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Metamorphism and Zircon Geochronological Studies of Metagabbro Vein in the Yushugou granulite-Peridotite Complex from South Tianshan,China

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Journal of Earth Science 2019年第6期30卷 1215-1229页

作者： Lu Zhang Jianjiang Zhu Bin Xia Cong Zhang Lifei Zhang Center for High Pressure Science and Technology Advanced Research Beijing 100094China Key Laboratory of Orogenic Belts and Crustal Evolution MOESchool of Earth and Space SciencesPeking UniversityBeijing 100871China Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources Institute of GeologyChinese Academy of Geological SciencesBeijing 100037China School of Earth Sciences^China University of Geosciences Wuhan 430074China College of Earth Science and Engineering Shandong University of Science and TechnologyQingdao 266590China

Yushugou granulite-peridotite complex,located at the east part of the northern margin of South Tianshan,may represent an ophiolitic slice subducted to 40–50 km depth with high-pressure granulite facies metamorphism.Although a lot of studies have been conducted on rocks in this belt,the rock association and tectonic background of the ophiolitic slice are still in dispute.A detailed study on petrology,phase equilibrium modeling and U-Pb zircon ages have been performed on the metagabbro vein in peridotite unit to constrain the tectonic evolution of the Yushugou granulite-peridotite complex.Three stages of mineral assemblage in the metagabbro were defined as stage I:Cpx^A+Opx^A+Pl^A,which represents the original minerals of the metagabbro vein;stage II:Cpx^B+Opx^B+Pl^B+Spl,which represents the mineral assemblage of granulite facies metamorphism with peak P-T conditions of 4.2–6.9 kbar and 940–1070℃;stage III is characterized by the existence of prehnite,thomsonite and amphibole in the matrix,indicating that the metagabbro vein may be influenced by fluids during retrograde metamorphism.Combined with the crosscut relationship,it can be deduced that the metagabbro vein,together with the peridotite in Yushugou granulite-peridotite complex has experienced similar high-temperature granulite facies metamorphism.The zircon chronological data shows that the protolith age of the metagabbro vein is 400.5±6.2 Ma,reflecting Devonian magmatism event and the granulite facies metamorphism occurred at^270 Ma which may be related to the post-collisional magmatism.

关键词： metagabbro vein granulite facies metamorphism P-T pseudosection U-Pb zircon dating South Tianshan

Sapphirine-Bearing Pelitic granulite from Ailaoshan Orogen,West Yunnan,China: Metamorphic Conditions and Tectonic Setting

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Journal of Earth Science 2019年第3期30卷 621-635页

作者： Cheng Wei Yuhao Zhao Luhua Zhu Xuexiang Qi Zhihui Cai Xufeng Liu Guangfei Ma Key Laboratory for Continental Dynamics of Ministry of Land and Resources Institute of GeologyChinese Academy of Geological Sciences Beijing 100037 China School of Earth and Space Sciences Peking University Beijing 100871 China Nanjing Institute of Geology and Mineral Resources Chinese Academy of Geological Sciences Nanjing 210016 China Geology Bureau for Nonferrous Metals of Guangdong Province Guangzhou 510080 China Hangzhou Mechanical Design Research Institute of Ministry of Water Resources Standard & Quality Control Research Institute of Ministry of Water Resources Hangzhou 310012 China

To reveal the petrological characteristics, metamorphic evolution histon and tectonic setting of the pelitic granulites from Ailaoshan Orogen, Uest Yunnan, China, a comprehensive study in mineral chemistry, petrogeochemistry and geochronology studies is presented in this paper. Two metamorphic stages of the granulites can be established:(1) the peak metamorphism recorded by the mineral assemblage of garnet, kyanite, K-feidspar and rutile, and the initial retrograde metamorphism shown by the mineral assemblage of garnet, sillimanite, sapphirine, spinel, K-feldspar, plagioclase and biotite;(2) the superim-posed metamorphism recorded by the mineral assemblage of biotite, muscovite, plagioclase, quartz and ilmenite. Zircon LA-ICP-MS U-Pb dating indicates that the protolith of the granulite was deposited after 337 Ma. The initial retrograde metamorphism occurred at P-T conditions of 8.6-12 kbar at 850-920℃ estimated by mineral assemblages, the low pressure limit of kyanite stability and GBPQ geothermobarometer in Indosinian (about 235 Ma), and the late superimposed metamorphism occurred at the P-T condition of 3.5-3.9 kbar at 572-576℃ estimated by GBPQ geothermobarometer since 33Ma. The first stage was related to the amalgamation of the South China and Indochina blocks during the Triassic, and the second stage was possibly related with the large scale sinistral slip-shearing since the Oligocene. It is inferred that the upper continental crust was suhducted/underthrusted to the lower continental crust (deeper than 30 km) and underwent granulite-facies metamorphism and then quickly exhumed to the middle-upper crust (10-12 km) and initial retrograde metamorphism occurred due to the collision of the Indochina and South China blocks during Indosinian, which was followed by superimposition of the second stage of metamorphism since the Oligocene.

