DOI: 10.1016/j.epsl.2020.116506
论文题名: Petrological evidence for the existence and disruption of a 500 km-sized differentiated planetesimal of enstatite-chondritic parentage
作者: Harries D. ; Bischoff A.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 548 语种: 英语
中文关键词: accretion
; differentiation
; enstatite achondrite
; petrology
; pyroxenes
; transmission electron microscopy
英文关键词: Cooling
; High resolution transmission electron microscopy
; Iron oxides
; Lithology
; Meteorites
; Silicate minerals
; Solar system
; Sulfur compounds
; High cooling rates
; Metal sulfides
; Orthoenstatite
; Parent bodies
; Protoenstatite
; Rapid cooling
; Re-distribution
; Terrestrial planets
; Gasoline
; achondrite
; enstatite chondrite
; lithology
; petrology
; planetesimal
; protolith
; silicate
; Sitta
英文摘要: Two samples of a unique achondritic lithology of the Almahata Sitta meteorite (MS-MU-019 and MS-MU-036) contain three coexisting pyroxene species: orthoenstatite, clinoenstatite and augite. The silicate assemblage appears to be the restite after extraction of melts of broadly basaltic and metal-sulfide composition from an enstatite chondrite protolith. Transmission electron microscopy (TEM) provides evidence that clinoenstatite within the lithology formed from earlier protoenstatite. The absence of pigeonite despite the successful nucleation of augite and the persistence of orthoenstatite during cooling suggests that the sub-solidus formation of the three coexisting pyroxenes occurred at a pressure of about 0.1 GPa. Rapid cooling at >1 K/h below 1260°C is documented by the cessation of augite equilibration, preservation of the 3-pyroxene assemblage and a low volume fraction of nanoscale orthoenstatite lamellae formed during the transformation of protoenstatite to clinoenstatite. The pressure implies a diameter of roughly 500 km of the differentiated parent body, putting petrological constraints on the size of planetesimals that may have contributed to the accretion of the terrestrial planets including Earth. The high cooling rate indicates a catastrophic disruption of this large planetesimal early in its history. The lithology studied here underlines that planetesimals which existed in the inner Solar System were more diverse than previously thought, and included potentially large differentiated bodies with very FeO-poor, enstatite-dominated mantles. Remains of these bodies are poorly represented in meteorite collections, which points to efficient accretion in the inner Solar System or to removal and little re-distribution of material into the present-day asteroid belt. © 2020 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165010
Appears in Collections: 气候变化与战略
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作者单位: Institute für Geowissenschaften, Friedrich-Schiller-Universität Jena, Carl-Zeiss-Promenade 10, Jena, 07745, Germany; Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, Münster, 48149, Germany
Recommended Citation:
Harries D.,Bischoff A.. Petrological evidence for the existence and disruption of a 500 km-sized differentiated planetesimal of enstatite-chondritic parentage[J]. Earth and Planetary Science Letters,2020-01-01,548