Zinc isotopic variations in ureilites

Brugier, Yann-Aurélien; Barrat, Jean‐Alix; Guéguen, Bleuenn; Agranier, Arnaud; Yamaguchi, A.; Bischoff, A.

doi:10.1016/j.gca.2018.12.009

Cited by 8 publications

(2 citation statements)

References 71 publications

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“…Ureilites are also primitive achondrites that are likely to represent samples from a planetary mantle that was catastrophically disrupted before it could fully differentiate 23 . They range in composition from dunite to peridotite (olivine Fo 74-97 ) 24 , but like brachinites and brachinite-like achondrites, they are not from a fully differentiated asteroid.…”

Section: Introductionmentioning

confidence: 99%

Olivine-rich achondrites from Vesta and the missing mantle problem

et al. 2021

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Mantles of rocky planets are dominantly composed of olivine and its high-pressure polymorphs, according to seismic data of Earth’s interior, the mineralogy of natural samples, and modelling results. The missing mantle problem represents the paucity of olivine-rich material among meteorite samples and remote observation of asteroids, given how common differentiated planetesimals were in the early Solar System. Here we report the discovery of new olivine-rich meteorites that have asteroidal origins and are related to V-type asteroids or vestoids. Northwest Africa 12217, 12319, and 12562 are dunites and lherzolite cumulates that have siderophile element abundances consistent with origins on highly differentiated asteroidal bodies that experienced core formation, and with trace element and oxygen and chromium isotopic compositions associated with the howardite-eucrite-diogenite meteorites. These meteorites represent a step towards the end of the shortage of olivine-rich material, allowing for full examination of differentiation processes acting on planetesimals in the earliest epoch of the Solar System.

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Section: Introductionmentioning

confidence: 99%

Olivine-rich achondrites from Vesta and the missing mantle problem

et al. 2021

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“…A catastrophic disruption induced by a giant impact is believed to have occurred on UPB, because the main group ureilites (plus Almahata Sitta) usually show petrologic evidence of extremely rapid cooling (approximately 1∼20°C hr −1 ), accompanied by a drop in pressure, through the range 1100∼650°C (Miyamoto et al 1985;Mittlefehldt et al 1998;Herrin et al 2010). This impact can effectively cause a thermal pause to reset the isotopic dating systems for the ureilites located at the surface or subsurface on UPB, which also cause the Zn evaporation (Moynier et al 2010;Brugier et al 2019). Moreover, the rapid melting and cooling can also cause the large ε 54 Cr variations between individual clasts of polymict ureilites (Van Kooten et al 2017), and maybe also the heterogeneous Δ 17 O in Almahata Sitta (Rumble et al 2010;Bischoff et al 2014).…”

Section: Upb Experienced An Impact Event 4∼5 Myr After Solar System Fmentioning

confidence: 99%

Chromium Isotopic Constraints on the Origin of the Ureilite Parent Body

Zhu

Moynier

Schiller

et al. 2020

ApJ

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We report on the mass-independent Cr isotope compositions of 11 main group ureilites and an ureilitic trachyandesite (ALM-A). The 54 Cr/ 52 Cr ratios for main group ureilites vary from −1.06±0.04 to −0.78±0.05 and averaged at −0.91±0.15 (2SD, N=18) including the data from literature. We argue that this variation reflects primitive mantle heterogeneities within the ureilite parent body (UPB). As such, this body did not experience a global-scale magma ocean, which is consistent with heterogeneous O isotope in ureilites. Furthermore, the ε 54 Cr values, Mn/Cr ratios, C isotope ratios, Mg#values, and Fe/Mn ratios in the olivine cores of ureilites are correlated with each other, which suggests the mixing of ureilite precursors from at least two reservoirs, rather than a smelting process or the oxidation from ice melting. All the ureilite samples (including the ALM-A) fall on a well-defined 53 Mn-53 Cr isochron corresponding to a 53 Mn/ 55 Mn ratio of (6.02 ± 1.59)×10 −6 , which translates to an age of 4566.7±1.5 Ma (within 2 Ma after calcium-aluminum-rich inclusions; CAIs) when anchored to the U-corrected Pb-Pb age for the D'Orbigny angrite. This old age indicates early partial melting on the UPB, consistent with the early accretion of the UPB (within 1 Ma after CAIs) predicted by thermal modeling. Furthermore, there is a 4∼5 Ma age difference between the external isochron in this study and internal isochron ages for the feldspathic clasts in polymict ureilites, which likely reflects an impact history during the early evolution of the UPB.

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