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Eocene supra-subduction zone mafic magmatism in the Sibumasu Block of SW Yunnan: Implications for Neotethyan subduction and India–Asia collision
Yuejun Wang;  Limin Zhang;  Peter A. Cawood;  Liyan Ma;  Weiming Fan;  Aimei Zhang;  Yuzhi Zhang;  Xianwu Bi
2014
Source PublicationLithos, Volumes
Volume206–207Pages:384-399
Abstract

Geochemical and isotopic data for metabasic rocks in NW Yunnan constrain the nature of the mantle source beneath the East Himalayan Syntaxis during the Neotethyan subduction and the timing of initial collision between India and Asia. Our results indicate that these mafic rocks crystallized at 50–55 Ma and were metamorphosed at ~ 39 Ma, contemporaneous with magmatic flare-ups and high-grade metamorphism in South Tibet. The mafic rocks in NW Yunnan are divisible into three groups. Group 1, from Nabang, shows geochemical affinity to a MORB-like source modified by the recycled component with εNd(t) of + 5.1 to + 9.5 and εHf(t) of + 5.1 to + 11.6, and resembles back-arc basin basalt. Group 2 is mainly from Jinzhouzhai and Tongbiguan to the east of Group 1, and is marked by high Al2O3, enrichment in LILEs and depletion in HFSEs, along with negative εNd(t) (− 1.1 to − 5.6) and εHf(t) (− 4.6 to − 0.9) values. Group 2 is interpreted to have originated from the lithospheric mantle modified by input from a slab-derived component in a continental arc setting. Group 3, from Nanjingli, is located a considerable distance east from Group 1, and exhibits negative εNd(t) (− 6.7 to − 7.6) and εHf(t) (− 7.1 to − 2.2), and is inferred to be derived from the Tengchong lithospheric mantle but with limited involvement of a slab-derived component. Overall Nd–Hf isotopic compositions show a sharp decrease from Group 1 to Group 2 and then a more subdued decrease to Group 3, with the three groups corresponding to an overall spatial distribution from west to east. Our results suggest that early Eocene magmatism in NW Yunnan represents the eastward continuation of the Gangdese magmatic belt and that the Neotethyan subduction continued until ~ 50 Ma followed by the India–Asia collision. It is proposed that at least two eastward-dipping subduction zones are involved in the Neotethyan suprasubduction system prior to 55 Ma. The sudden decrease in convergence rate in the early Eocene (55–50 Ma), together with the inferred positive buoyancy of the Tengchong lithosphere, stimulated rollback of down-going slab and induced melting of heterogeneous mantle sources to result in a flare-up in magmatic activity.

KeywordEarly Eocene Mafic Rocks Mantle Source Geochronological And Geochemical Constrains Gangdese Belt Neotethyan Suprasubduction Nw Yunnan
Indexed BySCI
Language英语
Document Type期刊论文
Identifierhttp://ir.gyig.ac.cn/handle/42920512-1/9384
Collection矿床地球化学国家重点实验室
Affiliation1.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.Department of Earth Sciences, University of St. Andrews, St. Andrews, UK
4.School of Earth and Environment, University of Western Australia, Crawley, 35 Stirling Highway, Australia
5.College of Earth Sciences, Guilin University of Technology, Guilin 541004, China
6.Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
7.Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China
8.State Key Laboratory of Ore Deport Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
Recommended Citation
GB/T 7714
Yuejun Wang;Limin Zhang;Peter A. Cawood;Liyan Ma;Weiming Fan;Aimei Zhang;Yuzhi Zhang;Xianwu Bi. Eocene supra-subduction zone mafic magmatism in the Sibumasu Block of SW Yunnan: Implications for Neotethyan subduction and India–Asia collision[J]. Lithos, Volumes,2014,206–207:384-399.
APA Yuejun Wang;Limin Zhang;Peter A. Cawood;Liyan Ma;Weiming Fan;Aimei Zhang;Yuzhi Zhang;Xianwu Bi.(2014).Eocene supra-subduction zone mafic magmatism in the Sibumasu Block of SW Yunnan: Implications for Neotethyan subduction and India–Asia collision.Lithos, Volumes,206–207,384-399.
MLA Yuejun Wang;Limin Zhang;Peter A. Cawood;Liyan Ma;Weiming Fan;Aimei Zhang;Yuzhi Zhang;Xianwu Bi."Eocene supra-subduction zone mafic magmatism in the Sibumasu Block of SW Yunnan: Implications for Neotethyan subduction and India–Asia collision".Lithos, Volumes 206–207(2014):384-399.
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