关键词： high-pressure pelitic granulite sapphirine zircon LA-ICP-MS U-Pb dating metamorphic rocks Ailaoshan Orogen

High-Temperature Metamorphism, Anataxis and Tectonic Evolution of a Mafic granulite from the Eastern Himalayan Orogen

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Journal of Earth Science 2018年第5期29卷 1010-1025页

作者： Zeming Zhang Huixia Ding Xin Dong Zuolin Tian Dongyan Kang Hongchen Mu Shengkai Qin Yuanyuan Jiang Mengmei Li School of Earth Sciences and Resources China University of Geosciences Institute of Geology Chinese Academy of Geological Science

The Himalayan Orogen, resulting from the Tertiary collision of Indian and Asian continents, is a natural laboratory for studying metamorphism, partial melting and granite formation of collisional orogens. However, metamorphic and anatectic conditions and timescales of meta-mafic rocks in the Greater Himalayan Sequences （GHS） in the east-central Himalaya remain controversial, in this paper, we conduct a study of petrology and geochronology of mafic granulite from the Eastern Himalayan Syntaxis （EHS）. The mafic granulite with abundant leucosome bands occurs as layers within felsic granulites and is well deformed. The granulite consists of garnet, plagioclase, amphibole and quartz with minor clinopyroxene, orthopyroxene, biotite, rutile, titanite and ilmenite. The garnet has growth compositional zoning and contains abundant mineral inclusions in its core. Peak metamorphic mineral assemblage of the granulite is garnet, amphibole, plagioclase, quartz, clinopyroxene and futile, recording a high-pressure （HP） and high-temperature （HT） peak-metamorphism under conditions of 14-15.5 kbar and 780-790 ℃ in the presence of melt. The reconstructed clockwise P-T path is characterized by an early heating and burial prograde metamorphism, and late isothermal and cooling decompression retrogression. The granulite witnessed a long lasting HT metamorphism, partial melting and melt crystallization process which began at ca. 39 Ma and lasted to ca. 11 Ma. The present study shows that various high-grade rocks of the GHS in the EHS core experienced similar metamorphic conditions and P-T-t paths, indicating that they occurred as a coherent slab during the subduction and exhumation of Indian lithosphere. The significant melts generated during the prograde metamorphism of the GHS rocks not only contributed to the formation of the Himalayan leucogranite, but also resulted in the rheological weakening and ductile flow of the thickened lower crust of the Himalayan Orogen.

关键词： granulite HT metamorphism partial melting timescale collisional orogeny.

Geochronological Study of Caledonian granulite and High-Pressure Gneiss in the Dabie Mountains

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Acta Geologica Sinica(English Edition) 1998年第3期72卷 264-270页

作者： YANG Weiran JIAN Ping China University of Geosciences WuhanHubei 430074 Yichang Institute of Geology and Mineral Resources CAGSYichangHubei 443003

Using the single—zircon evaporation technique and U—Pb method, the authors have conducted an isotope geochonological study of the Huilanshan granulite and Shima garnet-bearing plagioclase gneiss (“country rocks” of the Shima eclogite) in the Dabie Mountains. The study shows that these rocks have peak metamorphic ages of 443–455 Ma, which are essentially consistent with that of the Caledonian high—ultrahigh pressure eclogites. This indicates the existence of the Caledonian collisional orogeny in the Dabie Mountains.

关键词： Dabie Mountains Caledonian granulite high-pressure gneiss isotope chronology

Discovery and Genetic Mechanism of Basic granulite in the Altay Orogenic Belt, Xinjiang, NW China

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Acta Geologica Sinica(English Edition) 2004年第1期78卷 177-185页

作者： LIZilong CHENHanlin YANGShufeng DONGChuanwan XIAOWenjiao LIJiliang YEYing WANGJian DepartmentofEarthSciences FacultyofScienceZhejiangUniversityHangzhou310027 InstituteofGeologyandGeophysics ChineseAcademyofSciencesBeijing100023

Altay granulite (AG), which represents the product of high-grade metamorphism in the lower crust, was newly found in the Wuqiagou area, Fuyun County in the Altay orogenic belt, Northwest China. It is composed mainly of hypersthene, augite, basic plagioclase, amphibole and brown biotite. Its mineral compositions of amphibole and biotite are rich in Mg/(Mg+Fe2+) and Ti. Geochemically, the AG is enriched in Mg/(Mg+Fe2+) and A12O3, and poor in CaO, with depletion of U, Th, K and Rb contents. Furthermore, geochemical data reflect that the protolith of the AG is igneous-genetic calc-alkaline basalt formed under an island arc environment. The AG has ZREE of 92.38-96.58 ppm and enriched LREE model with weak positive Eu anomaly of 1.09-1.15. In the MORB normalized spider diagram, the AG shows tri-doming pattern with a strong negative Nb anomaly and medium negative P and Ti anomalies, reflecting that the AG has tectonic relation with subduction or subduction-related materials. The P-T conditions of peak metamorphism of the AG are 750-780℃ and >0.6-0.7 GPa. Retrograde metamorphism implies that the protolith of the Altay granulite might undergo a metamorphic process along a clockwise P-T trajectory. Therefore, the formation and evolution of the AG may have a genetic association with continental collision/orogeny and the AG was taken into the Late Paleozoic meta-strata by way of tectonic emplacement.

