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    20 January 2005, Volume 19 Issue 1
    Engineering Geology and Environmental Geology
    A Pilot Study on Miocene through Holocene Sediments  from the Continental Slope of the South China Sea in Correlation with Possible Distribution of Gas Hydrates
    SU Xin, CHEN Fang, YU Xing-he, HUANG Yong-yang
    2005, 19(1):  1-13. 
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    A pilot study on Miocene through Holocene sediments throughout the continental slope of the South China Sea was carried out for evaluating possible sediment regions and layers which might be suitable for distribution of gas hydrates. Among the Miocene through Holocene sediment sequences, the highest sedimentation rates were seen from the Holocene sediments, the second record occured during the Pleistocene. This result suggests Pleistocene and Holocene sediments might be  better host for gas hydrates than sediments formed during other periods in the South China Sea.Four areas (Dongsha area, Xisha Trough, Zhongjiannan area and Nansha area) with high sedimentation rates were recognized, especially sediments from the first three areas are rich of organic carbon and contain a number of autogenetic minerals associated with gas hydrates in sediments.These sediment records imply that Dongsha area, Xisha Trough and Zhongjiannan area are of possible importance for exploration of gas hydrates.

    Stable Isotopes of Carbon and Sulfur of Cap Dolomite in the Three Gorges and its Mechanism Discussion
    WANG Jia sheng, GAN Hua yang, WEI Qing, HU Gao wei,GE Qian
    2005, 19(1):  14-20. 
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    Cap dolomite, overlying global later Neoproterozoic glacial depositions, occurs worldwide with significant stable carbon isotopic negative excursion caused most likely by the methane. Based on the study of rock textures and structures, and stable isotopes of dolomite and S isotope of barite interlayers within the cap dolomite outcropped in the Miaohe area in the Three Gorges, it is testified that the stable isotopes show a strong negative excursion, and the isotopes of sulfur show a significant positive excursion, which is similar to the reported data of authigenic barites formed in a modern seafloor gas hydrate environment. Therefore, it can be concluded that the cap dolomite was most likely formed in a special environment under which a huge gas hydrate dissociated with the breakup of “Snow Earth” in later Neoproterozoic. All of above analyses would be helpful to identify the proxies of paleo-gas hydrate deposition in some distinctive stratigraphic sections and to evaluate the global environment effect caused by gas hydrate in earth history.

    A Favorable Reservoir for Gas Hydrate Found in ODP Leg 204: Turbidite
    GONG Jian ming, ZHANG Li, CHEN Jian wen, Young Joo LEE
    2005, 19(1):  21-25. 
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    Methods of rock-mineral identification, scanning electron microscopy and energy spectrum are used to analyze 115 sediment samples from 10 drilling holes at four sites of ODP Leg 204 in order to make clear the relation between lithology and gas hydrate distribution. We find that the samples are nearly similar to each other in mineral compositions, mainly consisting of clay with minor terrestrial clasts dominated by quartz. The samples are rich in diatom and microfossils (such as foraminifers) and take the forms of diatomaceous clay, foraminiferal diatomaceous clay or tuffaceous and siliceous organic clay. Quartz clasts are mostly angular, and small both in grain size and quantity. The samples show lenticular, crumb and whirl-lamination structures, and mottled texture typical of chaotic accumulation, suggesting deep-sea or semi-pelagic turbidite or interbeds. Since drilling-proved gas hydrate samples are distributed in the turbidite, such sediments are considered as a favorable reservoir for gas hydrate of ODP Leg 204.

    Characteristics of Cold Seep Carbonates and Microbial Processes in Gas Seep System
    FENG Dong,CHEN Duo fu,SU Zheng,LIU Qian
    2005, 19(1):  26-32. 
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    Gas seep system is a common phenomenon on the seafloor in the continental shelf and slope. Venting gas is converted partially into CO2 and H2S by methane oxidizing archaea and sulfate reducing bacteria in gas seep sites,inducing  seep carbonates precipitation.The most common minerals in seep carbonates are microcrystalline calcite, microcrystalline aragonite and dolomite, and pyrite as well. Cold seep carbonates usually occur as chermoherm, nodule, chimney, hardground, cement and fine vein.Pyrite rim carbonate nodules, corrosion surfaces, inverted stromatactoid cavities, clotted fabrics,and stromatolitic are the most common sedimentary fabrics in seep carbonates. Gas seep carbonates generally are typified by low δ13C values, as they inherit the stable isotope signature from their carbon source, 13C-depleted methane.Due to the enrichment of 18O in gas hydrates, anomalously positive δ18O values in seep carbonates could argue in favour of gas hydrate destabilization at gas seep sites.The pyrite enclosed in the seep carbonates generally shows low 34S values.The 13C depleted-lipid biomarkers in cold seep carbonates are believed to reflect in-situ anabolic activity of methane oxidizing archaea and sulfate reducing bacteria

