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Identification of Hercynian shoshonitic intrusive rocks in central Hainan Island and its geotectonic implications

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Science Bulletin 2006年第20期51卷 2507-2519页

作者： XIE Caifu1, 2. ZHU Jinchu1, DING Shijiang3, ZHANG Yeming2. FU Tai’an2.& LI Zhihong2.1. State Key Laboratory for mineral Deposits Research and Department of Earth Sciences, Nanjing University, Nanjing 2.0093, china {2., yichang 443003, china 3. Hainan Bureau of geology and mineral resources, Haikou 5702.6, china Department of Otolaryngology University Hospital VU P.O. Box 7057 1007 MB Amsterdam The Netherlands State Key Laboratory for mineral Deposits Research and Department of Earth Sciences Nanjing University Nanjing 210093 China

An identification has been made of some shoshonitic intrusive rocks in central Hainan Island recently. These rocks are K-rich (K2.=2.9%―5.1%, K2./Na2.=0.95―2.12., distinctly enriched in LILE and LREE, strongly depleted in Nb, Ta, and moder- ately depleted in Sr and Ti, with (87Sr/86Sr)i = 0.70859―0.7142. and ε Nd(t) = (?2.77―?7.49). They were derived from an EMⅡ-type mantle source. The enrichment process is related to metasomatism of depleted mantle caused by a great amount of fluid-melt released from oceanic crust and terri- genous sediments at great depth (eclogite facies) during the subduction of the South china plate under the Indochina-South china Sea plate in the Carbon- iferous–Early Permian. A SHRIMP U-Pb zircon dating yields a crystallization age of 2.2.7 Ma for the sho- shonitic intrusions, which is coeval with the strongly peraluminous granites found in central Hainan Island. These two kinds of rocks generally possess syn-intrusion ductile deformation structures. Thus they are considered to have been generated during the early stage (syn-thrust phase) of a post-collisional event. The primary magma of shoshonitic rocks was produced at a depth > 80 km by decompression- dehydration melting of previously enriched litho- spheric mantle wedge, phlogopite-bearing garnet peridotite, which was in turn caused by the break-off of a descendent slab and upwelling of a hot as- thenosphere. The rising of melts was accompaniedby crustal contamination and crystallization fractiona- tion (AFC). Combining with other related data, it is proposed that the southwards subduction and amal- gamation of the South china plate with the Indo- china-South china Sea plate took place at ca. 2.7- 2.8 Ma, which was a part of the convergence proc- ess of the Pangea supercontinent. The suture zone was probably located along the line of Song Ma-Beibu Gulf-north margin of the Yunkai Moun- tains-Wuyi Mountains.

关键词： SHRIMP U-Pb dating Hercynian shoshonitic intrusive rocks post-collisional event enriched mantle Hainan Island.

Hydrogen and Oxygen Isotope Fractionation Mechanism in the Hydrothermal System and Its Geologic Significance

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Acta Geologica Sinica(English Edition) 1992年第4期66卷 397-409页

作者： Chen Zhensheng Zhang Ligang yichang institute of {2. and mineral resources, Chinese Academy of Geological Sciences, yichang, Hubei Jiang Minxi yichang institute of {2. and mineral resources Chinese Academy of Geological Sciences Yichang Hubei

The geochemical behaviors of hydrogen and oxygen isotopes in the hydrothermal system and their inher-ent relationship with the water / rock exchange are discussed in this paper In addition to the temperature con-ditions, the effective W / R ratio is another factor controlling the changes in H and O isotope compositions ofthe altered rock and hydrothermal water. Besides, the application and geological significance of the water-rockexchange theory are also discussed in the light of the H and O isotope compositions and their variation charac-teristics of the mineralizing hydrothermal water and altered rocks from several mineral deposits. Finally, abrief evolutional model of H and O istotope compositions of meteoric and magmatic hydrothermal waters in ahydrothermal system is given.

