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The case for the angrite parent body as the archetypical first-generation planetesimal: Large, reduced and Mg-enriched

Tissot, Francois und Collinet, Max und Namur, Olivier und Grove, Timothy (2022) The case for the angrite parent body as the archetypical first-generation planetesimal: Large, reduced and Mg-enriched. Geochimica et Cosmochimica Acta, 338 (1), Seiten 278-301. Elsevier. doi: 10.1016/j.gca.2022.09.031. ISSN 0016-7037.

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Offizielle URL: https://www.sciencedirect.com/science/article/abs/pii/S0016703722005178

Kurzfassung

Angrites are silica-undersaturated achondrites formed very early in the history of the Solar System, and the most volatile-depleted known meteorites. As such, the study of angrites can provide critical insights into the early stages of planetary formation, melting and differentiation. Yet, understanding the origins of angrites and the nature of their parent body has long been hindered by the initially small number of specimens available. Here, we leverage (i) the rapidly growing number of known angrites, and (ii) equilibrium crystallization experiments at various pressure, temperature and oxygen fugacity conditions (P-T-fO2), to revisit the petrogenesis of angrites and constrain key features of the angrite parent body (APB), such as its composition and size. We observe that quenched (i.e., volcanic) angrites define two compositional groups, which we show are readily related by fractional crystallization. This crystallization trend converges on an olivine-clinopyroxene-plagioclase (Ol + Cpx + Plag) multiple saturation boundary, whose composition is sampled by D’Orbigny, Sahara 99555 and NWA 1296. Using the observation that some quenched specimens represent primitive angritic melts, we derive a self-consistent bulk composition for the APB. We find that this composition matches the proposed Mg/Si ratio of 1.3 derived from the angrite δ30Si values, and yields a core size (18 ± 6 wt%) in agreement with the siderophile elements depletion in the APB mantle. Our results support a primary control of nebular fractionation (i.e., partial condensation) on the composition of the APB. To establish the liquid phase equilibria of angrites, a series of 1 atmosphere and high-pressure crystallization experiments (piston cylinder and internally heated pressure vessel) were performed on a synthetic powder of D’Orbigny. The results suggest that the APB was a large (possibly Moon-sized) body, formed from materials condensed at relatively high-temperature (∼1300–1400 K), and whose fO2 changed from mildly reducing (∼IW-1.5) to relatively oxidizing (∼IW+1 ± 1) in the ∼ 3 Myr between its core formation and the crystallization of D’Orbigny-like (Group 2) angrites. Based on its timing of accretion and differentiation, its composition, redox, and size, we argue that the APB represents the archetype of the first-generation of refractory-enriched planetesimals and embryos formed in the innermost part of the inner Solar System (<1 AU), and which accreted in the telluric planets.

elib-URL des Eintrags:https://elib.dlr.de/186761/
Dokumentart:Zeitschriftenbeitrag
Titel:The case for the angrite parent body as the archetypical first-generation planetesimal: Large, reduced and Mg-enriched
Autoren:
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iDORCID Put Code
Tissot, FrancoisCalifornia Institute of TechnologyNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Collinet, Maxmax.collinet (at) dlr.dehttps://orcid.org/0000-0002-8791-9751NICHT SPEZIFIZIERT
Namur, OlivierDepartment of Earth and Environmental Sciences, KU Leuven, 3001 Leuven, BelgiumNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Grove, TimothyDept. of Earth Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambrige, USANICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Datum:1 Dezember 2022
Erschienen in:Geochimica et Cosmochimica Acta
Referierte Publikation:Ja
Open Access:Ja
Gold Open Access:Nein
In SCOPUS:Ja
In ISI Web of Science:Ja
Band:338
DOI:10.1016/j.gca.2022.09.031
Seitenbereich:Seiten 278-301
Verlag:Elsevier
ISSN:0016-7037
Status:veröffentlicht
Stichwörter:planetary differentiation, accretion, achondrite
HGF - Forschungsbereich:Luftfahrt, Raumfahrt und Verkehr
HGF - Programm:Raumfahrt
HGF - Programmthema:Erforschung des Weltraums
DLR - Schwerpunkt:Raumfahrt
DLR - Forschungsgebiet:R EW - Erforschung des Weltraums
DLR - Teilgebiet (Projekt, Vorhaben):R - Exploration des Sonnensystems
Standort: Berlin-Adlershof
Institute & Einrichtungen:Institut für Planetenforschung > Planetenphysik
Hinterlegt von: Collinet, Max
Hinterlegt am:29 Nov 2022 09:39
Letzte Änderung:05 Mär 2024 08:31

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