Origin of Late Oligocene adakitic intrusives in the southeastern Lhasa terrane Evidence from in situ zircon U-Pb dating, Hf-O isotopes, and whole-rock geochemistry

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	Origin of Late Oligocene adakitic intrusives in the southeastern Lhasa terrane Evidence from in situ zircon U-Pb dating, Hf-O isotopes, and whole-rock geochemistry
	Zheng, YC (Zheng, Yuan-Chuan)9; Hou, ZQ (Hou, Zeng-Qian); Li, QY (Li, Qiu-Yun); Sun, QZ (Sun, Qing-Zhong); Liang, W (Liang, Wei); Fu, Q (Fu, Qiang); Li, W (Li, Wei); Huang, KX (Huang, Ke-Xian)
刊名	LITHOS
	2012
卷号	148 页码:296-311
关键词	U-Pb zircon age Geochemistry In situ zircon Hf-O isotopes Adakitic rocks Lhasa terrane
ISSN号	0024-4937
英文摘要	We describe the whole-rock geochemistry, biotite Ar-Ar and zircon U-Pb geochronology, and in situ Hf-O isotopic compositions of the Linzhi two-mica granitoid in the southeastern Lhasa terrane. The granitoids are calc-alkaline to high-K calc-alkaline in composition, and they have geochemical affinities with adakites. The whole-rock geochemistry, with high SiO2 and Al2O3 contents, low MgO, Cr, and Ni contents, low Mg# values, negative epsilon(Nd(t)) (-6.2 to -2.9). and low Sr-87/Sr-86((i)) (0.7059-0.7074), together with the in situ zircon Hf-O isotopic data (epsilon(Hf(t)) = 2.7 to 2.7; delta O-18 = 7.2 parts per thousand-8.8 parts per thousand), indicates that the granitoid was derived mainly from the partial melting of a rejuvenated lower crust underneath the Lhasa terrane. This lower crust was dominated by ancient crustal material with the minor involvement of juvenile mantle inputs (<55%). SIMS zircon U-Pb analyses of two samples indicate that the crystallization of the Linzhi granitoid took place around 26 Ma, implying that the crust of the Lhasa terrane was already thickened up to 50 km prior to emplacement of the adakitic rocks. Ar-40/Ar-39 ages for biotites, and the presence of magmatic epidote, suggest the granitoid was intruded at mid-crustal depths, indicating that the eastern Lhasa terrane experienced a pulse of rapid uplift in the interval from 26 to 22 Ma. The geochemical features of the Linzhi adakitic rocks are significantly different from those of Eocene adakitic rocks from the north Himalayan belt, and this suggests that we can rule out the possibility of crustal thickening in the eastern part of Lhasa terrane, caused by impingement of the Indian lower crust. Post-collisional (26-10 Ma) adakitic rocks occur within an E-W-trending magmatic belt that runs parallel to the Yarlung-Tsangpo suture in the Lhasa terrane. These rocks have distinctive variations in geochemistry along the strike of the Lhasa terrane, indicating that the lower crust is isotopically heterogeneous from west to east along the terrane. These geochemical variations probably result from variable degrees of input, along strike, of juvenile mantle-derived melts into an old lower crust. The middle part of the Lhasa terrane is marked by a juvenile lower crust that contains large amounts of mantle-derived melt, underplated during Neo-Tethyan oceanic crust subduction. In contrast, the lower crust below the western and eastern parts of the terrane is relatively ancient. Therefore, crustal thickening caused by underplating of mantle-derived magmas could play an important role in the middle segment of the terrane, whereas crustal compression and shortening as a result of the collision of the Indian and Asian plates could be the major cause for crustal thickening in the western and eastern segments. (C) 2012 Elsevier B.V. All rights reserved.
学科主题	火成岩岩石学
WOS关键词	BENEATH SOUTHERN TIBET ; CONTINENTAL COLLISION ZONES ; THICKENED LOWER CRUST ; INDIA-ASIA COLLISION ; EAST-WEST EXTENSION ; TRACE-ELEMENT ; LU-HF ; TECTONIC IMPLICATIONS ; DEPLETED MANTLE ; SUBDUCTED SLAB
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000308055800020
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/39816]
专题	中国地质调查局
作者单位	1.[Zheng, Yuan-Chuan 2.Hou, Zeng-Qian 3.Li, Qiu-Yun 4.Sun, Qing-Zhong 5.Liang, Wei 6.Fu, Qiang 7.Li, Wei 8.Chinese Acad Geol Sci, Inst Geol, Beijing 100037, Peoples R China 9.中国地质科学院地质研究所
推荐引用方式 GB/T 7714	Zheng, YC ,Hou, ZQ ,Li, QY ,et al. Origin of Late Oligocene adakitic intrusives in the southeastern Lhasa terrane Evidence from in situ zircon U-Pb dating, Hf-O isotopes, and whole-rock geochemistry[J]. LITHOS,2012,148:296-311.
APA	Zheng, YC .,Hou, ZQ .,Li, QY .,Sun, QZ .,Liang, W .,...&Huang, KX .(2012).Origin of Late Oligocene adakitic intrusives in the southeastern Lhasa terrane Evidence from in situ zircon U-Pb dating, Hf-O isotopes, and whole-rock geochemistry.LITHOS,148,296-311.
MLA	Zheng, YC ,et al."Origin of Late Oligocene adakitic intrusives in the southeastern Lhasa terrane Evidence from in situ zircon U-Pb dating, Hf-O isotopes, and whole-rock geochemistry".LITHOS 148(2012):296-311.