Is Himalayan leucogranite a product by in situ partial melting of the Greater Himalayan Crystalline? A comparative study of leucosome and leucogranite from Nyalam, southern Tibet

doi:10.1016/j.lithos.2019.06.007

CORC > 地质与地球物理研究所 > 中国科学院地质与地球物理研究所 > 岩石圈演化国家重点实验室

	Is Himalayan leucogranite a product by in situ partial melting of the Greater Himalayan Crystalline? A comparative study of leucosome and leucogranite from Nyalam, southern Tibet
	Yang, Lei 1,2; Liu, Xiao-Chi1 ; Wang, Jia-Min 1; Wu, Fu-Yuan 1,2
刊名	LITHOS
	2019-10-01
卷号	342 页码:542-556
关键词	Himalayan orogen Leucogranite Fractional crystallization Leucosome Partial melting Nyalam
ISSN号	0024-4937
DOI	10.1016/j.lithos.2019.06.007
英文摘要	Widespread leucogranites in the Himalayan orogenic belt are thought to have originated by in situ partial melting of the Greater Himalayan Crystalline (GHC) when it underwent high-grade metamorphism during Cenozoic orogenesis. Therefore, the leucogranites and associated migmatites can be used to constrain the exhumation history of the GHC. However, the petrogenetic relationship between the GHC, leucogranites, and migmatites is not well constrained. As such, we carried out a detailed petrographic, mineralogical, geochronological, and geochemical study of leucosomes and leucogranites from the Nyalam region in southern Tibet. Monazite U-(Th)-Pb dating indicates that anatexis of the GHC occurred during the late Eocene and Miocene (40-14 Ma), whereas leucogranite emplacement occurred from 27 to 14 Ma. There are marked differences between the leucosomes in migmatites and leucogranites in terms of field geology, mineralogy, and geochemistry, suggesting different origins. The leucosomes occur mainly as pockets or are interlayered with melanosomes in stromatic metatexites. The leucosomes contain oligoclase and Fe-rich biotite, and have whole-rock compositions with high K2O contents (4.8-7.4 wt%) and K2O/Na2O ratios (1.35-2.97), positive Eu anomalies (Eu/Eu* = 0.93-2.61), and low rare metal (Li, Be, Cs, Sn, and Ta) contents. These features are consistent with an origin by muscovite dehydration melting of the GHC. However, the leucogranites intrude the GHC and occur as small plutons along the South Tibetan Detachment System. In contrast to the leucosomes, the plagioclase and biotite in the leucogranites are al-bite and siderophyllite, respectively. The leucogranites have relatively low K2O (4.3-4.7 wt%) contents and K2O/ Na2O ratios (1.04-1.24), high rare-metal contents, and marked negative Eu anomalies (Eu/Eu* = 0.47-0.70), indicating an origin by extensive fractional crystallization. We propose that the leucogranites were magmas produced in the deeper GHC during peak metamorphism, and subsequent extensive fractional crystallization occurred during long-distance, upward migration of magma along the South Tibetan Detachment System (STDS) during exhumation of the GHC. During these processes, the high-grade metamorphic rocks of the GHC were partially melted, resulting in the formation of leucosomes within migmatites. Therefore, the leucosomes and leucogranites have different origins and should be considered separately in studies of Himalayan orogenesis. (C) 2019 Published by Elsevier B.V.
资助项目	National Natural Science Foundation of China[41888101] ; National Natural Science Foundation of China[41772058] ; National Natural Science Foundation of China[41602054] ; Second comprehensive scientific investigation into Qinghai-Tibet Plateau[2019QZKK0803]
WOS关键词	S-TYPE GRANITES ; METAPELITIC MIGMATITES ; ISOTOPIC COMPOSITIONS ; CRUSTAL ANATEXIS ; TETHYAN HIMALAYA ; FLUID-ABSENT ; SHEAR ZONE ; TURKU AREA ; CONSTRAINTS ; ZIRCON
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER
WOS记录号	WOS:000477091500035
资助机构	National Natural Science Foundation of China ; National Natural Science Foundation of China ; Second comprehensive scientific investigation into Qinghai-Tibet Plateau ; Second comprehensive scientific investigation into Qinghai-Tibet Plateau ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Second comprehensive scientific investigation into Qinghai-Tibet Plateau ; Second comprehensive scientific investigation into Qinghai-Tibet Plateau ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Second comprehensive scientific investigation into Qinghai-Tibet Plateau ; Second comprehensive scientific investigation into Qinghai-Tibet Plateau ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Second comprehensive scientific investigation into Qinghai-Tibet Plateau ; Second comprehensive scientific investigation into Qinghai-Tibet Plateau
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/92916]
专题	地质与地球物理研究所_岩石圈演化国家重点实验室
通讯作者	Liu, Xiao-Chi
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 2.Univ Chinese Acad Sci, Coll Earth Sci, Beijing 100049, Peoples R China
推荐引用方式 GB/T 7714	Yang, Lei,Liu, Xiao-Chi,Wang, Jia-Min,et al. Is Himalayan leucogranite a product by in situ partial melting of the Greater Himalayan Crystalline? A comparative study of leucosome and leucogranite from Nyalam, southern Tibet[J]. LITHOS,2019,342:542-556.
APA	Yang, Lei,Liu, Xiao-Chi,Wang, Jia-Min,&Wu, Fu-Yuan.(2019).Is Himalayan leucogranite a product by in situ partial melting of the Greater Himalayan Crystalline? A comparative study of leucosome and leucogranite from Nyalam, southern Tibet.LITHOS,342,542-556.
MLA	Yang, Lei,et al."Is Himalayan leucogranite a product by in situ partial melting of the Greater Himalayan Crystalline? A comparative study of leucosome and leucogranite from Nyalam, southern Tibet".LITHOS 342(2019):542-556.