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2009, Volume 16 Issue 1
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Determination of inner pressure for fluid inclusion by Raman spectroscopy and its application ZHENG Hai-Fei JIAO Er-Wei YANG Yu-Ping DUAN Ben-Yu 2009, 16(1): 1-5.  Abstract ( 2234 )   PDF (836KB) ( 1153 )   Abstract:  Using Diamond Anvil Cell combined with the micro Raman spectroscopy, the author has obtained the quantitative relationships among Raman shifts,  pressure and temperature for the vibration of O—H in H2ONaCl, C—O in CO2-3, S—O in SO2-4 and C—H in nheptanecyclohexane. On the basis of these relationships, we can determine the inner pressure for the fluid inclusion and further determine the isochore. It is not only helpful in obtaining the forming temperature and  pressure for minerals, but also able to provide the information of the chemical composition of the fluid inclusion. Related Articles | Metrics

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A preliminary study of oil generation kinetics using diamond anvil cell technique SUN Qiang ZHENG Hai-Fei 2009, 16(1): 6-10.  Abstract ( 1691 )   PDF (647KB) ( 862 )   Abstract:  Diamond anvil cell (DAC) is widely employed in high pressure research field since its invention; it has become an important approach in studying the structure and properties of material under high pressure. In addition, oil generation kinetics is applied in the assessment and exploration of sedimentary basin. In this article, the principle of oil generation kinetics is explained, and the experimental approach to obtain the kinetic parameters is also discussed. Additionally, we have analyzed the application of DAC to the study of oil generation kinetics. Related Articles | Metrics

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Hydrocarbonbearing inclusions synthesized in carbonate at the temperature and pressure of natural reservoir: Some important implications for the study of petroleum geology CHEN Yong GE Yun-Jin ZHOU Yao-Qi LIU Chao-Yang ZHOU Zhen-Zhu MAO Cui 2009, 16(1): 11-16.  Abstract ( 1857 )   PDF (937KB) ( 938 )   Abstract:  We have successfully synthesized hydrocarbonbearing inclusions in carbonate at the temperature and pressure of 150 ℃ and 40 MPa, which are near the condition of natural reservoir underground 4 kmAll synthetic hydrocarbonbearing inclusions have been analyzed by microscope and microfluorescence and fourier transform infrared spectroscopyThe results show that the synthesized hydrocarbonbearing inclusions are very similar to those in real reservoirsOur experiments give us four important insights, including: (1) immiscibility of oil and water is the main reason for hydrocarbonbearing inclusions and aqueous inclusions distributed in different fractures; (2) rapid accumulation of oil and gas can be recorded by fluid inclusions; (3) the study of synthetic hydrocarbonbearing inclusions at the temperature and pressure of real reservoir will offer references and standards for the analysis of fluid inclusions in reservoirs; (4) experiment of synthetic hydrocarbonbearing inclusions is a good method for understanding the mechanism of oilwaterrocks interreaction in reservoirs. Related Articles | Metrics

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High pressuretemperature experiment and insitu measurement technology WANG Hui-Yuan ZHENG Hai-Fei 2009, 16(1): 17-26.  Abstract ( 1612 )   PDF (1514KB) ( 2217 )   Abstract:  Recent progress in both high pressuretemperature experimental techniques and insitu measurement techniques under high pressure temperature were discussed. In this paper, we focused on the following aspects: (1) The characteristics of both static and dynamic high pressure techniques, i.e. diamond anvil cell, large volume press, and autoclave; (2) Spectroscopy used in high pressure techniques for insitu measurement, including Raman, Infrared, Xray diffraction and synchrotron radiation; (3) Experimental methods for determining elastic wave velocity under high pressure-temperature, i.e. ultrasonic method, Brillouin Scattering, Nuclear Resonant Inelastic XRay Scattering; (4) The recent development of insitu measurement of electrical conductivity under high pressuretemperature in diamond anvil cell and large volume press. Related Articles | Metrics

