From whom Bells tolls: Reclassifying Bells among <scp>CR</scp> chondrites and implications for the formation conditions of <scp>CR</scp> parent bodies

Marrocchi, Yves; Jacquet, Emmanuel; Neukampf, Julia; Villeneuve, Johan; Zolensky, M. E.

doi:10.1111/maps.13947

Cited by 6 publications

(1 citation statement)

References 84 publications

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“…Matrix magnetites in some CMs have similar morphologies to those in CI and CR (e.g., Hyman et al., 1985). Magnetite is especially abundant in Bells, which is similar to CM2 but recently reclassified to CR2 (Marrocchi et al., 2023). Magnetite in unequilibrated CK and CV chondrites occurs as spheres within chondrules (e.g., Choi et al., 1997; Dunn et al., 2016), presumably replacing the metal blebs that are characteristic of many chondrules.…”

Section: Discussionmentioning

confidence: 99%

Nanophase magnetite in matrix of anomalous EL3 chondrite Northwest Africa (NWA) 8785

Weisberg,

Zolensky,

Kimura

et al. 2023

Meteorit & Planetary Scien

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NWA 8785 is a remarkable EL3 chondrite with a high abundance (~34 vol%) of an Fe‐rich matrix. This is the highest matrix abundance known among enstatite chondrites (ECs) and more similar to the matrix abundances in some carbonaceous and Rumuruti chondrites. X‐ray diffraction and TEM data indicate that the fine‐grained portion of the NWA 8785 matrix consists of nanoscale magnetite mixed with a noncrystalline silicate material and submicron‐sized enstatite and plagioclase grains. This is the first report of magnetite nanoparticles in an EL3. The Si content of the metal (0.7 wt%), presence of ferroan alabandite, and its O isotopic composition indicate NWA 8785 is EL3‐related. Having more abundant matrix than in other ECs, and that the matrix is rich in magnetite nanoparticles, which are not present in any other EC, suggest classification as an EL3 anomalous. Although we cannot completely exclude any of the mechanisms or environments for formation of the magnetite, we find a secondary origin to be the most compelling. We suggest that the magnetite formed due to hydrothermal activity in the meteorite parent body. Although ECs are relatively dry and likely formed within the nebular snow line, ices may have drifted inward from just beyond the snow line to the region where the EL chondrites were accreting, or more likely the snow line migrated inward during the early evolution of the solar system. This may have resulted in the condensation of ices and provided an ice‐rich region for accretion of the EL3 parent body. Thus, the EL3 parent body may have had hydrothermal activity and if Earth formed near the EC accretion zone, similar bodies may have contributed to the Earth's water supply. NWA 8785 greatly extends the range of known characteristics of ECs and EC parent body processes.

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Section: Discussionmentioning

confidence: 99%

Nanophase magnetite in matrix of anomalous EL3 chondrite Northwest Africa (NWA) 8785

Weisberg,

Zolensky,

Kimura

et al. 2023

Meteorit & Planetary Scien

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Chondrule Properties and Formation Conditions

Marrocchi,

Jones,

Russell

et al. 2024

Space Sci Rev

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Chondrules are iconic sub-millimeter spheroids representing the most abundant high-temperature dust formed during the evolution of the circumsolar disk. Chondrules have been the subject of a great deal of research, but no consensus has yet emerged as to their formation conditions. In particular, the question of whether chondrules are of nebular or planetary origin remains largely debated. Building upon decades of chondrule investigation and recent headways in combining petrographic observations and O−Ti−Cr isotopic compositions, we here propose a comprehensive vision of chondrule formation. This holistic approach points toward a nebular origin of both NC and CC chondrules, with repetitive high-temperature recycling processes controlling the petrographic and isotopic diversities shown by chondrules. Chondrule precursors correspond to mixing between (i) early-formed refractory inclusions ± NC-like dust and (ii) previous generation of chondrules ± CI-like material. Chondrule formation took place under open conditions with gas-melt interactions with multi-species gas (H2O, Mg, SiO) playing a key role for establishing their characteristics. Petrographic and isotopic systematics do not support disk-wide transport of chondrules but point toward local formation of chondrules within their respective accretion reservoirs. Altogether, this shows that several generations of genetically-related chondrules (i.e., deriving from each other) co-exist in chondrites. In addition to supporting the nebular brand of chondrule-forming scenarios, this argues for repetitive and extremely localized heating events for producing chondrules.

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Hydrogen isotopic evidence for nebular pre-hydration and the limited role of parent-body processes in CM chondrites

Marrocchi

Rigaudier

Piralla

et al. 2023

Earth and Planetary Science Letters

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From whom Bells tolls: Reclassifying Bells among CR chondrites and implications for the formation conditions of CR parent bodies

Cited by 6 publications

References 84 publications

Nanophase magnetite in matrix of anomalous EL3 chondrite Northwest Africa (NWA) 8785

Nanophase magnetite in matrix of anomalous EL3 chondrite Northwest Africa (NWA) 8785

Chondrule Properties and Formation Conditions

Hydrogen isotopic evidence for nebular pre-hydration and the limited role of parent-body processes in CM chondrites

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