DOI: 10.1016/j.epsl.2018.02.020
Scopus记录号: 2-s2.0-85042583905
论文题名: Length-scales of chemical and isotopic heterogeneity in the mantle section of the Shetland Ophiolite Complex, Scotland
作者: O'Driscoll B. ; Walker R.J. ; Clay P.L. ; Day J.M.D. ; Ash R.D. ; Daly J.S.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 488 起始页码: 144
结束页码: 154
语种: 英语
英文关键词: highly siderophile elements
; mantle heterogeneity
; oceanic mantle
; Re–Os isotopes
; Shetland Ophiolite Complex
Scopus关键词: Iridium
; Lithology
; Osmium
; Structural geology
; Trace elements
; Highly siderophile elements
; Mantle heterogeneity
; oceanic mantle
; Ophiolite complex
; Os isotopes
; Isotopes
; heterogeneity
; isotopic composition
; mantle chemistry
; melt
; ophiolite
; osmium
; peridotite
; rhenium
; siderophile element
; Scotland
; United Kingdom
英文摘要: Kilometre to sub-metre scale heterogeneities have been inferred in the oceanic mantle based on sampling of both ophiolites and abyssal peridotites. The ∼492 Ma Shetland Ophiolite Complex (SOC) contains a well-preserved mantle section that is dominated by harzburgite (∼70 vol.%) previously reported to have variable major and trace element compositions, yet dominantly chondritic initial 187Os/188Os compositions. To assess the preservation of compositional heterogeneities at sub-metre length-scales in the oceanic mantle, a ∼45 m2 area of the SOC mantle section was mapped and sampled in detail. Harzburgites, dunites and a pyroxenite from this area were analysed for lithophile and highly-siderophile element (HSE) abundances, as well as for 187Os/188Os ratios. Lithophile element data for most rocks are characteristic of supra-subduction zone (SSZ) metasomatic processes. Two dunites have moderately fractionated HSE patterns and suprachondritic γOs(492 Ma) values (+5.1 and +7.5) that are also typical of ophiolitic dunites generated by SSZ melt–rock interactions. By contrast, six harzburgites and four dunites have approximately chondritic-relative abundances of Os, Ir and Ru, and γOs(492 Ma) values ranging only from −0.6 to +2.7; characteristics that imply no significant influence during SSZ processes. Two harzburgites are also characterised by significantly less radiogenic γOs(492 Ma) values (−3.5 and −4), and yield Mesoproterozoic time of Re depletion (TRD) model ages. The range of Os isotope compositions in the studied area is comparable to the range reported for a suite of samples representative of the entire SOC mantle section, and approaches the total isotopic variation of the oceanic mantle, as observed in abyssal peridotites. Mechanisms by which this heterogeneity can be formed and preserved involve inefficient and temporally distinct melt extraction events and strong localised channelling of these melts. © 2018 Elsevier B.V.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109983
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: School of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom; Department of Geology, University of Maryland, College Park, MD, United States; Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, United States; UCD School of Earth Sciences, UCD Earth Institute, University College Dublin, Dublin, Ireland; Irish Centre for Research in Applied Geosciences (iCRAG), Belfield, Dublin, Ireland
Recommended Citation:
O'Driscoll B.,Walker R.J.,Clay P.L.,et al. Length-scales of chemical and isotopic heterogeneity in the mantle section of the Shetland Ophiolite Complex, Scotland[J]. Earth and Planetary Science Letters,2018-01-01,488