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A review of methods of determining pH of fluids at high temperature and pressure SU Gen-Li LI He-Beng LIU Cong-Jiang DAI Li-Dong 2009, 16(1): 27-32.  Abstract ( 1631 )   PDF (791KB) ( 892 )   Abstract:  The pH of fluids play an important role in the dynamics and equilibrium between minerals and fluids at high temperature and pressure. This article reviews various methods of pH determination of aqueous fluids at elevated pT conditions. These methods include potential measurement and electrical conductivity measurement of electrochemical cell and calculation of pH from fluid compositions. Over the past few decades considerable progress has been made in developing practical potentiometers for measuring pH in high temperature aqueous solutions. Platinumhydrogen electrodes are very precise for pH measurement of various solutions at relative low temperatures. Potentiometer based on ceramic membrane such as yttriastabilized zirconia(YSZ)membrane sensor is one of the most significant achievements in high temperature potentiometer. Using chemical analyses and 25 ℃ pH measurements, the pH and distribution of aqueous species at high temperature can be calculated by solving simultaneous mass action equations for complexes equilibria and mass balance equations. Numerical errors and uncertainties in thermodynamic data and analytical errors can effect these computed values. Electrical conductance measurements of aqueous solutions at high temperatures and pressures provide unique information concerning the extent of ionic interaction of ions in solutions. From the results of electrical conductance measurements of aqueous solution we can obtain pH values at relative high temperature and pressures. Related Articles | Metrics

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Water in the Earth's interior and abiotic formation of hydrocarbon CHEN Jin-Yang LIU Gui-Xiang JIN Lu-Jiang 2009, 16(1): 33-40.  Abstract ( 1420 )   PDF (827KB) ( 914 )   Abstract:  Water widely exists in the deep Earth interior. Owing to high temperature and high pressure, it presents many unique physical and chemical properties, and it is of great significance in abiotic formation of hydrocarbons and in their migration. The generation of H2 or O2 resulted from the reaction of water with inorganic mineral has great impact on the equilibrium of COH fluid, which plays an important role in the origination and stability of hydrocarbons in the deep earth. The hydrothermal fluids not only provide excellent solvent for organic reactions, but also participate in the reaction with carbonates or metal carbide to generate hydrocarbons. FischerTropsch synthesis is an important mechanism for prebiotic origin of organic compounds and hydrothermal organic geochemical reaction. The main source of H2 to FischerTropsch reaction is generated from the reaction of mineral with water, which is the important way of abiotic formation of hydrocarbons. Related Articles | Metrics

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Fluids and mineral interactions in extreme conditions of the Earth interior:  Insitu observation of the deep Earth fluids using diamond anvil cell ZHANG Rong-Hua ZHANG Xue-Tong HU Shu-Min 2009, 16(1): 41-52.  Abstract ( 1726 )   PDF (1931KB) ( 830 )   Abstract:  Recent ultrahigh pressure and high temperature experiments provide a new opportunity to gain an insight into the fluids,fluid and matter interactions in the extreme conditions of the deep Earth interior. Insitu observations of the matter under ultrahigh pressure and high temperature conditions as in the Earth interior by using diamond anvil cell connected to spectrometer and microscope, combined with synchrotron radiation technique, may obtain new data and message of their molecular structures and natures in atomic scale and in kinetics. The nature of Earth fluids would be changed by the variations of the temperatures and pressures of their locations. It is well known that the properties of water in the critical region may show anomalies in many of its physical properties. For example, the density or dielectric constant of water may drop with increasing temperature. The molecule structures of aqueous solutions (NaClH2O) at high temperatures and pressures(800 ℃,3 GPa) have been examined by insitu observation using diamond anvil cell connected to FTIR spectrometer combining with synchrotron radiation technique. The sharp and strong O—H stretching vibration at 330 ℃ near the critical point of water proves the break down of the hydrogen bonding network. Within and near the critical region, the rapid decrease in the dielectric constant and density of water results from the destruction of the hydrogen bond network of the water molecules. The O—H vibration frequency increases with temperature. Experiments demonstrate that the nature and the structure of the Earth fluids will change with depth. As passing through the critical state,the anomalous properties of fluids will be affected by the variations of water molecule vibrations and the break down of hydrogen bond network in the critical state. Key words: ultrahigh pressure and high temperature in Earth interior; critical state; fluid nature; molecular spectroscopy Related Articles | Metrics

