DOI: 10.1038/ngeo2628
论文题名: Early Archaean tectonics and mantle redox recorded in Witwatersrand diamonds
作者: Smart K.A. ; Tappe S. ; Stern R.A. ; Webb S.J. ; Ashwal L.D.
刊名: Nature Geoscience
ISSN: 17520894
出版年: 2016
卷: 9, 期: 3 起始页码: 255
结束页码: 259
语种: 英语
Scopus关键词: carbon isotope
; crustal recycling
; diamond
; geochemical method
; Hadean
; isotopic analysis
; isotopic composition
; mantle process
; nitrogen
; oxidation
; plate tectonics
; reduction
; subduction
; subduction zone
; Kaapvaal Craton
; South Africa
; Witwatersrand
英文摘要: Plate tectonics plays a vital role in the evolution of our planet. Geochemical analysis of Earth's oldest continental crust suggests that subduction may have begun episodically about 3.8 to 3.2 billion years ago, during the early Archaean or perhaps more than 3.8 billion years ago, during the Hadean. Yet, mantle rocks record evidence for modern-style plate tectonics beginning only in the late Archaean, about 3 billion years ago. Here we analyse the nitrogen abundance, as well as the nitrogen and carbon isotopic signatures of Archaean placer diamonds from the Kaapvaal craton, South Africa, which formed in the upper mantle 3.1 to 3.5 billion years ago. We find that the diamonds have enriched nitrogen contents and isotopic compositions compared with typical mantle values. This nitrogen geochemical fingerprint could have been caused by contamination of the mantle by nitrogen-rich Archaean sediments. Furthermore, the carbon isotopic signature suggests that the diamonds formed by reduction of an oxidized fluid or melt. Assuming that the Archaean mantle was more reduced than the modern mantle, we argue that the oxidized components were introduced to the mantle by crustal recycling at subduction zones. We conclude, on the basis of evidence from mantle-derived diamonds, that modern-style plate tectonics operated as early as 3.5 billion years ago. © 2016 Macmillan Publishers Limited. All rights reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/106056
Appears in Collections: 气候减缓与适应 科学计划与规划
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作者单位: School of Geosciences, University of the Witwatersrand, Private Bag 3, Wits, Johannesburg, South Africa; De Beers Group of Companies, Corporate HeadquartersWest Campus, 59 Crownwood Road, Johannesburg, South Africa; Department of Geology, University of Johannesburg, PO Box 524, Auckland Park, South Africa; Canadian Centre for Isotopic Microanalysis, University of Alberta, Edmonton, AB, Canada
Recommended Citation:
Smart K.A.,Tappe S.,Stern R.A.,et al. Early Archaean tectonics and mantle redox recorded in Witwatersrand diamonds[J]. Nature Geoscience,2016-01-01,9(3)