DOI: 10.1016/j.epsl.2018.01.034
Scopus记录号: 2-s2.0-85044721438
论文题名: Two distinct origins for Archean greenstone belts
作者: Smithies R.H. ; Ivanic T.J. ; Lowrey J.R. ; Morris P.A. ; Barnes S.J. ; Wyche S. ; Lu Y.-J.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 487 起始页码: 106
结束页码: 116
语种: 英语
英文关键词: Archean
; crustal evolution
; greenstone chemistry
; Th/Yb–Nb/Yb plot
; Western Australia
Scopus关键词: Alkalinity
; Basalt
; Economic geology
; Granite
; Lithology
; Stratigraphy
; Volcanoes
; Archean
; Archean greenstone belts
; Crustal evolution
; Granite magmatism
; Mantle derived magmas
; Subduction process
; Western Australia
; Yilgarn cratons
; Tectonics
; andesite
; Archean
; crust-mantle boundary
; crustal evolution
; geochemistry
; geological record
; granite
; greenstone belt
; magmatism
; mantle source
; stratigraphy
; subduction zone
; volcanic rock
; Australia
; Pilbara Block
; Western Australia
; Yilgarn Block
英文摘要: Applying the Th/Yb–Nb/Yb plot of Pearce (2008) to the well-studied Archean greenstone sequences of Western Australia shows that individual volcanic sequences evolved through one of two distinct processes reflecting different modes of crust–mantle interaction. In the Yilgarn Craton, the volcanic stratigraphy of the 2.99–2.71 Ga Youanmi Terrane mainly evolved through processes leading to Th/Yb–Nb/Yb trends with a narrow range of Th/Nb (‘constant-Th/Nb’ greenstones). In contrast, the 2.71–2.66 Ga volcanic stratigraphy of the Eastern Goldfields Superterrane evolved through processes leading to Th/Yb–Nb/Yb trends showing a continuous range in Th/Nb (‘variable-Th/Nb’ greenstones). Greenstone sequences of the Pilbara Craton show a similar evolution, with constant-Th/Nb greenstone evolution between 3.13 and 2.95 Ga and variable-Th/Nb greenstone evolution between 3.49 and 3.23 Ga and between 2.77 and 2.68 Ga. The variable-Th/Nb trends dominate greenstone sequences in Australia and worldwide, and are temporally associated with peaks in granite magmatism, which promoted crustal preservation. The increasing Th/Nb in basalts correlates with decreasing εNd, reflecting variable amounts of crustal assimilation during emplacement of mantle-derived magmas. These greenstones are typically accompanied in the early stages by komatiite, and can probably be linked to mantle plume activity. Thus, regions such as the Eastern Goldfields Superterrane simply developed as plume-related rifts over existing granite–greenstone crust – in this case the Youanmi Terrane. Their Th/Nb trends are difficult to reconcile with modern-style subduction processes. The constant-Th/Nb trends may reflect derivation from a mantle source already with a high and constant Th/Nb ratio. This, and a lithological association including boninite-like lavas, basalts, and calc-alkaline andesites, all within a narrow Th/Nb range, resembles compositions typical of modern-style subduction settings. These greenstones are very rare, and were probably only preserved when fortuitously stabilised by granitic magmatism related to the evolution of later variable-Th/Nb greenstones. The rarity of constant-Th/Nb trends suggests that either processes forming them never dominated Archean greenstone evolution, or that such greenstones simply were rarely preserved. Metamorphic mobility of Th renders the Th/Yb–Nb/Yb plot inappropriate for interpreting Eoarchean greenstone units worldwide. Nevertheless, such sequences appear dominated by volcanic rocks that, in modern settings, reflect only the embryonic or initiation stages of subduction. They probably record subduction failure rather than anything resembling modern-style subduction. © 2018 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/110009
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: Geological Survey of Western Australia, Mineral House, 100 Plain Street, East Perth, WA 6004, Australia; School of Geosciences, University of SydneyNSW 2006, Australia; Earth Science and Resource Engineering, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Kensington, WA 6151, Australia; Centre for Exploration Targeting, Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS), School of Earth Sciences, The University of Western Australia, Crawly, WA 6009, Australia
Recommended Citation:
Smithies R.H.,Ivanic T.J.,Lowrey J.R.,et al. Two distinct origins for Archean greenstone belts[J]. Earth and Planetary Science Letters,2018-01-01,487