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

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Science china earth {2. 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 Resources, china university of geosciences, wuhan 43.074,{2. 2. Graduate School of china university of geosciences, wuhan 43.074,{2. 3. Faculty of earth sciences, china university of geosciences, wuhan 43.074,{2. 1. State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences 430074 Wuhan China 2. Graduate School of china university of geosciences 430074 Wuhan China 3. Faculty of earth sciences China University of Geosciences 430074 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.

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

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Science china earth {2. 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 Resources, china university of geosciences, Beijing 100083,{2. 2. Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education,{2. university of Geo- {4., Beijing 100083,{2. 3. Faculty of earth {4., china university of geosciences, wuhan 43.074,{2. 4. School of Mathematics and Information Science, Guangzhou university, Guangzhou 5104.5,{2. 1. State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing 100083 China 2. Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education China University of Geosciences 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

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.

Evolutionary patterns of Productida (Brachiopoda) morphology during the Permian in South china

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Science china earth {2. 2008年第11期51卷 1589-1600页

作者： ZHANG Yang1 & HE WeiHong1,2.1 Faculty of earth sciences,{2., wuhan 43.074,{4. 2.Key Laboratory of Biogeology and Environmental Geology of Ministry of Education,{2., wuhan 43.074,{4. 1. Faculty of earth sciences China University of Geosciences Wuhan 430074 China 2. Key Laboratory of Biogeology and Environmental Geology of Ministry of Education China University of Geosciences Wuhan 430074 China

The evolutionary patterns of Productida (brachiopod) morphology throughout the Permian show that while the percentage proportion of Productida (brachiopod) with strongly concentric and radial ornamentation declined from the Cisuralian to the Guadalupian, and then increased towards the Changhsingian via Wuchiapingian, the percentage proportion of Productida (brachiopod) with fine concentric and radial ornamentation distinctly increased from the Cisuralian to the Guadalupian, slightly declined towards the Wuchiapingian, and then increased towards the Changhsingian. From the Cisuralian to the Changhsingian, the percentage proportion of brachiopods with spinose ornamentation shows a persistent declining trend. The shell size generally indicates a miniaturization trend at species level during the Wuchiapingian to Changhsingian (including the transitional bed). These evolutionary patterns of brachiopod ornamentation and size are possibly related to the anoxia, food shortage, sea-level fluctuation, and change of substrate in the Permian (including the Permian-Triassic transitional interval) in South china.

关键词： brachiopod ornamentation size Permian South china

Permian carbonates of Baoshan block, Western Yunnan and their paleoclimatic implications

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Science china earth {2. 2004年第5期47卷 385-392页

作者： YAN Jiaxin1, LIANG Dingyi1 & WU Ming2.1. Faculty of earth sciences,{2., wuhan 43.074,{4. 2. College of Chemistry and Life sciences, South-Central university for Nationalities, wuhan 43.074,{4. china Univ Geosci Fac Earth Sci Wuhan 430074 Peoples R China S Cent Univ National Coll Chem & Life Sci Wuhan 430074 Peoples R China

Recently, much attention has been paid to the climatic significance of carbonates originating in shallow water. Permian carbonates of shallow shelf origin are present in the upper part of the Dingjiazhai Formation, the upper part of the Yongde Formation, and the Shazipo Formation on the Baoshan block of Western Yunnan. Their skeleton and non-skeleton grain as-sociations have been investigated in this study. The carbonates of the Dingjiazhai Formation indicate a Bryonoderm (bryozoans-echinoderm) association without non-skeleton grains. The carbonates of Yongde and Shazipo formations show Chloroforam (green algae-foraminifers) association with peloids. Oolites develop in the Shazipo Formation. Based on the comparisons of grain association with coeval carbonates formed in different paleolatitudes (i.e. various paleo-climatic zones), the carbonates of the Dingjiazhai Formation were thought to have been accu-mulated in shelf environments of warm-temperate zone, and those of the Yongde and Shazipo formations in shelf environments of warm-water.

关键词： Early Permian, carbonate, paleoclimate, Western Yunnan.

