Lamproitic rocks from a continental collision zone: Evidence for recycling of subducted Tethyan oceanic sediments in the mantle beneath southern Tibet

doi:10.1093/petrology/egl080

	Lamproitic rocks from a continental collision zone: Evidence for recycling of subducted Tethyan oceanic sediments in the mantle beneath southern Tibet
	Gao, Yongfeng ; Hou, Zengqian ; Kamber, Balz S.; Wei, Ruihua ; Meng, Xiangjin ; Zhao, Rongsheng
刊名	JOURNAL OF PETROLOGY
	2007-04-01
卷号	48 期号:4 页码:729-752
关键词	lamproites subducted oceanic sediment Tibetan active continental collision belt
ISSN号	0022-3530
DOI	10.1093/petrology/egl080
文献子类	Article
英文摘要	Major and trace element, Sr-Nd-Pb isotope and mineral chemical data are presented for newly discovered ultrapotassic lavas in the Tangra Yumco-Xuruco graben in southern Tibet. The ultrapotassic lavas are characterized by high MgO, K2O and TiO2, low Al2O3 and Na2O contents, and also have high molar K2O/Al2O3, molar (K2O + Na2O)/Al2O3 and K2O/Na2O ratios. Their high abundances of incompatible trace elements such as large ion lithophile elements (LILE) and light rare earth elements (LREE) reach the extreme levels typical of lamproites. The lamproites show highly radiogenic Sr-87/Sr-86 (0. 7166-0. 7363) and unradiogenic Nd-143/Nd-144 (0. 511796-0. 511962), low Pb-206/Pb-204 (18. 459-18. 931), and elevated radiogenic Pb-207/Pb-204 (15. 6732-15. 841) and Pb-208/Pb-204 (39. 557-40. 058) ratios. On the basis of their geochemical and isotopic systematics, the lamproites in south Tibet have a distinct magma source that can be differentiated from the sources of potassic lavas in the east Lhasa and Qiangtang blocks. Their high Nb/Ta ratios (17. 10-19. 84), extremely high Th/U ratios (5. 70-13. 74) and distinctive isotope compositions are compatible with a veined mantle source consisting of partial melts of subducted Tethyan oceanic sediments and sub-continental lithospheric depleted mantle. Identification of the lamproites and the delineation of their mantle source provide new evidence relevant for models of the uplift and extension of the Tibetan plateau following the Indo-Asia collision. Metasomatism by partial melts from isotopically evolved, old sediment subducted on the young Tethyan slab is an alternative explanation for Precambrian Nd and Pb model ages. In this model, differences in isotopic composition along-strike are attributed to differences in the type of sediment being subducted, thus obviating the need for multiple metasomatic events over hundreds of million years. The distribution of lamproites, restricted within a north-south-trending graben, indicates that the initiation of east-west extension in south Tibet started at similar to 25 Ma.
WOS关键词	INDO-ASIAN COLLISION ; EAST-WEST EXTENSION ; ULTRAPOTASSIC ROCKS ; POSTCOLLISIONAL MAGMATISM ; ISOTOPIC CHARACTERISTICS ; GEODYNAMIC IMPLICATIONS ; LITHOSPHERIC MANTLE ; THERMAL EVOLUTION ; VOLCANIC-ROCKS ; CORE FORMATION
WOS研究方向	Geochemistry & Geophysics
语种	英语
出版者	OXFORD UNIV PRESS
WOS记录号	WOS:000245353800005
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/68120]
专题	中国科学院地质与地球物理研究所
通讯作者	Gao, Yongfeng
作者单位	1.Shijiazhuang Univ Econ, Dept Resources, Shijiazhuang 050031, Hebei, Peoples R China 2.Chinese Acad Sci, Inst Geol, Beijing 100037, Peoples R China 3.Laurentian Univ, Dept Earth Sci, Sudbury, ON P3E 2C6, Canada 4.Chinese Acad Geol Sci, Inst Mineral Resources, Beijing 100037, Peoples R China 5.Hebei Bur Land & Resources, Shijiazhuang 050051, Hebei, Peoples R China
推荐引用方式 GB/T 7714	Gao, Yongfeng,Hou, Zengqian,Kamber, Balz S.,et al. Lamproitic rocks from a continental collision zone: Evidence for recycling of subducted Tethyan oceanic sediments in the mantle beneath southern Tibet[J]. JOURNAL OF PETROLOGY,2007,48(4):729-752.
APA	Gao, Yongfeng,Hou, Zengqian,Kamber, Balz S.,Wei, Ruihua,Meng, Xiangjin,&Zhao, Rongsheng.(2007).Lamproitic rocks from a continental collision zone: Evidence for recycling of subducted Tethyan oceanic sediments in the mantle beneath southern Tibet.JOURNAL OF PETROLOGY,48(4),729-752.
MLA	Gao, Yongfeng,et al."Lamproitic rocks from a continental collision zone: Evidence for recycling of subducted Tethyan oceanic sediments in the mantle beneath southern Tibet".JOURNAL OF PETROLOGY 48.4(2007):729-752.