DOI: 10.1016/j.epsl.2017.10.029
Scopus记录号: 2-s2.0-85033609107
论文题名: Evidence for accretion of fine-grained rims in a turbulent nebula for CM Murchison
作者: Hanna R.D. ; Ketcham R.A.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 481 起始页码: 201
结束页码: 211
语种: 英语
英文关键词: accretionary rims
; chondrules
; fine-grained rims
; nebular turbulence
; solar nebula
; X-ray CT
Scopus关键词: Computerized tomography
; Meteorites
; Surface roughness
; Turbulence
; Accretionary
; chondrules
; Fine grained
; Solar nebula
; X-ray CT
; Law enforcement
; algorithm
; chondrite
; chondrule
; deformation
; dust
; surface roughness
; tomography
; turbulence
英文摘要: We use X-ray computed tomography (XCT) to examine the 3D morphology and spatial relationship of fine-grained rims (FGRs) of Type I chondrules in the CM carbonaceous chondrite Murchison to investigate the formation setting (nebular vs. parent body) of the FGRs. We quantify the sizes, shapes, and orientations of the chondrules and FGRs and develop a new algorithm to examine the 3D variation of FGR thickness around each chondrule. We find that the average proportion of chondrule volume contained in the rim for Murchison chondrules is 35.9%. The FGR volume in relation to the interior chondrule radius is well described by a power law function as proposed for accretion of FGRs in a weakly turbulent nebula by Cuzzi (2004). The power law exponent indicates that the rimmed chondrules behaved as Stokes number Stη>1 nebular particles in Kolmogorov η scale turbulence. FGR composition as inferred from XCT number appears essentially uniform across interior chondrule types and compositions, making formation by chondrule alteration unlikely. We determine that the FGRs were compressed by the impact event(s) that deformed Murchison (Hanna et al., 2015), resulting in rims that are thicker in the plane of foliation but that still preserve their nebular morphological signature. Finally, we propose that the irregular shape of some chondrules in Murchison is a primary feature resulting from chondrule formation and that chondrules with a high degree of surface roughness accreted a relatively larger amount of nebular dust compared to smoother chondrules. © 2017 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/110170
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Jackson School of Geosciences, University of Texas, Austin, TX 78712, United States
Recommended Citation:
Hanna R.D.,Ketcham R.A.. Evidence for accretion of fine-grained rims in a turbulent nebula for CM Murchison[J]. Earth and Planetary Science Letters,2018-01-01,481