Early Neoproterozoic accretionary assemblage in the Cathaysia Block: Geochronological, Lu–Hf isotopic and geochemical evidence from granitoid gneisses | |
Yuejun Wang; Yuzhi Zhang; Weiming Fan; Hongyan Geng; Heping Zou; Xianwu Bi | |
2014 | |
Source Publication | Precambrian Research
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Volume | 249Pages:144-161 |
Abstract | The South China Block (SCB) is composed of the Yangtze Block in the northwest and the Cathysia Block in the southeast. The earliest Neoproterozoic granitic rocks in the SCB are important for our understanding of the tectonic regime and location of this ancient continent in relation to the Rodinia supercontinent. However, such rocks have rarely been reported for the Cathaysia Block so far. In this study, six granitic gneisses from the Wuyi-Yunkai domain gave zircon U–Pb ages of 985–913 Ma, indicating the presence of the early Neoproterozoic granitic magmatism in the Cathaysia interior. These granitic gneisses are peraluminous with high FeOt, MgO, TiO2 and CaO/Na2O but low SiO2, Al2O3/TiO2, Al2O3/(MgO + FeOt) and Rb/Sr ratios. They show steep REE chondrite-normalized patterns with δEu values of 0.35–0.70. These samples have strongly negative Ba, Sr, Nb-Ta, P and Ti anomalies in primitive mantle-normalized diagrams, and ɛNd(t) values of −9.54 to −3.81, similar to those of the Kwangsian granitic rocks and Precambrian volcanosedimentary package in the Cathysia Block. The zircon grains with the earliest Neoproterozoic age gave ɛHf(t) values of −9.64 to +2.78 with the peak values at −2.5 and −7.5, and Hf model ages of 1.35–2.00 Ga with the two-peaks of 1.57 Ga and 1.75 Ga, respectively. These data suggest that the granitic gneisses originated dominantly from a binary mixing of metapelitic and metaigneous components, with insignificant input of juvenile materials. We consider that these rocks are closely related to the closure of the earliest Neoproterozoic (∼980 Ma) Wuyi-Yunkai back-arc basin in an accretionary continental margin setting. In combination with other data, it is proposed that the previously-defined Cathaysia block might consist of various sub-blocks separated by the arc-back-arc basin prior to the early Neoproterozoic period. The Wuyi-Yunkai arc-back-arc system was finally closed at ∼920 Ma, significantly younger than the classical Grenvillian Orogenic event, and thus the SCB was located on the margin of the Rodinia supercontinent. |
Keyword | Zircon U–pb Geochronology Lu–hf Isotopic Composition Geochemistry Early Neoproterozoic Granitic Gneiss Accretionary Assemblage Cathaysia |
Indexed By | SCI |
Language | 英语 |
Document Type | 期刊论文 |
Identifier | http://ir.gyig.ac.cn/handle/42920512-1/9381 |
Collection | 矿床地球化学国家重点实验室 |
Affiliation | 1.Department of Earth Sciences, Sun Yat-Sen University, Guangzhou 510275, China 2.Guangdong Provincial Key Laboratory of Mineral Resources and Geological Processes, Guangzhou 510275, China 3.State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China 4.Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China 5.Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China |
Recommended Citation GB/T 7714 | Yuejun Wang;Yuzhi Zhang;Weiming Fan;Hongyan Geng;Heping Zou;Xianwu Bi. Early Neoproterozoic accretionary assemblage in the Cathaysia Block: Geochronological, Lu–Hf isotopic and geochemical evidence from granitoid gneisses[J]. Precambrian Research,2014,249:144-161. |
APA | Yuejun Wang;Yuzhi Zhang;Weiming Fan;Hongyan Geng;Heping Zou;Xianwu Bi.(2014).Early Neoproterozoic accretionary assemblage in the Cathaysia Block: Geochronological, Lu–Hf isotopic and geochemical evidence from granitoid gneisses.Precambrian Research,249,144-161. |
MLA | Yuejun Wang;Yuzhi Zhang;Weiming Fan;Hongyan Geng;Heping Zou;Xianwu Bi."Early Neoproterozoic accretionary assemblage in the Cathaysia Block: Geochronological, Lu–Hf isotopic and geochemical evidence from granitoid gneisses".Precambrian Research 249(2014):144-161. |
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