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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, Lei1,2; Liu, Xiao-Chi1; Wang, Jia-Min1; Wu, Fu-Yuan1,2
2019-10-01
Source PublicationLITHOS
ISSN0024-4937
Volume342Pages:542-556
AbstractWidespread 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.
KeywordHimalayan orogen Leucogranite Fractional crystallization Leucosome Partial melting Nyalam
DOI10.1016/j.lithos.2019.06.007
Funding OrganizationNational 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
WOS KeywordS-TYPE GRANITES ; METAPELITIC MIGMATITES ; ISOTOPIC COMPOSITIONS ; CRUSTAL ANATEXIS ; TETHYAN HIMALAYA ; FLUID-ABSENT ; SHEAR ZONE ; TURKU AREA ; CONSTRAINTS ; ZIRCON
Language英语
Funding ProjectNational 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]
Funding OrganizationNational 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
WOS Research AreaGeochemistry & Geophysics ; Mineralogy
WOS SubjectGeochemistry & Geophysics ; Mineralogy
WOS IDWOS:000477091500035
PublisherELSEVIER
Citation statistics
Document Type期刊论文
Identifierhttp://ir.iggcas.ac.cn/handle/132A11/92916
Collection岩石圈演化国家重点实验室
Corresponding AuthorLiu, Xiao-Chi
Affiliation1.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
First Author AffilicationState Key Laboratory of Lithospheric Evolution
Corresponding Author AffilicationState Key Laboratory of Lithospheric Evolution
Recommended Citation
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.
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