Petrogenesis of the Early Eocene adakitic rocks in the Napuri area, southern Lhasa: Partial melting of thickened lower crust during slab break-off and implications for crustal thickening in southern Tibet

doi:10.1016/j.lithos.2014.02.011

	Petrogenesis of the Early Eocene adakitic rocks in the Napuri area, southern Lhasa: Partial melting of thickened lower crust during slab break-off and implications for crustal thickening in southern Tibet
	Ma, Lin 1,2; Wang, Bao-Di 3,4; Jiang, Zi-Qi 1; Wang, Qiang 1; Li, Zheng-Xiang 5,6; Wyman, Derek A.7; Zhao, Shou-Ren 4; Yang, Jin-Hui 8; Gou, Guo-Ning 1,2; Guo, Hai-Feng 1,2
刊名	LITHOS
	2014-05-01
卷号	196 页码:321-338
关键词	Adakitic rocks Lower crustal melting Crustal thickening Slab breakoff Tibet
ISSN号	0024-4937
DOI	10.1016/j.lithos.2014.02.011
文献子类	Article
英文摘要	Cenozoic adakitic rocks in the Lhasa block (southern Tibet) have been widely used to trace the lateral extent of crustal thickening. However, their petrogenesis remains controversial. Here, we report geochronological and geochemical data for the Napuri intrusive rocks in the core area of the Quxu batholith, southern Lhasa. Zircon U-Pb dating suggests that they were generated at approximately 48 Ma. The studied samples show significant geochemical variations, manifested by the coexistence of three types of igneous rocks. Groups I and II rocks exhibit variable and high SiO2 (66.4-73.9 wt.%), high Al2O3 (14.0-17.4 wt.%), K2O (3.9-53 wt.%), Sr (273-718 ppm) and Sr/Y (183 to 813) values, and low Y (3.6 to 16 ppm), heavy rare earth element (REE) (e.g., Yb = 0.48 to 1.8 ppm), MgO (0.4-1.0 wt.%), Cr (2.9-7.4 ppm) and Ni (1.6-4.5 ppm) contents, which are similar to those of thickened lower crust-derived adakitic rocks. The Group I rocks show higher Sr/Y (77.5-81.3) ratios and lower total REE (55.5-63.2 ppm) contents with clearly positive Eu and Sr anomalies, whereas the Group II rocks have relatively lower Sr/Y (18.3-65.7) ratios and higher total REE (115-375 ppm) contents with negligible or slightly negative Eu and Sr anomalies. Group III rocks have the highest SiO2 (74.5-76.0 wt.%), Y (17.0-23.7 ppm) and Yb (2.91-330 ppm) contents, and the lowest Al2O3 (12.5-13.2 wt.%), Sr (81.3-141 ppm) and Sr/Y (4.8-5.9) values with distinctly negative Eu and Sr anomalies. Compared with the Jurassic-Cretaceous granitoids in southern Lhasa, the relative enrichment in Sr-Nd-Hf isotopic compositions ((Sr-87/Sr-86)(i) = 0.7049-0.7055, epsilon(Nd)(t) = 0.3 +/- 0.7 and epsilon(Hf)(t)(zircon) = +3.6 +/- 11.4) for the Napuri intrusive rocks indicates that they likely contained Indian continental components. The Group I and Group II rocks most probably originated from thickened mafic lower crust (amphibolite eclogites or garnet amphibolites) with garnet + rutile +/- plagioclase as residual minerals in the source at >1.5 GPa, corresponding to depths of >50 km, and Group III rocks were probably generated by fractional crystallization of plagioclase from the adakitic magmas. Taking into account the narrow linear nature of the Eocene magmatic belt and reported synchronous asthenosphere-derived basaltic rocks in southern Lhasa, we suggest that upwelling asthenosphere triggered by the break-off of subducted Neo-Tethyan slab probably provided the required thermal conditions for lower crustal melting. The identification of Indian continental components in the Napuri intrusive rocks probably indicates that the Asia-India collision had taken place prior to their emplacement. The dramatic changes in the (La/Yb)(N) ratios and epsilon(Nd)(t) and epsilon(Hf)(t) values of magmatic rocks in the Gangdese area at ca. 51-46 Ma indicate that the Cenozoic crustal thickening associated with the indentation of the Indian continent began in the Early Eocene (ca. 51-46 Ma) at the latest. (C) 2014 Elsevier B.V. All rights reserved.
