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Evolution of serpentinite from seafloor hydration to subduction zone metamorphism: Petrology and geochemistry of serpentinite from the ultrahigh pressure North Qaidam orogen in northern Tibet
Zhang, Long1; Sun, Wei-dong2,3,4; Chen, Ren-Xu5
2019-11-15
Source PublicationLITHOS
ISSN0024-4937
Volume346Pages:19
Corresponding AuthorZhang, Long(zhanglong@gig.ac.cn)
AbstractSerpentinite from the North Qaidam ultrahigh pressure metamorphic belt in northern Tibet is studied to provide insight into petro-geochemical evolution of serpentinite from seafloor hydration to subduction zone metamorphism. The North Qaidam serpentinite can be divided into undeformed lizardite serpentinite that was not severely overprinted during subduction and deformed antigorite serpentinite that was well recrystallized during subduction. Petrological and geochemical analyses demonstrate that the serpentinite was originally melt percolated refractory abyssal harzburgite. Considering the local geodynamic setting, it is inferred that the serpentinite probably originated from the oceanic lithosphere that subducted before continental subduction. Relatively uniform low delta O-18 (4.0 parts per thousand-4.5 parts per thousand.) of the antigorite serpentinite indicates high temperature hydrothermal alteration of protolith harzburgite by seawater. In contrast, much lower delta O-18 (0.6 parts per thousand-2.7 parts per thousand.) of the lizardite serpentinite is ascribed to exchange with meteoric water at the Earth's surface. Relict serpentinization textures are well preserved in the lizardite serpentinite, with reactions of olivine to lizardite and magnetite, pyroxenes to talc, tremolite, and lizardite, and spinet to chromite and chlorite. The replacement of lizardite by antigorite during subduction mostly initiates along grain boundaries and interconnecting veinlets, implying fluid-assisted transformation of lizardite into antigorite. Partial decomposition of antigorite produces magnesian secondary olivine in the antigorite serpentinite, while direct breakdown of metastable lizardite generates ferroan secondary olivine in the lizardite serpentinite. The serpentinite is enriched in fluid-mobile elements, with U primarily accumulated during seafloor alteration and alkalis notably introduced by sedimentary fluids at bending faults or in accretionary wedge. Infiltration by fluids equilibrated with sediments is also supported by highly elevated Sr-87/Sr-86 of the serpentinite. Moreover, Sr-87/Sr-86 of the antigorite serpentinite (0.710649-0.713996) is higher than that of the lizardite serpentinite (0.707184-0.708502), which implies more intense interaction of sedimentary fluids with the former than the latter. However, the lizardite serpentinite contains more alkalis and less U than the antigorite serpentinite, which indicates that large proportions of alkalis were lost during partial dehydration of serpentinite, while U was not released. (C) 2019 Elsevier B.V. All rights reserved.
KeywordSerpentinite Lizardite Antigorite Subduction Fluid-mobile elements North Qaidam
DOI10.1016/j.lithos.2019.105158
Indexed BySCI
Language英语
Funding ProjectNational Key R&D Program of China[2016YFC0600408] ; Strategic Priority Research Program of the Chinese Academy of Sciences[XDB18000000] ; Natural Science Foundation of China[41703029] ; China Postdoctoral Science Foundation[2016LH00023]
WOS Research AreaGeochemistry & Geophysics ; Mineralogy
WOS SubjectGeochemistry & Geophysics ; Mineralogy
WOS IDWOS:000488335600016
PublisherELSEVIER
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Document Type期刊论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/163293
Collection深海极端环境与生命过程研究中心
Corresponding AuthorZhang, Long
Affiliation1.Chinese Acad Sci, Guangzhou Inst Geochem, CAS Key Lab Mineral & Metallogeny, Guangzhou 510640, Guangdong, Peoples R China
2.Chinese Acad Sci, Ctr Deep Sea Res, Inst Oceanol, Qingdao 266071, Shandong, Peoples R China
3.Qingdao Natl Lab Marine Sci & Technol, Lab Marine Mineral Resources, Qingdao 266237, Shandong, Peoples R China
4.Chinese Acad Sci, CAS Ctr Excellence Tibetan Plateau Earth Sci, Beijing 100101, Peoples R China
5.Univ Sci & Technol China, Sch Earth & Space Sci, CAS Key Lab Crust Mantle Mat & Environm, Hefei 230026, Anhui, Peoples R China
Recommended Citation
GB/T 7714
Zhang, Long,Sun, Wei-dong,Chen, Ren-Xu. Evolution of serpentinite from seafloor hydration to subduction zone metamorphism: Petrology and geochemistry of serpentinite from the ultrahigh pressure North Qaidam orogen in northern Tibet[J]. LITHOS,2019,346:19.
APA Zhang, Long,Sun, Wei-dong,&Chen, Ren-Xu.(2019).Evolution of serpentinite from seafloor hydration to subduction zone metamorphism: Petrology and geochemistry of serpentinite from the ultrahigh pressure North Qaidam orogen in northern Tibet.LITHOS,346,19.
MLA Zhang, Long,et al."Evolution of serpentinite from seafloor hydration to subduction zone metamorphism: Petrology and geochemistry of serpentinite from the ultrahigh pressure North Qaidam orogen in northern Tibet".LITHOS 346(2019):19.
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