关键词： hydrothermal system isotope fractionation mechanism water/rock exchnage effective W/R ratio evolutional model

Characteristics of fluid inclusion planes and dynamical mechanism of structure-fluid-ore-forming processes in Yindongpo gold deposit, Henan Province, china

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Chinese Science Bulletin 1999年第S2期44卷 150-152页

作者： WEI Changshan~1, ZHAI Yusheng~2.and GHI Sanchuan~2.1. yichang institute of {2. and mineral resources, Chinese Academy of Geoscience, yichang 443003, china 2. china University of Geosciences, Beijing 100083, china yichang institute of {2. and mineral resources Chinese Academy of Geoscience Yichang 443003 China china University of Geosciences Beijing 100083 China

THE Yindongpo gold deposit, situated in northern Tongbei County, northern Qinling orogenic belt, is alarge-scale one controlled by the Heqianzhuang anticline that plunges northwestwards and dips northeastwards. The ore-bodies locates in the carbon layers belonging to the Neoproterozoic Waitoushan *** ore-forming periods can be distinguished: the pre-Mesozoic epithermal mineralization in primary sediment with metamorphic superposition and the Mesozoic epithermal-mesothermal mineralization related totectonomagmatic activities. The principal ore-forming period can be divided into four stages. The ore bodies consist of networked and brecciated quartz veins. Gold is mainly rich in the veinlet-type quartz veinsthat formed during the diagentic-metamorphism or syn-metamorphic hydrothermal period, but a little inthe coarse veins related to later tectonomagmatic activities. The phenomenon that the fracturing degree

关键词： fluid inclusion planes dynamical mechanism structure-fluid-ore-forming processes gold deposit Yindongpo Henan.

^(2.7)Pb/^(2.6)Pb Zircon Dating of the Huangtuling Hypersthene-Garnet-Biotite Gneiss from the Dabie Mountains, Luotian County, Hubei Province, china: New Evidence for Early Precambrian Evolution

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Acta Geologica Sinica(English Edition) 1999年第1期73卷 78-83,127-128页

作者： JIAN Ping YANG Weiran and ZHANG Zichao institute of geology,CAGS,2. Baiwanzhuang Rd, Beijing 100037{2. University of Geosciences, Wuhan, Hubei 430074 yichang institute of geology and mineral resources, CAGS, yichang, Hubei 443003 CAGS Inst Geol Beijing 100037 Peoples R China china Univ Geosci Wuhan 430074 Hubei Peoples R China CAGS Yichang Inst Geol & Mineral Resources Yichang 443003 Hubei Peoples R China

The Huangtuling hypersthene-garnet-biotite gneiss at Luotian County, Hubei Provine, is a typicalgranulite-facies rock of the Dabie Group Complex in the Dabie orogenic belt. Investigations on the morphology andoccurrence of zircons and their internal structures shown in the thin sections lead to the recognition of three types ofzircons, which are in good agreement with the types identified on the basis of morphology, colour and external fea-tures from the related zircon concentrates. The observation of zircons in the rock reveals that part of type 1 zirconsshow signs of a double-layered structure. The interval part existed in the protolith prior to the granulite-facies meta-morphism. Type 2. the prismatic zircons which mainly occur in garnet and hypersthene are metamorphic minerals ofthe granulite-facies metamorphism. Type 3, the round multifaceted zircons in felsic minerals and biotite, are proba-bly attributed to a later geological event related to migmatization. The ^(2.7)Pb/^(2.6)Pb zircon dating by direct evaporationon (thermal evaporation ion mass spectrometer) yields ages ranging from 2.14 Ma to 1992.Ma. The age discrepancyamong these different zircon types is conspicuous. The yellow-brown(type 1) zircons give ages of 2.14±2. Ma to2.2.±6 Ma, the prismatic euhedral zircons (type 2., 2.56±7 Ma to 2.54±4 Ma, and the round multifaceted zircons(type 3), 1992.10 Ma. The results are geologically interpreted in consideration of the complicated behaviours of zir-cons during Precambrian geological evolution of the Dabie area. (1) If the protolith of the gneiss is a sedimentaryrock, then type 1 zircons are clastic ones and the ages 2.14±2. Ma and 2.11±2. Ma may reflect the minimum age ofthe rocks of its source region. also the first geological event in the area. Sedimentation of the protolith occurred be-tween 2.14 Ma and 2.2. Ma, probably close to 2.14 Ma. If the protolith is a volcanic rock, then the formation age ofthe supracrustal rocks of the Dabie Group Complex is