    Studies of Seismic Characteristics about Gas hydrate:A Case Study of Line HD152 in the South China Sea
    LIU Xue-wei,LI Min-feng,ZHANG Yu-wen,ZHANG Guang-xue,WU Neng-you
    2005, 19(1):  33-38. 
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    Bottom simulating reflector(BSR) and amplitude blanking zone with high velocity above BSR are the indicators of hydrate. It is difficult to recognize hydrate when BSR isn‘t in existence or amplitude blanking is not obvious because of high hydrate concentration. A useful way of recognizing hydrate is presented to identify the seismic characteriscs of hydrate zone:the high velocity zone of paralleling bottom in the low velocity background is the indicator of hydrate zone,the Poisson's ratio of hydrate zone is lower,and sections of P-wave velocity and S-wave velocity can be used  to detect free gas. A case study of line HD152 in the South China Sea is given.

    Geochemical Anomalies and Their Implication from Site 14, the Xisha Trough, the South China Sea
    ZHU You-hai, RAO Zhu, LIU Jian, LIU Ya-ling, BAI Rui-mei
    2005, 19(1):  39-44. 
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    Piston Site 14 is located in the central part of the Xisha Trough, northern slope of the South China Sea, whose geological background, gas source, temperature and pressure are preferential for gas hydrate, and some bottom simulation reflectors (BSRs) have been found. The thickness of sulfate reduction zone is about 25 meters, which indicates that gas hydrate perhaps occurs in the deeper part. A series of geochemical anomalies, including higher salinity from interstitial water, higher hydrocarbon gas concentrations and higher thermoluminescence values from sediments, have been detected at interval of 4-5 meters below sea floor at Site 14. The pore fluids with higher salinity and higher hydrocarbon, which related to gas hydrate, probably migrated into Site 14 along faults.

    Chlorine and Sulfate Concentrations in Pore Waters from Marine Sediments in the North Margin of the South China Sea and Their Implications for
     Gas Hydrate Exploration
    JIANG Shao-yong,YANG Tao,XUE Zi-chen,YANG Jing-hong,LING Hong-fei,WU Neng-you
    2005, 19(1):  45-54. 
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    This paper reports Cl- and SO42- anion concentrations in pore waters from marine sediments in the north margin of the South China Sea. Our results show that several sites in the north margin of the South China Sea display high chlorinity in pore waters. It is suggested that the salt exclusion effect during hydrate formation will cause a salinity increase of pore waters in the hydrate roof zone and shallow subseafloor sediments due to fluid diffusion. Therefore those sites with elevated chlorinity in the South China Sea deserve a further examination for gas hydrate occurrence.Analysis of sulfate concentrations in pore waters reveals a steep sulfate gradient decrease with depths, and the calculated SMI values are around 10 m, which is similar to the SMI values of those well-known gas hydrate occurrences as revealed by ODP Leg 164 and ODP Leg 204 drilling samples. The data suggest that those sites hold a great potential for gas hydrate presence at depths and warranty a further detailed exploration.

    Anomaly of Ammonia and Phosphate Concentration in Pore Waters: A Potential Geochemical Indicator for Prospecting Marine Gas Hydrate
    YANG Tao, JIANG Shao-yong,YANG Jing-hong,GE Lu,LING Hong-fei,
    2005, 19(1):  55-60. 
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    Geochemical methods have been widely used in prospecting and studying marine gas hydrate. Concentration anomalies of cations, anions, and isotopes in pore waters are useful tools to indicate the existence of gas hydrate. In particular, anomalies of Cl- concentration and oxygen isotopes, and SO42- gradients in pore water have been proved to become sensitive tracers for gas hydrate. In this study, we compared the variations of ammonia and phosphate concentrations in pore water of shallow marine sediments with depths, and found that in the gas hydrate occurrence area the pore water show significantly higher ammonia and phosphate concentrations. We also found an increasing trend of phosphate concentrations in pore waters with depths, which match the SMI curve of SO42- gradients.Therefore, we suggest that the anomalies of ammonia and phosphate concentrations in pore water may be used as a new geochemical tracer to prospect marine gas hydrate. We further discussed the possible mechanisms that cause the anomaly of ammonia and phosphate concentrations in pore water, and developed a simple and useful method to analyze concentrations of these ions in pore water and seawater.