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Critical fluids and mineral(rock)interactions in extreme conditions of the Earth interior ZHANG Rong-Hua ZHANG Xue-Tong HU Shu-Min 2009, 16(1): 53-67.  Abstract ( 1837 )   PDF (2501KB) ( 721 )   Abstract:  Insitu observations of the matter under ultrahigh pressure and high temperature conditions as in the Earth interior by using diamond anvil cell connected to spectrometer and microscope, combined with synchrotron radiation technique, may obtain new data and message to reveal the kinetic mechanism of watermineral and waterrock interaction at the extreme conditions. The nature of Earth fluids would be changed by the variations of the temperatures and pressures of their locations. It is well known that the properties of water in the critical region may show anomalies in many of its physical properties. For example, the density or dielectric constant of water may drop with increasing temperature. NaClH2O at high temperatures and pressures(800  ℃,3 GPa) have been examined by in situ observation using diamond anvil cell connected to FTIR spectrometer. The sharp and strong O—H stretching vibration at 330  ℃ near the critical point of water proves the break down of the hydrogen bonding network. Kinetic experiments of minerals (albite, quartz, diopside, actinolite, etc.) and rock (basalts, syenite) in aqueous solutions were performed by using fluid through apparatus at temperatures of 20 to 435  ℃ and pressures of 23 to 35 MPa. We found that the dissolution rates exhibit a fluctuation during crossing the critical state of water. The dissolution rates of silicate minerals in water increase with increasing temperature until reaching the critical state of water. Then they decrease with continued increasing temperature. The dissolution rate reaches a maximum value in the critical region (300400  ℃). The fluctuation of dissolution rates are affected by the variation of water properties. As the deep metalbearing supercritical fluids rise up, they will have an opportunity to pass through the LV immiscibility region. We performed a series of experiments of LV immiscibility region of metalbearing fluids, and found Au, Cu, Sn, W, and Zn could be partitioned in liquid and vapor phases in the subcritical states of the fluids. Experiments demonstrated that the nature and the structure of the earth fluids will change with depth. As passing through the critical state,the anomalous properties of fluids will drive a fluctuation of dissolution rates of silicate minerals in water. In addition, both vapor and liquid phases could carry metals up to the Earth surface as the fluids were separated into liquid and vapor phases in the LV immiscibility field. Related Articles | Metrics

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Gaseous transport of mineralizing elements and experimental study ZHANG Sheng XIONG Xiao-Lin T.M.Seward 2009, 16(1): 68-75.  Abstract ( 1499 )   PDF (937KB) ( 979 )   Abstract:  More and more field observations and experimental data show that gas plays a certain role in the transport and enrichment of mineralizing elements. Sublimates and condensates formed from high temperature volcanic gases are enriched with various magmatic components and oreforming metals. Mineralizing elements are also detected in moderate to low temperature water vapor occurring in geothermal field. The vaporrich fluid inclusions are enriched in Cu and Au even more than the coexisting brine inclusions in some porphyry coppergold deposits. The theoretical assumption of gaseous transport of metals as simple chlorides, fluorides, sulfides, oxyacids and atoms underestimates the capacity of the gas phase to transport metals below 400 ℃, hence the solvation or hydration should be taken into account , which is demonstrated by the solubility experiments of silver, gold, copper, tin, molybdenum and tungsten in hydrothermal vapors. Thermodynamic modeling based on the experimental data indicates that hydrothermal vapors can transport sufficient metals to form economic epithermal and porphyry deposits. In addition, experiments show that the partitioning of arsenic and boron into vapor phase from liquid is also related to the hydration, and the vapourliquid distribution coefficients increase with temperature and vapor pressure. Undoubtedly, the theory of oreforming metal transported in hydrothermal vapor is significant to the understanding of the forming mechanism of metal deposit and the development of the geogas prospecting methods such as deeppenetrating geochemistry. Related Articles | Metrics

