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Indian Ocean-MORB-type isotopic signature of Yushigou ophiolite in North Qilian Mountains and its implications

science china earth sciences 2006年第6期49卷 561-572页

作者： HOU Qingye1,2. ZHAO Zhidan1,2. ZHANG Hongfei3, ZHANG Benren3 & CHEN Yuelong2.1. state Key Laboratory of geological Processes and mineral {2., china university of geosciences, beijing 100083, china 2. school of earth science and mineral {2., china university of geosciences, beijing 100083, china 3. faculty of earth sciences, china university of geosciences, Wuhan 430074, china state Key Laboratory of geological Processes and mineral {2. China University of Geosciences Beijing China school of earth science and mineral {2. China University of Geosciences Beijing China faculty of earth sciences China University of Geosciences Wuhan China

In order to explore the disputed issue concerning the tectonic affinity ofthe ancient ocean mantle of North Qilian Mountains (NQM), geochemical and sr, Nd, Pb isotopiccompositions of pillow basalts of the Yushigou Ophiolite (YsGO) suite from NQM have been analyzedsystematically. The pillow basalts exhibit tholeiitic characteristics, with flatchondrite-normalized REE patterns ((La/Yb)_N = 0.98—1.2.). They display no Nb, Ta, Zr, Hf negativeanomalies, and show MORB features in 2.b-Zr/4-Y and Ti/100-Zr-YX3 tectonic discrimination *** results indicate that the Yushigou ophiolite is most likely to be formed in a mid-ocean ridgeor mature back-arc basin. Their isotopic data show a relatively broad and enriched ^(87)sr/^(86)sr(0.70509 — 0.70700), restricted ^(143)Nd/^(144)Nd (0.512.55-0.512.78). Pb isotopes are in the rangeof ^(2.6)Pb/^(2.4)Pb (18.054-2..562., ^(2.7)Pb/^(2.4)Pb (15.537-15.743) and ^(2.8)Pb/^(2.4)Pb(38.068-38.530). These isotopic data imply that the basalts originated from the depleted mantle(DMM), with the involvement of enriched mantle components (mainly EMII). geochemical comparisonsbetween the basalts in YsGO and the MORB-type basalts of ophiolite suites occurring in the knownancient Tethyan tectonic domain indicate that the ancient oceanic mantle represented by YsGO suiteforming in early Paleozoic in the North Qilian Moutains is very similar to the Tethyan mantle inboth trace elements and isotopic compositions. The North Qilian Mountains should be a part of theTethyan tectonic domain in early Paleozoic. This further implies that the Tethyan tectonic domaincan be deduced to early Paleozoic in the study area, which will be helpful to discussing thetectonic affinity and evolution of the North Qilian Mountains.

关键词： geochemistry, Indian Ocean-MORB-type isotopic signatures, Tethyan tectonic domain, Yushigou ophiolite, North Qilian Mountains.

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The species diversity of fusulinaceans and high-frequency sea-level changes in the Carboniferous-Permian boundary section at Xikou, Zhen'an County,shaanxi Province, china

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science china earth sciences 2006年第7期49卷 673-683页

作者： ZHANG Haijun1, WANG Xunlian2. DING Lin1, XIA Guoying3 & WANG Lei2.1. Institute of Tibetan Plateau Research, Chinese Academy of sciences, beijing 100085, china 2. {2. of earth sciences and mineral resources, china university of geosciences, beijing 100083, china 3. Tianjin Institute of geology and mineral resources, Tianjin 300170, china Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing China faculty of earth sciences and {2. resources China University of Geosciences Beijing China Tianjin Institute of geology and mineral {2. Tianjin China