    Foundation of Geochemical Prospecting Method Applying to Gas Hydrate Prospecting
    NIU Bin-hua,SUN Chun-yan,SU Xin,ZHAO Ke-bin,WU Neng-you,LI Jia,WANG Hong-yu
    2005, 19(1):  61-66. 
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    It is always concerned that whether the geochemical prospecting can be applied to the study of the solid form of the hydrate medium deposited in porous sedimentary stratum. This study discussed the application of geochemical prospecting from 3 aspects: (1) the fact of hydrocarbon microseepage provided by the geology and seismic exploration of hydrate,(2) the hydrate geochemical prospecting theory, the Xisha Trough geochemical prospecting and the geochemical analysis results of ODP leg 204 hydrate drilling samples,and (3) the geochemical practice in the  researching zone of the South China Sea. The results show that the geochemical prospecting can provide the favorable evidences of hydrate existence from the distribution of trace elements of the seafloor sediments.

    Estimation of the  Heat  Flow in the  Northern of the South China Sea Based on the  Seismic Data of Gas Hydrate
    WANG Hong-bin,LIANG Jin,GONG Yue-hua,HUANG Yong-yang,LIU Xue-wei,SHA Zhi-bin
    2005, 19(1):  67-73. 
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    Gas hydrates are ice-like crystalline substances composed of cages of water molecules that host low molecular weight gases mainly methane. Bottom simulating reflector (BSR) in seismic profile is an important seismic indicator for existence of gas hydrates.Because gas hydrates which have different component have relatively stable relationships of temperature and pressure respectively, pressure, temperature and even heat flow in gas hydrate stability zone can be estimated based on the data of existence of gas hydrates consequently. Using the calculating method mentioned above, typical seismic profiles in the northern of the South China Sea, where BSR can be recognized obviously, were chosen to calculate these geothermal data. The contrast between the calculated values and the measured values show that the calculated error can be limited in 12%.To a certain extent,estimation of the heat flow from seismic data of gas hydrate can provide  reliable data of heat flow for academic research; Furthermore, the data of heat flow and the experiential formula which were calibrated by measured values of heat flow can be used to predict the depth of BSR and the thickness of gas hydrate stability zone.

    Brightness Temperature Anomalies in Satellite-based Thermal Infrared Remote Sensing along the Offshore China Seas
    LU Zhen-quan,WU Bi-hao,QIANG Zu-ji,DU Le-tian
    2005, 19(1):  74-82. 
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    Based on observations of geo-stationary meteorological satellite data, lots of brightness temperature anomalies on the satellite-based thermal infrared remotely sensed images are found along the offshore China seas. After analyzing the brightness temperature anomalous features, and relating these anomalies to the conventional oil & gas fields and non-conventional potential gas hydrate occurrences, the mechanism of the anomaly is discussed. According to these anomalous implications, some possible areas for gas hydrates are pointed out,such as the Xisha Trough, the Dongsha island slope, the marginal Bijianan basin, the North Luzon Trench, the Nansha Trough, the Middle-south to Southwest Okinawa Trough etc.

    Coupled Relationship among Hydrate Structure,Hydration Number,and Raman Spectrum
    LEI Huai-yan1,2,GUAN Bao-cong1,LIU Jian-hui1,LI Zhen1
    2005, 19(1):  83-88. 
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    To discuss the affects of the different gas compositions and environment media on the forming of the different complicated clathrate hydrates with the different structure types,and hydration numbers, this study analyzed the crystal filling process of the hydrate, the crystal construction type,and the dynamics characteristics in the singleness system(CH4, CO2, and C3H8,respectively)and in the duality system(CH4+CO2, CH4+C3H8, and CH4+N2,respectively), and proceeded to analyse the results using Raman spectra. The results show that the methane fills the small cavities of 512 and the large cavities of 51262 forming structure Ⅰ clathrate hydrate(SⅠ),CO2 and C3H8 only occupy the large cavities of 51264 forming structure Ⅱ clathrate hydrate(SⅡ) in the singleness system,and that in the duality system the small cavities are only filled by CH4,neither  CO2 nor N2 and C3H8 is found. Applying the deconvoluting v1 symmetric bands to measure the relative occupancy factors of CH4 in the large cavities and in the small cavities of SⅠ, and according to the area ratio (corresponding to the small cavities and to the large cavities) of the bands, and computing the cavity occupancy factors and the coupling hydration numbers of methane hydrate under a few equilibrium terms,it is shown that the size of the gas molecule not only affects the appearance and the type of the  filling cavities , but also do the structure type and the hydration number of hydrates.

