early solar system dynamics

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