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Rheological complexity of mafic rocks and the effect of mineral component on creep of rocks ZHOU Yong-Qing HE Chang-Rong HUANG Xiao-Ge SONG Juan SANG Jie-Na KONG Hua 2009, 16(1): 76-87.  Abstract ( 1458 )   PDF (1611KB) ( 861 )   Abstract:  In the rheological experiments for natural mafic rock samples  there will be semibrittle deformation under lower temperature ranges, in contrast, there will appear melts at grain boundaries in the  sample under higher temperatures, and this could greatly effect  the rheological behaviors of samples.  In the literature, the stress exponent n is mostly reliable and with high recurrence rate, the activation energy Q is, in some extent, reiterative, however, the coefficient  A is poorly reiterative .  We performed creep tests using 6 kinds  of samples with different mineral components. The mechanical data show that it is more complicated for the effect of mineral component on rheology of rocks than physical models based on   flow laws of two phase and polyphase aggregates determined by endmember components. For the sample consisted of plagioclase, clinopyroxene and hornblende, rheological behaviors are controlled by plagioclase and clinopyroxene when the content of hornblende is less than 10%, however,  the role of hornblende could become significant for deformation of samples when the content of hornblende is higher than 10%. For the sample with major mineral of plagioclase, quartz and hornblende, rheological behaviors are dependent on plagioclase and hornblende when content of quartz is less than 10%, but  when plagioclase content is near 70% it will decide the deformation behaviors of  the  samples. In contrast to that, quartz could  completely control the creep of samples when its content  is higher than 20%.   The most effective method to study rheology of mafic granulite is  to perform creep tests using natural gabbro (or diabase) as well as using hot pressed  synthetic samples prepared from the major mineral components extracted from  mafic granulite. Related Articles | Metrics

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Petrogenesis of  two kinds of Cenozoic ultrapotassic volcanic rocks in Qinghai-Tibet Plateau: Constraints from experimental petrology and geochemistry CHI Xiao-Guo LIU Jian-Feng DIAO Zhi DONG Chun-Yan LI An-Rong DIAO Yuan-Dong DIAO Xiu-Hu 2009, 16(1): 88-98.  Abstract ( 2085 )   PDF (1708KB) ( 934 )   Abstract:  Two kinds of Cenozoic potassicultrapotassic volcanic rocks of QiangtangMangkangDianxi and Gangdise are distributed in QinghaiTibet Plateau. The peak time of QiangtangMangkangDianxi ultrapotassic magmatism is 4030 Ma, and the main rocks have the characteristics of high content of MgO and low content of CaO and Al2O3 as typeI ultrapotassic rocks, while the 3024 Ma magmatism of middle and west Qiangtang area show the characteristics of typeⅢ potassicultrapotassic volcanics, which have low content of SiO2, high content of CaO and Al2O3, and low MgO/CaO ratio. The Cenozoic ultrapotassic volcanics of Gangdise also possess the characteristics of typeI ultrapotassic rocks in high content of MgO and low content of CaO and Al2O3, with forming time between 2512 Ma. Through analysis of the experimental data about ultrapotassic rocks, typeI ultrapotassic rocks came from the source region of phlogopite harzburgite that had undergone metasomatism of fluid (melt) enriched in silica and potassium; while the source region of typeⅢ potassicultrapotassic volcanics is carbonated peridotite mantle bearing potassic amphibole. The NangqianDianxi typeI ultrapotassic volcanic belt is strictly controlled by Honghe strikeslip fault zone in space. typeI ultrapotassic magmatism occurred during 4028 Ma, and the 16 Ma magmatism is translated into potassic basalt with OIB characteristics. The transition of source region from lithospheric mantle to asthenosphere indicates the thinning of lithospheric mantle and upwelling of asthenosphere caused by large scale strikeslip fault, which is the major controlling factor for decomposition melting of phlogopite in the metasomatized lithospheric mantle to generate the typeI ultrapotassic magmatism. The magmatism of 3534 Ma in middle Qiangtang area is the eruption of sodic alkaline basalt mainly from asthenosphere, and the 3024 Ma typeⅢ potassicultrapotassic magma was originated from lithospheric mantle. The transition of magmatic source indicates the activities of CO2rich fluid caused by the upwelling of asthenosphere is the major controlling factor in causing ancient metasomatized lithospheric mantle to warm up and melt to generate typeⅢ potassicultrapotassic volcanics. The upwelling mechanism of asthenosphere may be related to the breakingoff of subducted slab or delamination of lithospheric mantle.  Related Articles | Metrics