    Recent Advance in Study of Methane Hydrate Stability in Porous Media
    LU Xian-cai, YANG Tao,LIU Xian-dong,JIANG Shao-yong,WU Neng-you
    2005, 19(1):  89-95. 
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    It is proved by the long-term exploration that natural gas hydrate generally occurs within fine-grained sediments, and its stability is controlled by a number of physical, chemical and geological factors, such as temperature, pressure, pore water composition, and so on. Recent experimental studies have shown that the stability of gas hydrate in pore space with various pore structures is distinguished evidently from that of bulk one. Pore structures of host sediments significantly affect the formation and dissociation of gas hydrate, as well as wettability of pore surface. We summarize the latest experiments reported in literatures and discuss the possible influence mechanism of pore structure and wettability of inner surfaces on the stability of gas hydrates confined in pores. It is proposed that establishing an integrated thermodynamics model of methane hydrates in pore spaces with various radii, and investigating the pore structure and surface properties of hydrate-bearing sediments would advance the prediction, exploration and evaluation of gas hydrate resources. At the  same time, it is of importance for methane storage and transportation.

    Experimental Study on Elemental Geochemical Anomaly during the Formation of Marine Gas Hydrates
    LIU Chang ling ,CHEN Min , YE Yu guang
    2005, 19(1):  96-100. 
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    The elemental geochemical anomaly of pore water in marine sediments during the formation of gas hydrate is a significant indication for marine gas hydrates in the deep sea floor. Based on the experimental apparatus made by ourselves,we simulate the formation process of marine gas hydrates in laboratory, and study the variations of ionic concentrations in seawater preliminarily. The results show that the effects of formation of gas hydrate on the variations of ionic concentrations are not alike in different experimental conditions. The higher the original pressure, the larger the gas consumption, and then higher purity and larger amount hydrates are formed, resulting in stronger salt-exclusion efficiency. Therefore, the ionic concentrations are higher in seawater solution, while lower in the hydrates responding to the original pressure.

    Discussion of the Calculation Methods and Selection of Parameters of the Gas Hydrate Stability Zone
    WANG Shu hong,SONG Hai bin,YAN Wen
    2005, 19(1):  101-107. 
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    The study of the gas hydrate stability zone has great significance in comprehension of the distribution features and the resource assessment of gas hydrates.Many scholars have calculated the thickness of the stability zone by different methods, but there are some big differences among these methods, especially in the selection of parameters. The authors simply evaluate several methods and the selection of parameters for the calculation of the gas hydrate stability zone. The results show that we must consider pore-water pressure, water-column pressure and atmospheric pressure when we select the pressure formula. The second-order polynomial of pressure variation with different latitudes considering atmospheric pressure is best. The obtained equation by experiment is only used to predicting pure methane of pure water or seawater of 33.5‰ salinity. We can calculate the temperature-pressure condition of stability zone with different salinities and gas compositions by the theory of thermodynamics. The phase equilibrium plot is most simple, but its error is great. The calculated thickness of stability zone by the four-order polynomial using the experiment and thermodynamics data is close to practice. The predicted limit of the stability zone by different methods is not always consistent with actual limit of hydrate sediment.

    Sensitivity Analysis in Numerical Simulation of Natural Gas Hydrate Production
    LI Shu-xia,CHEN Yue-ming,DU Qing-jun
    2005, 19(1):  108-112. 
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    Natural gas hydrate is a newly potentially non-conventional energy resource. How to exploit it is a big problem. A one-dimension,and three-phase(gas, water, and hydrate)model is used to simulate the process of gas production from core samples containing methane hydrate by means of depressurization. Comparison between the simulation results and those of Yousif''s is carried out. In the study, factors such as the permeability,initial saturation of gas hydrates, production pressure, and temperature are taken into account.The results indicate that higher permeability, lower initial hydrate saturation, and smaller production pressure will result in faster decomposition speed of gas hydrates.