WOS关键词	U-PB GEOCHRONOLOGY ; CONTINENTAL COLLISION ZONES ; UNDERPLATED BASALTIC CRUST ; HF ISOTOPE CONSTRAINTS ; HIGH-MG ANDESITES ; GANGDESE BATHOLITH ; VOLCANIC-ROCKS ; ULTRAPOTASSIC MAGMATISM ; GEOCHEMICAL CONSTRAINTS ; TECTONIC EVOLUTION
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000336347800021
资助机构	Chinese Academy of Sciences(XDB03010600) ; Chinese Academy of Sciences(XDB03010600) ; National Natural Science Foundation of China(41025006 ; National Natural Science Foundation of China(41025006 ; Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS 135 project)(Y234021001) ; Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS 135 project)(Y234021001) ; 41121002 ; 41121002 ; 41073033) ; 41073033) ; Chinese Academy of Sciences(XDB03010600) ; Chinese Academy of Sciences(XDB03010600) ; National Natural Science Foundation of China(41025006 ; National Natural Science Foundation of China(41025006 ; Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS 135 project)(Y234021001) ; Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS 135 project)(Y234021001) ; 41121002 ; 41121002 ; 41073033) ; 41073033) ; Chinese Academy of Sciences(XDB03010600) ; Chinese Academy of Sciences(XDB03010600) ; National Natural Science Foundation of China(41025006 ; National Natural Science Foundation of China(41025006 ; Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS 135 project)(Y234021001) ; Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS 135 project)(Y234021001) ; 41121002 ; 41121002 ; 41073033) ; 41073033) ; Chinese Academy of Sciences(XDB03010600) ; Chinese Academy of Sciences(XDB03010600) ; National Natural Science Foundation of China(41025006 ; National Natural Science Foundation of China(41025006 ; Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS 135 project)(Y234021001) ; Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS 135 project)(Y234021001) ; 41121002 ; 41121002 ; 41073033) ; 41073033)
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/85225]
专题	中国科学院地质与地球物理研究所
通讯作者	Wang, Qiang
作者单位	1.Chinese Acad Sci, Guangzhou Inst Geochem, State Key Lab Isotope Geochem, Guangzhou 510640, Guangdong, Peoples R China 2.Univ Chinese Acad Sci, Beijing 100049, Peoples R China 3.Chengdu Inst Geol & Mineral Resources, Chengdu 610081, Peoples R China 4.Geol Survey Party, Inst Autonomous Reg, Lhasa 851400, Tibet, Peoples R China 5.Curtin Univ, ARC Ctr Excellence Core Crust Fluid Syst CCFS, Perth, WA 6845, Australia 6.Curtin Univ, Inst Geosci Res TIGeR, Dept Appl Geol, Perth, WA 6845, Australia 7.Univ Sydney, Sch Geosci, Sydney, NSW 2006, Australia 8.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Ma, Lin,Wang, Bao-Di,Jiang, Zi-Qi,et al. Petrogenesis of the Early Eocene adakitic rocks in the Napuri area, southern Lhasa: Partial melting of thickened lower crust during slab break-off and implications for crustal thickening in southern Tibet[J]. LITHOS,2014,196:321-338.
APA	Ma, Lin.,Wang, Bao-Di.,Jiang, Zi-Qi.,Wang, Qiang.,Li, Zheng-Xiang.,...&Guo, Hai-Feng.(2014).Petrogenesis of the Early Eocene adakitic rocks in the Napuri area, southern Lhasa: Partial melting of thickened lower crust during slab break-off and implications for crustal thickening in southern Tibet.LITHOS,196,321-338.
MLA	Ma, Lin,et al."Petrogenesis of the Early Eocene adakitic rocks in the Napuri area, southern Lhasa: Partial melting of thickened lower crust during slab break-off and implications for crustal thickening in southern Tibet".LITHOS 196(2014):321-338.