关键词： granulite protolith and tectonic setting P-T condition genetic mechanism Altay orogenic belt Northwest China

Garnet Sm-Nd and U-Pb systems: A case study of a granulite from the European Variscan belt

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Chinese Science Bulletin 2002年第15期47卷 1284-1288页

作者： CHEN FukunInstitut fur Mineralogie, Petrologie und Geochemie, Universitat Tubingen, 72074 Tubingen, Germany Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Institut für Mineralogie Petrologie und Geochemie Universität Tübingen Tübingen Germany Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China

This study presents zircon and garnet ages of a mafic granulite from the high-grade Variscan basement of the Black Forest, Germany and discuss isotope closure temperature of garnet Sm-Nd and U-Pb systems. Zircon grains yield 207Pb/206Pb ages between -340 and -414 Ma by the U-Pb and evaporation methods. In contract, garnet dating gives Sm-Nd and Pb-Pb isochron ages of (398±3) Ma and (411±14) Ma, respectively, which are older than most of zircon ages. These data imply that most of zircons lost radiogenic Pb, probably due to metamictization or recrystallisa-tion during the granulite-facies metamorphism (-800°C) at -340 Ma. Garnet Sm-Nd and U-Pb systems preserve chronological information of pro-grade metamorphism, probably profiting from a fluid-absence metamorphic environment. These results demonstrate that garnet mineral can be a better candidate than zircon mineral to date high-grade metamorphism by the U-Pb and Sm-Nd methods in some cases.

关键词： Variscan granulite garnet Sm-Nd U-Pb.

Patterns of platinum-group elements in mantle peridotite, granulite xenoliths and basalt in Hannuoba

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Chinese Science Bulletin 1999年第18期44卷 1676-1681页

作者： CHU Xuelei, LI Xiaolin, XU Jiuhua and LIU Jianming1. The Research Center of Mineral Resources Exploration , Chinese Academy of Sciences , Beijing 100101, China 2. Institute of Geology , Chinese Academy of Sciences , Beijing 100029, China 3. Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100817 , China 4. Beijing University of Science and Engineering , Beijing 100083, China Corresponding author The Research Center of Mineral Resources Exploration Chinese Academy of Sciences Beijing China Institute of Geology Chinese Academy of Sciences Beijing China Institute of High Energy Physics Chinese Academy of Sciences Beijing China Beijing University of Science and Engineering Beijing China

Neutron activation analysis after preconcentration of nickel sulfide fire assay was used in measurement of Ru, Ph, Pd, Os, Ir, Pt (i.e. PGE elements) and Au concentrations for basalt, mantle and granulite xenoliths in Hannuoba. The chondrite- and primitive mantle-normalized PGE patterns generally exhibit flat (for Iherzolite), negative slope (for harzburgite),

关键词： mantle xenolith granulite xenolith basalt platinum-group element Hannuoba.

Zircon chronology and REE geochemistry of granulite xenolith at Hannuoba

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Chinese Science Bulletin 1998年第18期43卷 1510-1515页

作者： Qicheng Fan Ruoxin Liu Huimin Li Ni Li Jianli Sui Zhuoran Lin State Seismol Bur Inst Geol Beijing 100029 Peoples R China Minist Geol & Mineral Resources Tianjin Inst Geol & Mineral Resources Tianjin 300170 Peoples R China

The lower crustal xenolith of mafic two_pyroxene granulite (the majority) and hypersthene granulite in the Cenozoic basalt at Hannuoba have the characteristics of igneous blastic structure and granulite facies metamorphic recrystallization. Study on the zircon chronology and REE geochemistry of granulite xenolith shows that the underplating of basic magma into the lower crust during late Mesozoic led to the formation of mafic accumulate, which further through metamorphism of granulite facies formed the high_density and high_velocity crustal bottom layer at the lower crust. This suggests that the underplating of mantle magma is the important way for the vertical overgrowth of continental crust since the Phanerozoic and provides new evidence for crust_mantle interaction.

关键词： age of zircon granulite xenolith Hannuoba.

Age of granulite from Huangtuling, Dabie Mountain:Pb-Pb dating of garnet by a stepwise dissolution technique

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Chinese Science Bulletin 1999年第10期44卷 941-944页

作者： Hanwen Zhou Xianhua Li Ying Liu Zhendong You Shutian Suo Zengqiu Zhong Chinese Acad Sci Guangzhou Inst Geochem Canton 510640 Peoples R China China Univ Geosci Dept Geol Wuhan 430074 Peoples R China

A new stepwise dissolution scheme, involving acids with different properties, enables the selective recovery of radiogenic and common Pb from a mineral, and makes single-mineral Pb-Pb dating possible. Garnet from a granulite sample from Huangtuling, northern Dabie Mountain yields a Pb-Pb isochron age of (1098 ± 35) Ma, which is interpreted as the timing of peak metamorphism of granulite facies.

关键词： garnet stepwise dissolution technique Pb-Pb isochron age dating of metamorphic rocks granulite Dabie Mountain.