Petrogenesis and Geological Implications of the Oligocene;Chongmuda-Mingze Adakite-Like Intrusions and Their Mafic Enclaves,;Southern Tibet

	Petrogenesis and Geological Implications of the Oligocene;Chongmuda-Mingze Adakite-Like Intrusions and Their Mafic Enclaves,;Southern Tibet
	Zheng, Yuan-Chuan; Hou, Zeng-Qian; Li, Wei; Liang, Wei; Huang, Ke-Xian; Li, Qiu-Yun; Sun, Qing-Zhong; Fu, Qiang; Zhang, Song
刊名	JOURNAL OF GEOLOGY
	2012
卷号	120 期号:6 页码:647-669
ISSN号	031NY
英文摘要	The Oligocene to the Miocene was a critical period for the growth of the Tibetan Plateau. This growth is commonly considered to have been controlled by deep geodynamic processes. The ultrapotassic and adakite-like igneous rocks that developed during this period offer constraints on these deep-seated processes in southern Tibet. Whole-rock geochemistry, U-Pb zircon geochronology, and in situ zircon Hf isotopes have been determined for the mafic enclaves and host adakite-like granitoids in the Oligocene Chongmuda-Mingze intrusive complex of southern Tibet. The host rocks, including granodiorite and monzogranite, are mainly high-K and calc-alkaline in composition. Their whole-rock geochemistry (low MgO, Ni, and Cr contents; negative epsilon(Nd(t)) values [-2.5 to -3.4]; and low Sr-87/Sr-86((i)) values [0.7061-0.7066]) and in situ zircon epsilon(Hf(t)) values (0.6-6.1) indicate that they were derived by partial melting of a juvenile lower crust, implying that the southern Tibetan crust was already thickened to up to 50 km before similar to 30 Ma. Mafic enclaves show typical igneous textures, acicular apatites, backveining structures, quenched margins, and crystallization ages identical to those of the host granites, indicating that they are of magmatic origin. The mafic enclaves have high-K to shoshonitic metaluminous compositions and are strongly enriched in large-ion lithophile elements and light rare earth elements, are depleted in high-field-strength elements, have negative epsilon(Nd(t)) values (-2.6 to -4.9), have relatively high Sr-87/Sr-86 (i) values (0.7060-0.7072), and have low zircon epsilon(Hf(t)) values (2.3-5.5), indicating that they were derived from a relatively enriched lithospheric mantle source. Our new data, together with previously published work, lead us to suggest that deep geodynamic processes below the southern Tibetan region during the Oligocene to the Miocene were characterized by convective removal of the lower lithosphere. Upwelling of the asthenosphere induced by the delamination of the southern Tibetan lithospheric root could have supplied heat to induce anatexis of the residual lithosphere of southern Tibet, generating the adakite-like rocks and related mafic enclaves there.
学科主题	火成岩岩石学
WOS关键词	INDO-ASIAN COLLISION ; ZIRCON U-PB ; HF ISOTOPIC COMPOSITIONS ; THICKENED ; LOWER CRUST ; MANTLE BENEATH TIBET ; EAST-WEST EXTENSION ; SR-ND-PB ; CONTINENTAL COLLISION ; TRACE-ELEMENT ; POSTCOLLISIONAL MAGMATISM
WOS研究方向	Geology
语种	英语
出版者	This study was supported by grants from the National Natural Science;Foundation of China (238925) and the Ministry of Science and Technology;of China (973 project 2011CB403100). We are deeply indebted to D. C. Zhu;of China University of Geosciences (Beijing) for his incisive reviews,;valuable comments, and suggestions to improve an earlier draft of this;manuscript. We are also most grateful to Z. D. Zhao and J. Richards for;critical and constructive reviews of this manuscript.
WOS记录号	WOS:000310650100004
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/39826]
专题	中国地质科学院地质研究所
作者单位	Chinese Acad Geol Sci, Inst Geol, Beijing 100037, Peoples R China.
推荐引用方式 GB/T 7714	Zheng, Yuan-Chuan,Hou, Zeng-Qian,Li, Wei,et al. Petrogenesis and Geological Implications of the Oligocene;Chongmuda-Mingze Adakite-Like Intrusions and Their Mafic Enclaves,;Southern Tibet[J]. JOURNAL OF GEOLOGY,2012,120(6):647-669.
APA	Zheng, Yuan-Chuan.,Hou, Zeng-Qian.,Li, Wei.,Liang, Wei.,Huang, Ke-Xian.,...&Zhang, Song.(2012).Petrogenesis and Geological Implications of the Oligocene;Chongmuda-Mingze Adakite-Like Intrusions and Their Mafic Enclaves,;Southern Tibet.JOURNAL OF GEOLOGY,120(6),647-669.
MLA	Zheng, Yuan-Chuan,et al."Petrogenesis and Geological Implications of the Oligocene;Chongmuda-Mingze Adakite-Like Intrusions and Their Mafic Enclaves,;Southern Tibet".JOURNAL OF GEOLOGY 120.6(2012):647-669.