The study on the interrelation between sea-level changes and biodiversity with its evolu-tion has great significance for understanding the impact of global changes on organic evolution and exploring the inherent laws of life-environment coevolution in geological history. In this paper, the stratigraphic distribution of fusulinacean fauna in the Carboniferous-Permian boundary section at Xikou, Zhen’an County, shaanxi Province, is analyzed quantitatively, and the relationship between the species diversity of fusulinaceans and relative sea-level changes is discussed. As a whole, the spe-cies numbers of fusulinacean fauna experience a rapid increase and an obvious decline in Xikou, Zhen’an County, from the Late Carboniferous to the Early Permian. There is a significant increase in species diversity around the Carboniferous-Permian boundary, which is one of the biggest bio-events of the fusulinacean fauna, and represents the radiation of Pseudoschwagerininae subfamily in the studied area. Integrated fusulinacean species diversity into sequence stratigraphic framework, de-tailed study suggests that the species diversity of the fusulinaceans is closely related to its relative stratigraphic location, and is essentially controlled by the sea-level changes, especially by the high-frequency sea-level changes. Generally, the species diversity of fusulinaceans is low, and the number of first and last appearance datum is small in the lower unit of high-frequency depositional cycle formed during the quick rise of the sea level; whereas the species diversity of fusulinaceans is high, and the number of first and last appearance datum is large in the upper unit of high-frequency cycle formed during the slow fall of the sea level. Within the third-order depositional sequence, the species diversity of the fusulinaceans at the first flooding surfaces and the maximum flooding surfaces is low, and it increases upward. The fusulinacean species diversity is low within the transgressive syst

关键词： fusulinaceans, species diversity, high-frequency cyclothem, sequence stratigraphy, sea-level changes, Carboniferous-Permian boundary, Zhen'an, shaanxi.

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Transport network and flow mechanism of shallow ore-bearing magma in Tongling ore cluster area

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science china earth sciences 2006年第4期49卷 397-407页

作者： DENG Jun1,2. WANG Qingfei1,2., HUANG Dinghua3 , WAN Li4, YANG Liqiang1,2.& GAO Bangfei1,2.1. state Key Laboratory of geological Processes and mineral {2., china university of geosciences, beijing 100083, china 2. Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education, china university of geo- sciences, beijing 100083, china 3. faculty of earth sciences, china university of geosciences, Wuhan 430074, china 4. school of Mathematics and Information science, Guangzhou university, Guangzhou 510405, china state Key Laboratory of geological Processes and mineral {2. China University of Geosciences Beijing China Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education China University of Geosciences Beijing China faculty of earth sciences China University of Geosciences Wuhan China school of Mathematics and Information science Guangzhou University Guangzhou China

Abundant studies revealed that shallow intrusions of the Yanshanian epoch resulted in the mass mineralization of the Tongling region. Various evidences showed there existed a concealed magma chamber at ?10 km depth in the middle part of this region during Yanshanian epoch, from which the ore-forming magma was generated and then transported to the superficial layer. Yet the transport network and flow mechanism of the shallow ore-bearing magma, the key problem associ- ated with ore-forming process, was relatively little focused on. Integrate analysis of structural me- chanics, statistical fractal and geological facts suggested that NE trending high-angle fold-related thrust faults and the tessellated basement ones served as the main pathways for the shallow magma’s transporting, moreover, the saddle void spaces among adjacent strata in the folds upon this fault system provided the place for magma’s emplacement. so the folds in the upper part and faults in the lower part of the upper crust constituted the fluid’s transport and emplacement network. During the deformation of geologic body with multi-layer structure, the layers in the upper part tended to fold when received the jacking stress from the lower part, while the lower one inclined to fault undergoing loads of the upper part. And the producing probability of this structure assemblage was highly in- creased in the condition, such as in the Tongling area, that the mechanic rigidity of the lower layers was stronger than that of the upper ones. For the pre-existence of fluid-conducting network, the top magma with high volatile in the magma chamber transported rapidly to the superficial layer in dyking pattern, located in the void spaces of folds, filled and reconstructed them. The sudden drop of pres- sure caused the fluid unmixing from the magma and mass ore-forming elements concentration. Pulse activity of the dyking may be the principal reason why magmatic bodies in the Tongling area were spatially-temporally con

关键词： Tongling, structural network, magma intrusion, fractal, dyke.

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Exsolution of ilmenite and Cr-Ti magnetite from olivine of garnet-wehrlite

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science china earth sciences 2005年第9期48卷 1368-1376页

作者： LIU Xiangwen1,2. JIN Zhenmin1,3, QU Jing2.& WANG Lu2.1. state Key Laboratory of geological Processes and mineral {2., china university of geosciences, Wuhan 430074, china 2. Graduate school of china university of geosciences, Wuhan 430074, china 3. faculty of {12. sciences, china university of geosciences, Wuhan 430074, china state Key Laboratory of geological Processes and mineral {2. China University of Geosciences Wuhan China Graduate school of china university of {2.sciences Wuhan China faculty of earth sciences China University of Geosciences Wuhan China