    Application of Ultrasonic Detecting Technology in the Experimental Study of Gas Hydrate
    ZHANG Jian, YE Yu-guang, DIAO Shao-bo, LIU Chang-ling
    2005, 19(1):  113-118. 
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    To understand the acoustic characteristics of gas hydrates in different media, the ultrasonic detecting technology is applied to the experimental study of gas hydrates in the pure water,the unsolidified sediment, and the core sample,respectively. The P-wave velocity is positively correlated with temperature linearly in the pure water, it means that the change of P-wave velocity is mostly caused by  temperature but unobviously by the cotton-like gas hydrate formed in the water. In the long time experiment in the pure water, unsolidified sediments, and methane system, the change of P-wave velocity and characteristic frequency sensitively indicated the formation and dissociation of gas hydrate in the experimental system. The velocity of P wave and S wave, along with the amplitude of P wave, increased when gas hydrate formed in the pore water of the core sample. It is concluded that the velocity of P wave and S wave increase when the porosity of sample decreases, while the decay of the P-wave amplitude decreases. All the experimental results reveal that ultrasonic detecting technology is effective when it is applied to the experimental study of gas hydrate.

    Transgressive-Regressive Sequences of the Upper Paleozoic at the Wudang Section in Guiyang
    Mao Jia ren
    2005, 19(1):  119-126. 
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    Located at the oldland margin from the Devonian to the Carboniferous, the Devonian System at the Wudang section includes the Mangshan Group clastic rocks and the Gaopochang Formation dolomites, and can be grouped into 5 thirdorder sequences.The Carboniferous System to the Permian Chuanshanian Series includes the Xiangbai, the Jiusi, the Shangsi, the Baizuo, the Huanglong, the Maping and the Liangshang Formation,which can be divided into 5 thirdorder sequences. The Xiangbai Formation and the Liangshan Formation  are constituted by coalmeasures, the other formations are marked by carbonates. Compared with the coeval strata in the southern part of Guizhou and the Guangxi area that are characteristic of the integrity records of strata (the Devonian System can be divided into 13 thirdorder sequences and the Carboniferous to the Permian Chuanshanian Series can be grouped into 6 thirdorder sequences), many thirdorder sequences from the Devonian to the Permian Chuanshanian Epoch are absent. Therefore, the Wudong section of the Devonian System to the Permian Chuanshanian Epoch is of a typical example that the hiatus is larger than the deposits, which might be resulted from the stronger response of regression than that of transgression. As the result of the largescale and slowspeed transgression in the transitional period from the Carboniferous to the Permian, the study area together with the adjacent areas became a sea area. This transgression is genetically related to the thirdorder rise of sealevel changes of the SQ19. Therefore, divisions of thirdorder sequences of the Permian Yangsingian and Lepingian are similar to those in the southern part of Guizhou as well as in Guangxi.

    Deformation Characteristics and the ESR Dating of Chengkou-Fangxian Fault Zone in the Qinling area
    XU Ya-jun,YANG Kun-guang,MA Chang-qian
    2005, 19(1):  127-132. 
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    The Chengkou-Fangxian fault zone is on the boundary of the Qinling Orogen and Yangtze Plate.The fault zone shows an arc-structure extruding towards SW, which composed the Dabashan tectonic arc. The macrostructures show that this fault zone thrusts strongly from north to south.The macrostructures and microstructures of these fault rocks reveal that the deformation mechanism of this fault zone is characterized by its brittle shallow. The finite strain measurements show that these rocks suffered a low-middle intensity deformation. Eleven quartz veins in the fault zone are dated by the Electron Spin Resonance(ESR), and their ages are distributed in the three stages (240-230 Ma,165-130 Ma,70- 60 Ma). Seven of them have ages from 165Ma to 130 Ma, indicating that the climax activity of this fault zone takes place at the Middle to Late Jurassic(165-130Ma).