Electron microscopy study of the sakhaite from endogenous borate deposit in Hunan, china

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Science china earth {2. 2004年第3期47卷 232-238页

作者： LIU Xiangwen1,2. YANG Guangming2. ZOU Huamin3, QU Jing1 & ZHAO Wenxia4.1. Graduate School, china university of geosciences,{2., china 2. Test Center, china university of geosciences,{2., china 3. Physics and Technology College, wuhan university, wuhan 4.0072. china 4. Test Center, Zhongshan university, Guangzhou 5102.5, china china Univ Geosci Grad Sch Wuhan 430074 Peoples R China china Univ Geosci Test Ctr Wuhan 430074 Peoples R China wuhan Univ Phys & Technol Coll Wuhan 430072 Peoples R China Zhongshan Univ Test Ctr Guangzhou 510275 Peoples R China

Sakhaite specimens from an endogenous borate deposit in Hunan Province, china have been studied in detail by means of transmission electron microscopy (TEM). The selected area electron diffraction (SAED) patterns obtained with different crystal zone axes show that the crystal system is cubic, with a = 1.4.3 nm. The convergent beam electron diffraction (CBED) patterns indicate that the point group and space group of sakhaite is m3m and Fd3m, respec-tively. The space group of synthetic sakhaite determined by Chichagov (1974. is F4.32. The possible reasons why the space groups of the natural and the synthetic sakhaites are different are discussed.

关键词： sakhaite, space group, convergent beam electron diffraction (CBED).

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 {2. 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 Resources,china university of {2.,Beijing 100083,china 2. Faculty of {4. sciences,china university of {2.,wuhan 43.074,china 3. Department of {4. sciences,Jilin university,Changchun 130061,china State Key Laboratory of Geological Processes and Mineral Resources 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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Science china earth {2. 2004年第10期47卷 896-911页

作者： ZHANG Changhou1,2. WU Ganguo1,2. WANG Genhou2. ZHANG Weijie2.& SONG Honglin2.1. Key Laboratory of Lithospheric Tectonics and Lithoprobing Technology, china university of geosciences, Ministry of Education of china, Beijing 100083, china 2. School of earth {4. and Mineral Resources, china university of geosciences, Beijing 100083, china 1. Key Laboratory of Lithospheric Tectonics and Lithoprobing Technology China University of Geosciences Ministry of Education of China 100083 Beijing China 2. School of earth sciences and Mineral Resources China University of Geosciences 100083 Beijing China

The northwest trending tectonic belt in the middle part of the Mesozoic intraplate Yanshan Orogenic Belt, northeast Hebei Province, is composed of thrusts, extensional faults, strike-slip faults and syntectonic sedimentations as well. The northeastward basement-involved major thrusting deformation occurred between 174.a and 168MaBP and was followed by an intrusion of the granitic plutonic rocks. As a part of the post-thrusting extensional deformations a northwest extending volcano-sedimentation system of Late Jurassic and Early Cretaceous formed in the southwest side of the belt. These volcano-sedimentary sequences are divided into Tuchengzi Formation, Zhangjiakou Formation, Yixian Formation and Jiufotang Formation re- spectively. They are characterized by southeastward migration as a result of the increasing down-dip slip displacement along the major extensional fault toward the southeast of the belt. The provenance area of the Jiufotang Formation north to it experienced southwestward thrusting during and after its later sedimentation. The thrusting in this stage resulted in the formation of an asymmetric footwall syncline with vergence to SW in the Jiufotang Formation in the NE side of the basin. Finally a dextral strike-slip deformation occurred along the NW tectonic belt. The striking tectono-geomorphological features and present seismic activities along this belt indicate that it has been being active since Cenozoic era and is still in the active state at present. This northwest extending tectonic belt was following the same direction and location as the existing fault systems within the basement as revealed by former geological and geophysical studies. So it is reasonable to infer the Mesozoic deformation along this belt to be a result of reactivation of the basement structures in a favorable tectonic stress field. The reactivation of basement struc- tures might be taken as one of the mechanisms of intraplate deformation and orogeny.

关键词： Yanshan Orogenic Belt, northwest extending tectonic complex, thrust system, geochronology.