Exsolution of rod-like ilmenite (Ilm) and Cr-Ti magnetite (Mt) have been found in olivine of garnet-wehrlite from the core of Chinese Continental sciences Drilling (CCsD). Their composition, morphology, crystal structure and their topotaxies with host olivine have been studied in detail by the transmission electron microscopy (TEM) and electron probe microanaly- sis (EPMA) technique. It shows that rod-like Ilm exsolution reported in this paper has similar characteristic with that of Alpe Arami olivine, while Cr-Ti magnetite exsolution mentioned in this paper has large discrepancy with chromite exsolution in Alpe Arami olivine. These observations suggest that both of the exsolutions found in this paper should be solid solution phases in β-olivine at their first period, then experiencing decomposition of solid solution and therefore forming Ilm and Cr-Ti magnetite exsolution with the pressure decreasing. so, this garnet-wehrlite perhaps had been ever located in mantle transition zone with a minimum depth of 300 km.

关键词： garnet-wehrlite, ilmenite, magnetite, exsolution, CCsD.

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Experimental remolding on the caprock's 3D strain field of the Indosinian-Yanshanian epoch in Tongling deposit concentrating area

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science china earth sciences 2005年第7期48卷 863-874页

作者： DENG Jun1,HUANG Dinghua2.WANG Qingfei1,WAN Li1,sUN Zhongshi3,YANG Liqiang1 & GAO Bangfei1 1. state Key Laboratory of geological Processes and mineral {2.,china university of geosciences,beijing 100083,china 2. faculty of earth sciences,china university of geosciences,Wuhan 430074,china 3. Department of earth sciences,Jilin university,Changchun 130061,china state Key Laboratory of geological Processes and mineral {2. China University of Geosciences Beijing 100083 China faculty of earth sciences China University of Geosciences Wuhan 430074 China Department of earth sciences Jilin University Changchun 130061 China

Based on field observations and rheology analysis, we perform one analogue experiment and remold the 3D structural frame of Tongling deposit concentrating area firstly. Then we disassemble and dialyze the 3D structures of the model using the methods of "slicing" and "stripping". A series of sliced planes vertical to the fold hinges show similar landscapes of that in the drill hole profiles. Meanwhile, layer stripping analysis indicates that the deformation features of each layer in the model are qualitatively analogical to those obtained from field observations. Through contrasting the 3D structure between the experimental model and the field phenomena, we verify the following 3D deformation features of the caprock in this area: (1) the Tongling area mainly consists of three series of NE s-typed fold groups; (2. in the uniform stress field, the incoherent folds universally develop in different positions, along different axes as well as in different strata; (3) the faults propagate upward which are mostly inter-bedded detachment faults, while the fold amplitudes decrease while going deeper; and (4) the folds and cleavages are highly developed in the silurian system indicating that the deformation effect of the Indosin-ian-Yanshanian structural layer terminates at this layer, which suggests that the silurian system is the crucial layer for the inversion between brittle and plastic deformation domains and the underlying strata are subject to the control of another deformation system with distinct properties.

关键词： Tongling deposit concentrating area Indosinian-Yanshanian epoch 3D structural frame of the caprock analogue experiment slicing and stripping analysis structural model.

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geothermal and fluid flowing simulation of ore-forming antimony deposits in Xikuangshan

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science china earth sciences 2006年第8期49卷 862-871页

作者： YANG Ruiyan1,2. MA Dongsheng2. BAO Zhengyu3, PAN Jiayong2. CAO shuanglin2.& XIA Fei2.1. school of Mathematics and Physics, china university of {2.sciences, Wuhan 430074, china 2. state Key Laboratory for Research of mineral Deposits, Nanjing university, Nanjing 2.0093, china 3. faculty of earth sciences, china university of {2.sciences, Wuhan 430074, china school of Mathematics and Physics China University of Geosciences Wuhan China state Key Laboratory for Research of mineral Deposits Nanjing University Nanjing 210093 China faculty of earth sciences China University of Geosciences Wuhan China

The Xikuangshan Antimony Deposit located in the Mid-Hunan Basin, china, is the larg- est antimony deposit in the world. Based on the hydrogeological and geochemical data collected from four sections, Xikuangshan-Dajienao (AO), Xikuangshan-Dashengshan (BO), Xikuang- shan-Longshan (CO) and Dafengshan (DO) in the Basin, an advanced metallogenic model related to deep-cyclic meteoric water of Xikuangshan Antimony Deposit is put forward in this paper using a model of heat-gravity-driving fluid flow transportation. The simulation results show that the ore-forming fluid of the deposit mainly comes from the Dashengshan and Longshan areas where BO and CO sections are located if the overall basin keeps a constant atmospheric precipitation and infiltration rate during mineralization, and that the average transportation speed of the ore-forming fluids is about 0.2.0.4 m/a.

