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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 4.3003, china 3. Hainan Bureau of geology and mineral resources, Haikou 5702.6, china State Key Laboratory for mineral Deposits Research and Department of Earth Sciences Nanjing University Nanjing China yichang institute of {2. and mineral resources Yichang China Hainan Bureau of geology and mineral {2. Haikou 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

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

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 4.3003, 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.

Aoyitake plagiogranite in western Tarim Block, NW china: Age, geochemistry, petrogenesis and its tectonic implications

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Science china Earth Sciences 2006年第11期49卷 1121-1134页

作者： ZHANG Chuanlin1,2. YU Haifeng3, YE Haimin2. ZHAO Yu2.& ZHANG Dongsheng4 1. Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, china 2. Nanjing institute of geology and mineral resources, Nanjing 2.0016, china 3. Tianjin institute of geology and mineral resources, Tianjin 300170, china 4. The 2.d Regional Geological Investigation Party, Xinjiang Bureau of geology and mineral resources, Changji 831100, china Key Laboratory of Isotope Geochronology and Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou China Nanjing institute of geology and {2. resources Nanjing China Tianjin institute of geology and {2. resources Tianjin China The 2.d Regional Geological Investigation Party Xinjiang Bureau of Geology and Mineral Resources Changji China

SHRIMPP U-Pb zircon age and geochemical and Nd isotopic data are reported for the Aoyitake plagiogranite in western Tarim Block, NW china. The plagiogranite intruded the Middle Pro- terozoic and Lower Carboniferous with an exposure area of ca. 60 km2.and crystallized at 330.7±4.8 Ma. Rock types mainly include tonalite, trondhjemite and minor amounts of diorite and quartz-diorite. Feldspars in the rocks are dominated by oligoclase-andesine, and minor perthite observed locally. The granites are sodic with Na/K ratios (molar) between 4 and 87. Total REE (50-2.0 ppm) show a clear positive correlation with SiO2. There is no LRRE/HREE fractionation (LaN/YbN=0.5-1.5), me- dium negative Eu anomalies (δ Eu=0.3-0.6), high Y content and low Sr/Y ratio (~1.0). These granites exhibit relatively juvenile Nd T2.M model ages of 470 to 580 Ma and positive εNd(331 Ma) values of 6.2. to 7.65. The aforementioned characteristics are similar to those of ocean island or ocean ridge plagiogranites. However, the regional geology, especially its scale, precludes that the plagiogranite pluton was derived directly from fractionational crystallization of mantle-derived basaltic magma. We interpreted that the primary magma of the pluton might be tonalitic in composition generated by ca. 50% partial melting of the juvenile basaltic crust. The primary magma experienced intensive frac- tionational crystallization, and intruded into the middle to upper crusts to form the granite pluton. In combination with the previous regional geological data, it is concluded that the plagiogranite pluton was emplaced within the Tarim Block in respond to the Carboniferous continental rifting along the Tianshan orogenic belt.

关键词： western Tarim, Aoyitake plagiogranite, age, geochemistry, tectonic implications.

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

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 4.3003) 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.

^(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 4.3003 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

Discovery of seismites in Upper Sinian stratiform lead-zinc deposits in Dadu River valley, Sichuan, china: Implication for ore genesis

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Science china Earth Sciences 2006年第11期49卷 1135-1146页

作者： LIN Fangcheng1,2.& PAN Guitang2.1. Geoscience College, Chengdu University of Technology, Chengdu 610059, china 2. Chengdu institute of {2. and mineral resources, Chengdu 610082. china Geoscience College Chengdu University of Technology Chengdu China Chengdu institute of geology and {2. resources Chengdu China

A number of lead-zinc sulphide deposits have been discovered in recent years in dolo- mitic rocks of the Upper Sinian Dengying Formation in the Dadu River valley region, Sichuan Province, china. The lead-zinc mineralization is closely associated with a black siliceous exhalite that has been traced over 50 km of strike. This makes Dadu River valley the most extensive stratiform non-ferrous sulphide horizon having been discovered to date in china. In a previous study by the first author (LIN), these deposits were recognised as belonging to the broad spectrum of lead-zinc sedimentary exhala- tive (SEDEX) deposits. In this paper, seismites and seismogenetic structures occurring in close association with the Dadu River valley mineralized zone are described. The close spatial and temporal relationship between the seismites and mineralization provides strong evidence for the hypothesis that the lead-zinc SEDEX deposits formed in direct response to earthquake activities around the Sinian-Cambrian boundary. The earthquakes are postulated to be an effective dynamic mechanism for triggering the upward migration of deep circulating ore fluids along synsedimentary growth faults and their exhalation onto the sea-floor to form the extensive deposits of stratiform lead-zinc sulphide ore.

关键词： seismites, earthquake, lead-zinc deposit, hydrothermal exhalation, Upper Sinian Dengying Age.