成果归属作者：

朱弟成 ; 莫宣学 ; 赵志丹

成果归属机构：

地球科学与资源学院

作者：

Zhu, Di-Cheng ; Mo, Xuan-Xue ; Niu, Yaoling ; Zhao, Zhi-Dan ; Wang, Li-Quan ; Liu, Yong-Sheng ; Wu, Fu-Yuan

单位：

China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China;China Univ Geosci, Sch Earth Sci & Resources, Beijing 100083, Peoples R China;Univ Durham, Dept Earth Sci, Durham DH1 3LE, England;Chengdu Inst Geol & Mineral Resources, Chengdu 610082, Peoples R China;China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Wuhan 430074, Peoples R China;Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China

关键词：

Bulk-rock geochemistry; Zircon U-Pb dating and Hf isotope; Petrogenesis; Early Cretaceous igneous rocks; Slab break-off; Bangong-Nujiang Tethyan Ocean; Tectonomagmatic evolution; Lhasa micro-continental block; Tibet

摘要：

Bulk-rock major and trace element, Sr-Nd isotope, zircon U-Pb and Hf-isotope data are reported for Early Cretaceous igneous rocks sampled along an east-west traverse through the central Lhasa subterrane (E80 degrees 00'-E89 degrees) in southern Tibet. These results offer new insights into the pre-Cenozoic geology and tectonomagmatic evolution of the Lhasa Terrane, and provide boundary conditions for the origin and evolution of the Tibetan Plateau. Our new data, together with data from the literature indicate that the Early Cretaceous magmatism in the central Lhasa subterrane lasted for a long period (similar to 143-102 Ma) with a magmatic flare-up at similar to 110 Ma. The latter is accompanied by mafic magmatism in this terrane. The silicic rocks are metaluminous to peraluminous, and enriched in Rb, Th, and U, and depleted in Ba, Nb, Ta, Sr, P, and Ti, with varying initial Sr-87/Sr-86 (0.7073-0.7209), negative epsilon(Nd)(t) (- 13.7 to - 4.6), and negative to positive zircon epsilon(Hf)(t). The andesitic and dioritic enclaves are characterized by initial Sr-87/Sr-86 of 0.7088-0.7148, epsilon(Nd)(t) of - 9.9 to - 7.8, and zircon epsilon(Hf)(t) of - 9.5 to - 0.2, similar to those of the 110 +/- 3 Ma silicic rocks. The bulk-rock Sr and Nd isotopic data and zircon epsilon(Hf)(t) values indicate an increased contribution of a mantle component in the generation of the Early Cretaceous igneous rocks in the central Lhasa subterrane at similar to 110 Ma. Available bulk-rock Nd- and zircon Hf-isotope data indicate that the crust of the central Lhasa subterrane, at least its oldest elements, was emplaced during the Archean. This further indicates that the central Lhasa subterrane with ancient basement must have been a micro-continental block (i.e., the Lhasa micro-continental block) extending in an east-west direction for > 700 km (E82 degrees-E89 degrees) with a width of similar to 100 km. The contemporaneous presence of S-type (more crustal source) and I-type (significant mantle input) melts of the Early Cretaceous igneous rocks in this subterrane are interpreted as the consequences of varying extents of interactions between the existing continental crust and mantle-derived melts (including crustal anatexis). We suggest that the mantle-derived melts resulted from southward subduction of the Bangong-Nujiang Ocean seafloor in a syncollisional setting related to the Lhasa-Qiangtang collision, and that the magmatic flare-up with strong mantle input at similar to 110 Ma was genetically associated with the slab break-off of this subducting seafloor. (C) 2009 Elsevier B.V. All rights reserved.

基金：

China Postdoctoral Special Science Foundation; National Key Project for Basic Research of China [2006CB701402, 2009CB421002]; National Natural Science Foundation of China [40830317, 40973026, 40873023]; Chinese 111 Project [B07011]; China Geological Survey

语种：

英文

DOI：

10.1016/j.chemgeo.2009.09.008

来源：

CHEMICAL GEOLOGY,2009(3-4):298-312.

出版日期：

2009-11-30

提交日期：

2017-12-14

引用参考：

Zhu, Di-Cheng; Mo, Xuan-Xue; Niu, Yaoling; Zhao, Zhi-Dan; Wang, Li-Quan; Liu, Yong-Sheng; Wu, Fu-Yuan. Geochemical investigation of Early Cretaceous igneous rocks along an east-west traverse throughout the central Lhasa Terrane, Tibet[J]. CHEMICAL GEOLOGY,2009(3-4):298-312.