关键词： ore-forming fluid, numerical simulation, geothermal field, geofluid transport, Xikuangshan, antimony deposits.

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New stylophorans(Echinodermata) from the Upper Cambrian of Guangxi,south china

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science china earth sciences 2008年第2期51卷 181-186页

作者： HAN NaiRen1 & CHEN GuiYing1,2.1 Department of resources and Environmental Engineering, Guilin university of Technology, Gulin 541004,{2. 2.faculty of earth sciences,{2. university of geoscience, Wuhan 430074,{2. Department of resources and Environmental Engineering Guilin University of Technology Gulin China faculty of earth sciences China University of Geoscience Wuhan China

This paper describes for the first time the cornute stylophorans (Echinodermata) in china. The new material came from the Guole Formation of the Furongian (Late Cambrian) in the Guole area of Jingxi, Guangxi Province, south china. These new cornute specimens are preserved in situ and found along with well-preserved trilobites and brachiopods. One new species, Phyllocystis jingxiensis sp. nov., is proposed to accommodate these unusual materials. The new species is defined by the small, heart-shaped theca with the frame composed of ten narrow, smooth and thick marginal plates, three adoral plates and distinctive zygal and aulacophore. Both supracentrals and infracentrals are polygonal-outlined. The marginal plate M1' on the inferior face extends posteriorly to form zygal that possesses a broadened proximal end and the proximal portion joining with the conjunction between M4 and M5 on the inferior face. Aulacophore comprises ten segments at its proximal part and is conical at the middle part (named stylocone). Its distal portion is rather long and bears conspicuous ambulacrum grooves. Tectals are horizontally arranged on superior face and obliquely arranged on inferior face. Both cothurnopore and anal pyramid are vaguely seen on the right anterior corner and the extremity of theca's superior face.

关键词： Phyllocystis stylophora Echinodermata Cambrian Guangxi south china

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Problems of sequence stratigraphy in china

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Journal of earth science 2000年第3期19卷 10-20页

作者： Wang Hongzhen faculty of earth sciences and {2. resources, china university of geosciences, beijing 100083, china

A comprehensive study of outcrop sequence stratigraphy in china began in the early 1990s. The investigated strata range from Mesoproterozoic to Quaternary and the studied areas cover the three platforms and margins, the southern Himalayas and the East china and south china seas. Problems of general concern in the sequence stratigraphy of china are discussed. These are: the hierarchy for sequence stratigraphy, the third order sequence and eustasy, the chronostratigraphic boundaries and GssP, and the International stratigraphic Chart and the sequence chronostratigraphy of china. The average time interval of Mesosequence (2.-40 Ma) and of the sequence (2.5 Ma) is suggested and the minor sequences below the sequence are discussed. The time interval of the sequence shows no evident decrease with time, but several epochs with remarkable short intervals occur in the Phanerozoic, which may represent a planetary behavior denoting the special development stages in earth’s evolution. sea level change curves are given separately for the three platforms and the different regions. The Global stratotype section and Point (GssP) concept and practice are discussed, and a comparison between the first appearance point of biozone and the first flooding surface in the sequence is made for designation of the chronostratigraphic boundary. It is suggested that the chronostratigraphic boundaries might be set at the first flooding surface in the sequence for easy recognition. The idea of sequence chronostratigraphy is recommended, and a comparison between the International stratigraphic Chart and the sequence chronostratigraphy of china is made. The close relation between chronostratigraphy and sequence stratigraphy makes it possible for sequence stratigraphy to improve chronostratigraphic research. It is pointed out that multidisciplinary study in chronostratigraphy is necessary and should be promising and profitable.

关键词： sequence stratigraphy chronostratigraphy GssP china.