Carbon isotope composition of the Lower Triassic marine carbonates, Lower Yangtze Region, South china

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Science china earth {2. 2006年第3期49卷 225-241页

作者： ZUO Jingxun1,2. TONG Jinnan3, QIU Haiou4.& ZHAO Laishi3 1. Nanjing Institute of Geology and Palaeontology, Chinese Academy of sciences, Nanjing 2.0008,{2. 2. Henan Institute of Geological Survey, Zhengzhou 4.0007,{2. 3. State Key Laboratory of Geological Processes and Mineral Resources at china university of geosciences,{4.,{2. 4. Faculty of Material sciences and Chemical Engineering, china university of geosciences,{4.,{2. 1. Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing 210008 China 2. Henan Institute of Geological Survey Zhengzhou 450007 China 3. State Key Laboratory of Geological Processes and Mineral Resources at china university of geosciences Wuhan 430074 China 4. Faculty of Material sciences and Chemical Engineering China University of Geosciences Wuhan 430074 China

Studies on three Lower Triassic sections located on the shallow water platform, the deep water slope and in the deep water basin in the Lower Yangtze Region, South china, show the similar trend of carbon isotope evolution. Biostratigraphic correlations among the Lower Triassic sections on the basis of standard conodont zones indicate that three negative shifts occurred in the Griesbachian, the Smithian and the late Spathian stages respectively, and one distinctly positive shift occurred in the early Spathian stage. Trend of carbon isotope evolution of the Lower Triassic reflects some significant changes in the global carbon cycle. Moreover, δ 13C background values are intensively controlled by palaeogeographic environment. In general, δ 13C values from deep-water slope carbonates are lighter than those from carbonate platform and heavier than those from deep-water basin carbonates. The positive carbon isotope excursion may be induced by a significant amount of organic carbon burial in marine sediments and increase in primary productivity. The large negative carbon isotope excursions during the Early Triassic in Lower Yangtze Region are interpreted to relate to volcano eruptions based on tuffaceous claystone interlayers observed near the Permian-Triassic boundary, the Induan- Olenekian boundary and the Lower Triassic-Middle Triassic boundary.

关键词： Lower Triassic, carbon isotope compositions, palaeogeography, volcanic eruptions, Lower Yangtze Region.

Distributions of fatty acids in a stalagmite related to paleoclimate change at Qingjiang in Hubei,southern china

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Science china earth {2. 2005年第9期48卷 1463-1469页

作者： XIE Shucheng1,HUANG Junhua1,WANG Hongmei2.YI Yi1,HU Chaoyong1, CAI Yanjun3 & CHENG Hai4.1. Faculty of earth Science,{2. university of geosciences,{4. 43.074,{2. 2. School of Environmental Studies,{2. university of geosciences,{4. 43.074,{2. 3. SKLLQG,Institute of earth Environment,Chinese Academy of {14.,Xi’an 710075,{2. 4. Department of Geology and Geophysics,university of Minnesota,MN554.5,USA 1. Faculty of earth Science China University of Geosciences 430074 Wuhan China 2. School of Environmental Studies China University of Geosciences 430074 Wuhan China 3. SKLLQG Institute of Earth Environment Chinese Academy of Sciences 710075 Xi’an China 4. Department of Geology and Geophysics University of Minnesota 55455 MN USA

Fatty acids extracted from a subtropical stalagmite at Qingjiang in Southern china’s Hubei Province were analysed using gas chromatography-mass spectrometry. These n-alkanoic acids range from C14.to C2. in carbon number, maximizing at C16, with a second dominance at C2.. In contrast to the stalagmite analysed, the overlying soils are characterized by the dominance of heavy-molecular-weight homologues (>C2.). The n-fatty acids in the stalagmite were proposed to be contributed by both the soil ecosystems and the microbes harboring in the percolating water and the cave. The ratios of unsaturated to saturated n-fatty acids (C16:1i/C16:0, C18:1/C18:0) appear to show trends comparable with the oxygen isotope records of the stalagmite carbonate, with enhanced values associated with the cold episode such as Heinrich event 1. This paleoclimate-dependent record of the n-fatty acids might reflect microbial changes in physiology and activity in response to the temperature. This record shows somewhat difference from the previous paleoclimate signal extracted from n-alkanols and n-alkan-2.ones of the same stalagmite. The acid record fails to document the well-known Younger Dryas event which was effectively shown by the latter two biomarkers derived from soil ecosystems. This discrepancy might result from the changing biogeochemical impact on different lipid fractions as well as the varied organism populations in different ecosystems.

关键词： biomarker, ecosystem, microbe, speleothem, paleoclimate, Quaternary.