关键词： Dabie Mountains granulite facies Archaean multistage evolution zircon 2.7~Pb/2.6~Pb

Early Ordovician Sea Level Changes in South china and Their Worldwide Correlation

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Journal of Earth Science 1996年第1期15卷 54-62页

作者： Wang Xiaofeng (yichang institute of {2. and mineral resources, CAGS, yichang 443003) Li Zhiming Chen Jianqiang (Department of {2. and mineral resources, china University of Geosciences, Beijing 100083) Chen Xiaohong (yichang institute of {2. a

The sea level changes and their correlation from the latest Cambrian C. proavus zone to the Ordovician N. gracilis zone in South china are discussed on the basis of the Ordovician paleogeographic reconstruction in china. The study of sequence, biostratigraphy and ecostratigraphy suggests that at least 8 major regressive events, occurring in the following levels: basal H. simplex zone (RE1), near the base of C. intermedius zone (RE2., basal C. angulatus zone (RE3), near Mid/Upper G. quadriplicatus zone (RE4) and succeeding the first phase (RE4a) of RE4 at basal P. deltifer zone, Kiaerograptus/Brygograptus zonal boundary (RE5), end *** A. Z.(RE6), end P. originalis zone (RE7) and Early H. teretiusculus or end P. serra zone (RE8), can be recognized in the cratonic plat- form and its shelf-slope tracts of the South china plate based on sequence change or disconformity and associated breaks in biological succession. Most of them can be traced in the other plates or continents.

关键词： Ordovician sea level change sequence.

The Genetic Types of Some Granite Intrusions Associated with Tin Polymetallic Deposits in the Nanling Region

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Acta Geologica Sinica(English Edition) 1988年第3期1卷 307-324页

作者： Liu Houqun Yang Shiyi yichang institute of {2. and mineral resources, CAGS, yichang, Hubei yichang institute of {2. and mineral resources CAGS Yichang Hubei

Tin polymetallic deposits are the most important type of tin deposit in the Nanling region. Manyresearchers both at home and abroad consider this type of tin deposit to be the product of differentiation andevolution of granite magmas resulting from anatexis of continental crust and to be genetically related to thetransformation-type (S-type) granitoids. In this paper, on the basis of the geological settings, petrology, REEgeochemistry and strontium and oxygen isotopic compositions of 6 granite intrusions associaied with tinpolymetallic deposits in the Nanling region, the authors suggest that the ore-bearing granites of this type areprobably the products of differentiation and evolution of acid magmas resulting from 40-50‰ fractionalcrystallization of magmas formed by partial melting of the pre-existing intermediate-basic volcanic rocks ofmantle origin in the lower crust and a small amount of sialic material and belong to crust-mantle-derivedgranitoids (approaching I-type of B. W. Chappell and A.J.R. White, but being evidently different from theS-type granitoid related to W, Sn, Nb, Ta and REE deposits).

关键词： The Genetic Types of Some Granite Intrusions Associated with Tin Polymetallic Deposits in the Nanling Region

Genesis of Yangla Banded Skarn-Hosted Copper Deposit in Tethys Orogenic Belt of Southwestern china

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Journal of Earth Science 1999年第1期18卷 62-65页

作者： Zhan Mingguo Lu Yuanfa yichang institute of {2. and mineral resources, CAGS, yichang 443003 Dong Fangliu Department of {2. and mineral resources, china University of Geosciences, Beijing 100083 Chen Kaixu Wei Junqi yichang institute of