    Geochemical Features and Tectonic Significance of the Alkali-Basalts from Ji’an-Taihe Basin,Jiangxi Province
    YU Xin-qi,SHU Liang-shu,DENG Guo-hui,WANG Bin,ZU Fu-ping
    2005, 19(1):  133-140. 
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    New found basalt crop is located near the Nanxi Town, Taihe County, south of Ji'an-Taihe Basin, middle Jiangxi Province. With brown-grey and dark green color, the fresh basalt has compacted texture and some blisters and amygdules. Microscope observation reveals that the rocks have intergranular textures,more than 60% basic plagioclases, filling with olivines and augites, less than 5% almond-shaped calcites, and weak corrosion. According to its geochemical features, the basalt belongs to alkalibasalt, produced by quick regional extension within a plate. Rb-Sr and Sm-Nd isotopic composition of the basalt are as follow:(87Sr/86Sr)i =0.704 1-0.704 8 and εNd(t)=+3.78-+4.38, indicating that the magma came from the deficit mantle and had not mixed with crust material. The zircon solution U-Pb geochronological data of(139±0.7)to(143±1.1)Ma for the alkali-basalt indicates that mantle-reached strike-slip faulting along northeast-striking Ganjiang Fault and Wuchuan-Sihui Fault was active from early period of Early Cretaceous under the extensional background of the area

    Geochemical Research on Tectonic Environment of Early Cambrian Granites in the Huzhong Area of Heilongjiang Province
    WANG Yan,REN Feng he,ZHOU Xing fu,YANG Xiao ping,LI Yang chun
    2005, 19(1):  141-146. 
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    The petrographic type of the Early Cambrian granites in the Huzhong area of Heilongjiang Province, is proved to be monzonitic granite, the Early Cambrian granites are divided into four intrusive periods based on the cognate magma evolution theory,and the rock structures show  that the granularity evolutive tendency is from fine grain to coarse grain in the texture. The character of rock geochemistry shows that SiO2>70%, Na2O/K2O <1,and the rocks attribute calcic-alkalic rocks, corindon occurs and diopside does not occur in the standard minerals, the rocks attribute granites of  S type;δ(Eu)>0.5 shows the rocks belong to weak depletion on Eu,87Sr/86Sr>0.706 indicates the Early Cambrian granites were fomed by the old crust melting.Various of rock geochemical indexes show that the rock's geochemical characteristics are the same as collision granites, and the Early Cambrian granites conform to collision granites of Tibet and Oman. The magmatic activity of collision granites  provides the information about the tectonic dynamics from the continental margin epicontinental of the south of Erguna block in the Neo-proterozoic to Early Cambrian.

    Genesis and Geological Significance of Cherts in Jinshan Mine, Jiangxi Province
    LIU Zhi yuan, JIN Cheng zhu
    2005, 19(1):  147-151. 
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    Based on the detailed field geological survey and comprehensive petrology and major elements, trace elements, REE composition studies, the authors discuss the genesis and the tectonic environment of cherts in the Jinshan mine. The results of analysis indicate that cherts show hydrothermal sediment characteristics of relatively low contents of  Al2O3,TiO2  and relatively abundant elements of As, Sb, Hg, Au, Ag, W and Pb. Rare-earth elements are characterized by a low content, Eu negative anomaly, Ce low positive anomaly and HREE relative enrichment, which suggest that there exists an entry of terrigenous constituent during the formation of these cherts. In a series of discriminant diagram of cherts, the samples fall into the hydrothermal sedimentation field, showing that they are formed in a continental margin environment. Several ratio values of Fe/Ti,(Fe+Mn)/Ti, Al/(Al+Fe+Mn), MnO/TiO2 and δ(Ce)also indicate the same characteristics. The hydrothermal sediment cherts, which suggest that the complex tectonic evolution once occurred in the area, are found. There are a series of fault basins, which were formed by Caledonian tectonic event in Late Palaeozoic in the northeast of Jiangxi Province. At the same time there came into being hydrothermal exhalative mineralization in the Jinshan gold deposit. The Jinshan gold deposit suffered superposed reconstruct by hydrothermal mineralizing process in the Palaeozoic era.

    A Remote Sensing Method Monitoring the Oasis Changes in Desert
    GONG Bin, WAN Li, HU Fu Sheng, JIN Xiao mei
    2005, 19(1):  152-156. 
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    A method is provided to monitor the changes of area covered by vegetation with time on the regional scale by using meteorological satellite images. The images, which are corrected by BareSand Soil Line, are used to get NDVI that indicates the vigor and amounts of vegetation. A new method, which is called Equal Area Method, is given to calculate the area of oasis in different years,and is applied to Ejina oasis.It is shown that the area of this oasis has decreased in recent 14 years.