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http://www.igeodata.org/handle/20.500.11758/345
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DC 字段 | 值 | 语种 |
---|---|---|
所有者 | Alfred Kröner | - |
所有者 | J. Elis Hoffmann | - |
所有者 | Hangqiang Xie | - |
所有者 | Carsten Münker | - |
所有者 | Ernst Hegner | - |
所有者 | Yusheng Wan | - |
所有者 | Axel Hofmann | - |
所有者 | Dunyi Liu | - |
所有者 | Jinhui Yang | - |
获取日期 | 2017-03-07T03:24:44Z | - |
获取日期 | 2017-03-07T03:24:44Z | - |
首次发表日期 | 2014-07 | - |
引用地址 | http://www.igeodata.org/handle/20.500.11758/345 | - |
摘要 | We report zircon ages, Hf-in-zircon isotopes as well as whole-rock geochemistry and Hf–Nd isotopic systematics for Palaeoarchaean grey gneisses of the Ancient Gneiss Complex of Swaziland, the oldest components of the Kaapvaal craton, southern Africa. The Hf-in-zircon isotopic compositions in these compositionally heterogeneous, multicomponent, migmatitic gneisses are highly variable, even in the oldest zircons dating back to 3.66 Ga, suggesting growth of zircon from melts representing a mix of juvenile and anatectic material derived from differentiated continental crust of Eoarchean to late Hadean age. In contrast, the initial Nd and Hf whole-rock isotopic compositions are frequently not in agreement with the Hf-in-zircon data that mostly show approximately chondritic initial values for Nd and strongly radiogenic initial values for Hf. We consider it likely that both the Lu–Hf and Sm–Nd whole-rock isotopic systems were disturbed and partly reset during later episodes of partial melting and crustal reworking, most likely during a pervasive 3.2 Ga tectono-metamorphic event. Primitive mantle-normalized trace element patterns show the variable influence of residual plagioclase and garnet in the sources as well as high contents of strongly incompatible elements. In conjunction with the Hf-in-zircon isotopic data the trace element contents are best explained by the incorporation of older continental crustal material into the sources of the grey gneisses. Our data support evidence from other Palaeoarchean terranes that crustal recycling, as seen in even the oldest crustal components, played an important role in early continental evolution. Rocks previously classified as a subduction- related tonalite–trondhjemite–granodiorite suite are complex, and their chemistry alone cannot be used to reconstruct tectonic settings. | zh_CN |
语种 | en | zh_CN |
出版者 | Institute of Geology Chinese Academy of Geological Sciences | zh_CN |
主题关键词 | Grey gneiss | zh_CN |
主题关键词 | Palaeoarchaean | zh_CN |
主题关键词 | Kaapvaal craton | zh_CN |
主题关键词 | Hf–Nd isotopes | zh_CN |
成果名称 | Generation of early Archaean grey gneisses through melting of older crust in the eastern Kaapvaal craton, southern Africa | zh_CN |
类型 | Book | zh_CN |
所属集合: | 科技成果 |
文件中的条目:
条目 | 描述 | 大小 | 格式 | |
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Generation of early Archaean grey gneisses through melting of oldercrust in the eastern Kaapvaal craton.pdf | 5.54 MB | Adobe PDF |
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