Yangla copper deposit is the largest banded skarn hosted copper deposit found recently in the Tethys orogenic belt of Southwestern china. On the basis of the study of distribution, petrology and mineralogy as well as major element, REE and isotope geochemistry, the authors find that the banded skarn, which hosts the deposit, was precipitated from hydrothermal solutions in the form of exhalate sediment. Therefore, the banded skarn hosted copper deposit is a Sedex type deposit, with a series of stacked, conformable lenses underlain by at least one stringer zone. The deposit, intercalated at the contact of lower clastic rock and upper carbonate rock of Gajinxueshan Group, was formed in the Carboniferous ((2.6.1±7.0) Ma), contemporary to the host Gajinxueshan Group. The interpretation of the genesis of Yangla banded skarn hosted copper deposit is of fundamental exploration significance for the discovery of Sedex type copper deposit in the region.

关键词： banded skarn metallogenic genesis Yangla copper deposit.

Hydrogen and Oxygen Isotope Study on the Water-Rock Interaction of the Yinshan (Cu-) Pb-Zn-Ag Ore Deposit, Jiangxi Province

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Acta Geologica Sinica(English Edition) 1996年第3期70卷 274-289页

作者： Zhang Ligang, Liu Jingxiu, Yu Guixiang and Chen Zhensheng yichang institute of {2. and mineral resources, CAGS, yichang, Hubei Jiang Minxi Y ichang institute of geology and {2. resources CAGS Yichang Hubei

The δ18O values of vein quartz of different stages from the Yinshan ore deposit are constant around 16‰ and the calculated δ18OH2. values attain 8‰± ; the δDH2. values of fluid inclu-sions in vein quartz are constant at about-60‰. From the surface down to 12.0 m below the δ18O values of altered rocks gradually decrease from 15‰± to 11‰± . Various water-rock inversion calculations indicate that the ore fluids were formed by the interaction between meteoric water and phyllite at 350℃ and the effective W/ R value of around 0.1. When the water-rock exchange in the upper mineralization system took place, the effective W / R value increased to 5.0 or more. As a result, an evolution and mineralization model of a buffered open system with two-stage water-rock interactions is proposed in this study.

关键词： H and O isotopes water-rock exchange buffered open system Yinshan of Jiangxi Province

Isotopic Geochronological Evidence for the Caledonian Xiongdian Eclogite in the Northwestern Dabie Mountains,china

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Acta Geologica Sinica(English Edition) 1997年第4期71卷 455-465页

作者： Jian Pingyichang institute of {2. and mineral resources. CAGS, yichang City,Hubei Province 443003Yang Weiran china University of Geosciences, Wuhan, HubeiLi Zhichang yichang institute of {2. and mineral resources, CAGS, yichang, HubeiZhou Huifang Tianjin Instutite of {2. and mineral resources, CAGS, Tianjin Zhu Xiling

A typical HP/MT (high pressure/medium temperature) eclogite from Xiongdian, northwestern Dabie Mountains, has been geochronologically studied using the single-zircon U-Pb, 40Ar-39Ar and Sm-Nd methods. Prismatic zircons occurring as inclusions within garnets define a minimum crystallization age of 399.5±1.6 Ma. 40Ar-39Ar dating on amphibole gives a plateau *** 399.2.± 4 Ma, which is interpreted as a retrogression age of amphibolite facies. This integrated study enables us to conclude that the age of high-pressure metamorphism is older than 399.5 ± 1.6 Ma, suggesting Caledonian collision between the North china and Yangtze plates. Round zircon within the aggregate of quartz and muscovite gives a concordant age of 301± 2.Ma, reflecting a later retrogression event. An age profile of post-eclogite metamorphism is documented, including amphibolite facies metamorphism at 399.2.Ma shortly after eclogitization and later retrogressive metamorphism at 301 Ma. Sm-Nd mineral isochron of garnet+omphacite gives an unreasonable age of 544 ± 2. Ma. which is quite older than that of prismatic zircon and may be attributed to isotopic disturbance by retrogression.

关键词： Caledonian collision eclogites geochronlogy Northwestern Dabie area Xiongdian Henan