DOI: 10.1016/j.epsl.2020.116497
论文题名: Evidence for early asteroidal collisions prior to 4.15 Ga from basaltic eucrite phosphate U–Pb chronology
作者: Koike M. ; Sano Y. ; Takahata N. ; Iizuka T. ; Ono H. ; Mikouchi T.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 549 语种: 英语
中文关键词: early collisional history of asteroids
; eucrites
; NanoSIMS
; U-Pb chronology of phosphates
; Vesta
英文关键词: Apatite
; Asteroids
; Basalt
; Geochronology
; Industrial heating
; Meteor impacts
; Meteorites
; Radiometry
; System stability
; Collisional process
; Different stages
; Dynamical calculations
; High temperature
; Late heavy bombardment
; Metamorphic events
; Radiometric chronology
; Terrestrial planets
; Gallium compounds
; apatite
; asteroid
; basalt
; data set
; eucrite
; geochronology
; meteorite
; phosphate
; uranium-lead dating
英文摘要: The late heavy bombardment (LHB) hypothesis, wherein the terrestrial planets are thought to have suffered intense collisions ca. 3.9 billion years ago, is under debate. Coupled with new dynamical calculations, re-examination of geochronological data seem to support an earlier solar system instability and a smooth monotonic decline in impacts, as opposed to a “cataclysm.” To better understand this collisional history, records from the asteroidal meteorites are required. Here, we report a uranium–lead (U–Pb) chronological dataset for eucrite meteorites thought to originate from the asteroid 4 Vesta; this dataset indicates to a continuous history of collisions prior to 4.15 Ga. Our 207Pb⁎/206Pb⁎ model ages of apatite [Ca5(PO4)3(F,Cl,OH)] and merrillite [Ca9NaMg(PO4)7] from three brecciated basaltic eucrites—Juvinas (4150.3 ± 11.6 million years ago (Ma); merrillite only), Camel Donga (disturbed around 4570–4370 Ma), and Stannern (4143.0 ± 12.5 Ma)—record multiple thermal metamorphic events during the period of ∼4.4–4.15 Ga. We interpret this to mean that Vesta or the vestoid cluster underwent multiple impacts and moderate high-temperature reheating during this time. The ages of ∼4.4–4.15 Ga are distinctly younger than the initial magmatic process on Vesta (>4.5 Ga) but are significantly older than a later “impact peak” based on some interpretations of 40Ar–39Ar chronologies (∼3.9–3.5 Ga). The intense collisions prior to 4.15 Ga on Vesta are at odds with the conventional LHB hypothesis but not inconsistent with the much earlier bombardment and monotonic decline scenario. Different radiometric chronologies of the asteroid likely represent the different stages of a continual collisional process. Conversely, the model 207Pb⁎/206Pb⁎ ages of apatite in the unbrecciated basaltic eucrite, Agoult, returned an age of 4524.8 ± 9.6 Ma. This may represent slow cooling from an earlier global reheating of the crust on Vesta at 4.55 Ga, as documented by other radiometric chronologies. The apatite in Juvinas recorded a coincident timing of 4516.9 ± 10.4 Ma, which could be due to either slow crustal cooling or impact. © 2020 The Author(s) Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165083
Appears in Collections: 气候变化与战略
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作者单位: Earth and Planetary Systems Science Program, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima-shi, Hiroshima, 739-8526, Japan; Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba 277-8564, Japan; Institute of Surface-Earth System Science, Tianjin University, Nankai District, Tianjin, 300072, China; Department of Earth and Planetary Science, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan; The University Museum, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
Recommended Citation:
Koike M.,Sano Y.,Takahata N.,et al. Evidence for early asteroidal collisions prior to 4.15 Ga from basaltic eucrite phosphate U–Pb chronology[J]. Earth and Planetary Science Letters,2020-01-01,549