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The simulation test of granite uranium mineralization LIU Zheng-Xi LIU Gong-Xu 2009, 16(1): 99-113.  Abstract ( 2591 )   PDF (2091KB) ( 905 )   Abstract:  Based on the theory of “uranium preconcentration system” and the theory of precipitation, the author has conducted the “partial fusion experiment” of uranium productive granite and its mother rock. The result shows that  the mother rocks for forming uranium productive  granite are originated from the sedimentary rocks of Cambrian and the Lower Palaeozoic, etc. The test indicated that the uranium distribution coefficient (Kfm) between the uranium productive granite fluid (f) and the coexisting fused mass (m) at magma temperature is remarkably smaller than 1, showing that the uranium is intensively concentrated in the fused mass, and the continuous remelting can make the uranium content increase in granite. During the period of magma crystallization, the distribution coefficient (Kfc) between fluid (f) and crystalline fused mass (c) increases with the advance of crystallization, indicating it is favourable for forming the hydrothermal uranium deposit. By analyzing the uranium distribution coefficients of different crystals, we found that the uranium distribution coefficient is the largest, when ferruginous material and uranium mineral crystals are coexisting. The experiment results are concordant with the fact that uranium content is higher when the uranium productive granite contains more uraninite and pyrite, which is consistent with the fact that biotite captures uranium during the crystallization. The experiment of uranium mobilization in the period of preore alteration before mineralization shows that about 3％30％ uranium is released when the biotite is converted into muscovite (muscovitization). During the granite muscovitization, about 30％60％ uranium will be released from the total rock and 14％21％ uranium will be released from zircon; the uraninite is disintegrated and parts of them are dissolved. The experiment indicates that the total uranium which migrated into the solution is (104130)×10-6. Hydrothermal experiments of waterrock reaction exhibit that in the solution of a sealed system, the dissolution of uranium increases (up to 23 orders) with pressure decreasing. This conclusion smashed the traditional view point that the uranium will precipitate when pressure is decreased. New conclusions have been drawn from the experiments of hydrothermal uranium mineralization: (1) Moderate decarbonation is favourable for uranium precipitation and also favourable for “uraniumsilicon separation”  from the “uraniumsiliconcarbonate” system. (2) The key factor for uranium precipitation is the remarkable decrease in the pH of the mineralization solution. The experiments have confirmed and developed the theory of the preconcentration system of strata and granite masses, and have a great significance for uranium prospecting. Related Articles | Metrics