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Zircon geochronology and geochemistry of mafic xenoliths from Liaoning kimberlites:Track the early evolution of the lower crust,North{2. Craton

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science china earth sciences 2004年第11期47卷 961-972页

作者： ZHENG Jianping1,YU Chunmei1,LU Fengxiang1 & LI Huimin2.1.faculty of earth sciences,{2. university of geosciences,Wuhan 430074,{2. 2.Tianjin Institute of geology and mineral resources,Tianjin 300170,{2. faculty of earth sciences China University of Geosciences Wuhan China Tianjin Institute of geology and mineral {2. Tianjin China

Mafic xenoliths from Paleozoic Fuxian kimberlites (Liaoning Province) mainly in- clude garnet granulite, with minor pyroxene amphibolite, meta-gabbro and pyroxene syenite. The siO2.contents of the xenoliths are from 47.3 wt% to 49.9 wt%. The granulites are mainly coarse-medium grained and reasonably with well-developed granoblastic (mostly polygonal) texture, contain the assemblage of garnet + plagioclase + pyroxene + K-feldspar ±phlogopite. The mineral assemblage of the amphibolites is plagioclase + pyroxene + amphibole ±K-feldspar, with the equilibrium temperature and pressure conditions of 744—82.℃ and 0.76—0.88 GPa. The granulites are regarded as derivation from the lower crust depth (more than 2. km), below the amphibolites. Garnet granulites compositionally correspond to sub-alkalic basalt, and have wide ranges of Ni abundance (133—840 ppm), and Nb/Y (0.12.1.85), Nb/U (3.51—53.86) and Ta/U (0.38—2.48). The amphibolite and the syenite correspond to alkalic basalt. The Fuxian ma- fic xenoliths are regarded as the metamorphic product of the underplated magmas (including fractional crystallization or not) experienced the contamination with the pre-existed crustal com- ponents, and partly effected by kimberlitic magmas. The concordant ages of zircons for the gab- bro (2.10—2.80 Ma) and the near-concordant upper intercept ages of zircons for the garnet granulite and pyroxene amphibolite (2.78—2.38 Ma) indicate that they are currently known as the oldest deep-seated xenoliths from the lower crust of the North china Craton. These ages recorded the formation of the united Eastern Block of the North china Craton, That is, Neoar- chean (2.6—2.5 Ga) is an important continental crustal growth period of the North china Craton. The lower intercept age of the garnet granulite (1853 Ma) recorded an important tectonic thermal event in Paleoproterozoic. This event was probably related to collision of the East and West block, and resulted in the final assembly of the North china

关键词： mafic xenolith, petrochemistry, zircon geochronology, petrogenesis, lower crustal evolution, North china Craton.

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Criteria for defining and recognizing the various orders of sequences in outcrop sequence stratigraphy

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science china earth sciences 2004年第7期47卷 618-629页

作者： WANG Xunlian faculty of earth sciences and {2. resources, china university of geosciences, beijing 100083, china state Key Laboratory of Palaeobiology and stratigraphy, Nanjing Institute of geology and Palaeontology, Chinese Academy of sciences, Nanjing 2.0008, china faculty of earth sciences and {2. resources China University of Geosciences Beijing China state Key Laboratory of Palaeobiology and stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing China

The regional distribution in different depositional facies belts is here regarded as an important criterion for defining and recognizing the various orders of sequences. The third-order sequence is possibly global in nature, which may be discerned in different depositional facies belts in one continental margin and can be correlated over long distances, sometimes even worldwide. Commonly, correlation of subsequence (fourth-order sequence with time interval of 0.51.5 Ma) is difficult in different facies belts, although some of them may also be worldwide in distribution. A subsequence should be able to discern and correlate within at least one facies belt. The higher-order sequences, including microsequence (fifth-order sequence) and minisequence (sixth-order sequence), are regional or local in distribution. They may reflect the longer and shorter Milankovitch cycles respectively. sequence and subsequence are usually recognizable in different facies belts, while microsequence and minisequence may be distinguished only in shallow marine deposits, but not in slope and basin facies deposits. A brief discussion is made on the essential conditions for correct identification of sequences, useful methods of study, and problems meriting special attention in outcrop sequence stratigraphy.

关键词： outcrop sequence stratigraphy, facies belt, sequence, subsequence, microsequence, minisequence, meter-scale cyclothem, Milankovitch cycle.

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