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Zircon U–Pb ages, Hf–O isotopes and whole-rock Sr–Nd–Pb isotopic geochemistry of granitoids in the Jinshajiang suture zone, SW China: Constraints on petrogenesis and tectonic evolution of the Paleo-Te
Jing-Jing Zhu;  Rui-Zhong Hu;  Xian-Wu Bi;  Hong Zhong;  Heng Chen
2011
Source PublicationLithos
Volume126Issue:3–4Pages:248-264
Abstract

The Jinshajiang suture zone, located in the eastern part of the Tethyan tectonic domain, is noticeable for a large-scale distribution of Late Jurassic to Triassic granitoids. These granitoids were genetically related to the evolution of the Paleo-Tethys Ocean. Beiwu, Linong and Lunong granitoids occur in the middle zone of the Jinshajiang Suture Zone, and possess similar geochemical features, indicating that they share a common magma source. SIMS zircon U–Pb dating reveals that the Beiwu, Linong and Lunong granitic intrusions were emplaced at 233.9± 1.4 Ma (2σ), 233.1± 1.4 Ma (2σ) and 231.0± 1.6 Ma (2σ), respectively. All of these granitoids are enriched in abundances of Si (SiO2t= 65.2–73.5 wt.%), and large-ion lithophile elements (LILEs), but depleted in high field strength elements contents (HFSEs, e.g., Nb, Ta, and Ti). In addition, they have low P2O5 contents (0.06–0.11 wt.%), A/CNK values ([molecular Al2O3/(CaO+Na2O+K2O)], mostly b1.1) and 10,000 Ga/Al ratios (1.7–2.2), consistent with the characteristics of I-type granites. In terms of isotopic compositions, these granitoids have high initial 87Sr/86Sr ratios (0.7078–0.7148), Pb isotopic compositions [(206Pb/204Pb)t=18.213–18.598, (207Pb/204Pb)t= 15.637–15.730 and (208Pb/204Pb)t=38.323–38.791], zircon δ18O values (7.3‰–9.3‰) and negative εNd(t) values (−5.1 to −6.7), suggesting they were predominantly derived from the continental crust. Their Nb/Ta ratios (average value= 8.6) are consistent with those of the lower continental crust (LCC). However, variable εHf(t) values (−8.6 to +2.8) and the occurrences of mafic microgranular enclaves (MMEs) suggest that mantle-derived melts and lower crustal magmas were involved in the generation of these granitoids. Moreover, the high Pb isotopic ratios and elevated zircon δ18O values of these rocks indicate a significant contribution of the upper crustal composition. We propose a model in which the Beiwu, Linong and Lunong granitoids were generated under a late collisional or post-collisional setting. It is possible that this collision was completed before Late Triassic. Decompression induced mantle-derived magmas to be underplated and provided the heat for the anatexis of the crust. Hybrid melts including mantle-derived and the lower crustal magmas were then generated. The hybrid melts thereafter ascended to a shallow depth and resulted in some degree of sedimentary rock assimilation. Such three-component mixing magma source and subsequent fractional crystallization could be responsible for the formation of the Beiwu, Linong and Lunong granitoids. 

KeywordI-type Granite zircon U–pb Dating zircon Hf–o Isotope sr–nd–pb Isotope three-component Mixing paleo-tethys Ocean
Indexed BySCI
Language英语
Document Type期刊论文
Identifierhttp://ir.gyig.ac.cn/handle/42920512-1/8707
Collection矿床地球化学国家重点实验室
Affiliation1.State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
2.The Gradute School of the Chinese Academy of Sciences, Beijing 100039, China
Recommended Citation
GB/T 7714
Jing-Jing Zhu;Rui-Zhong Hu;Xian-Wu Bi;Hong Zhong;Heng Chen. Zircon U–Pb ages, Hf–O isotopes and whole-rock Sr–Nd–Pb isotopic geochemistry of granitoids in the Jinshajiang suture zone, SW China: Constraints on petrogenesis and tectonic evolution of the Paleo-Te[J]. Lithos,2011,126(3–4):248-264.
APA Jing-Jing Zhu;Rui-Zhong Hu;Xian-Wu Bi;Hong Zhong;Heng Chen.(2011).Zircon U–Pb ages, Hf–O isotopes and whole-rock Sr–Nd–Pb isotopic geochemistry of granitoids in the Jinshajiang suture zone, SW China: Constraints on petrogenesis and tectonic evolution of the Paleo-Te.Lithos,126(3–4),248-264.
MLA Jing-Jing Zhu;Rui-Zhong Hu;Xian-Wu Bi;Hong Zhong;Heng Chen."Zircon U–Pb ages, Hf–O isotopes and whole-rock Sr–Nd–Pb isotopic geochemistry of granitoids in the Jinshajiang suture zone, SW China: Constraints on petrogenesis and tectonic evolution of the Paleo-Te".Lithos 126.3–4(2011):248-264.
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