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An experimental study of REE partitioning between phosphorusrich peraluminous melt and coexisting aqueous fluid at 1 kbar and 800 ℃ ZHANG Hui TANG Yong LIU Cong-Jiang CHEN Jian-Feng 2009, 16(1): 114-124.  Abstract ( 1581 )   PDF (1309KB) ( 730 )   Abstract:  Fluidsaturated experiments were conducted to investigate the partitioning of 12 REE and Y between the phosphorusrich peraluminous melt and coexisting aqueous fluid at 1 kbar and 800 ℃All runs were conducted in coldseal RapidQuench pressure Vessels (RQV, a kind of “externally heated coldseal pressure vessels”) using water as a pressure medium for durations of 144 hoursThe major chemical compositions of the initial and runproduct glasses were determined by EMPA; REE contents of the initial and runproduct glasses were determined by LAICPMS; REE contents of aqueous fluids were analyzed by ICPMSIt shows that the partitioning coefficients of REE (including La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) between aqueous fluid and hydrous melt (Dfluid/melt) vary from 01×10-4 to 199×10-4, and Dfluid/meltY range from 02×10-4 to 78×10-4, indicating that REE and Y are preferentially partitioned into the hydrous meltsThe relationship of the fluidmelt partitioning coefficients of REEs to the phosphorus contents in the runproduct glasses shows a nearnormal distribution as the contents of P2O5increasing from 019 wt％ to 609 wt％, with the maximum Dfluid/melt corresponding to 144 wt％ of P2O5The fluidmelt REE partitioning coefficients decrease as increasing the atomic numbers of  REE from La to Lu, showing DLREE>DMREE>DHREEgenerallyThe ratios of DY to DHo show no obvious variations with increasing P2O5 contents in the runproduct glasses from 019 wt％ to 609 wt％, keeping a nearly constant value of ～1 (in the range of 091128)The experimental results demonstrate that the interaction of phosphorusrich peraluminous melt with coexisting aqueous fluid could not result in the fractionation between Y and Ho, and among the REEs.Therefore, it is implied that the meltfluid interaction cannot be a candidate for the mechanism of REE tetrad effect during the evolution of peraluminous magmatic system. Related Articles | Metrics

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The partition characteristic of trace elements in the partial melting massive amphibolite at 15 GPa and 950 ℃ MO Fang ZHOU Wen-Ge JIANG Nai FAN Da-Wei CHEN Hai-Gong XIE Hong-Sen 2009, 16(1): 125-133.  Abstract ( 1511 )   PDF (1448KB) ( 636 )   Abstract:  We have performed partial melting experiments on a massive amphibolite sample under 1.5 GPa and 950 ℃ for 101 hours: the sample was collected from Archaean terrain in the northern margin of the North China craton. Experimental products consisted of Hb+Cpx+Gt+Gl and the melt is granodioritic in composition. Trace element compositions of melt and minerals were measured by LAICPMS to get the partition coefficients (Ds) between minerals and melt in the system. The Ds of amphibole, clinopyroxene and garnet are consistent with the previous studies under similar conditions, which indicates that the state of the starting material has little effect on the Ds between minerals and melt. The curve of Ds of REE versus ionic radius for each mineral is coincident with the lattice strain elastic moduli very well. On the whole, the Ds of LILE and LREE for amphibole, clinopyroxene and garnet are lower; the Ds of HREE are higher relatively; garnet is enriched in HREE intensively. Thus, the melt is enriched in LILE, LREE and depleted in HREE. Since there is no rutile in restites, the melt does not show negative Nb and Ta anomaly obviously. The major and trace element characteristics of melt are consistent with the Mesozoic adakitic rocks in the eastern North China craton, which approves the hypothesis that these rocks “could have been derived from the partial melting of ancient lower crust”. Related Articles | Metrics

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Shock melting and fractional crystallization of meteorite minerals under dynamic highpressures and their geochemical significance XIE Xian-De CHEN Ming 2009, 16(1): 134-145.  Abstract ( 1584 )   PDF (2098KB) ( 776 )   Abstract:  We have systematically studied the shock melting and the fractional crystallization of minerals in the three Chinese fallen chondrites, the Suizhou, the Sixiangkou and the Yanzhuang chondrite, using modern micromineralogical techniques. It was revealed that there exist three types of shockinduced melts, namely, the monomineral silicatemelt, the mixed silicatemineralmelt, and the wholerock melt. The research results may be summed up as follows. (1)No obvious differences in major and trace element constituents between the melted and unmelted phases, implying that they are the products of insitu melting. However, the shock melting process did cause the differentiation of some siderophile elements, of light and heavy rare earth elements, and of the element Se in some large melt pockets. (2)Al2O3, Cr2O3, Na2O, and CaO preferentially entered into pyroxene or its highpressure polymorphic majorite (main mineral phase in Earths transition zone), both of which were crystallized from the shock induced silicate melts. (3)The element Al may enter into akimotoite, the ilmenitestructured polymorph of pyroxene and one of the mineral phases in lower mantle, and stabilized as the solid solution. The ELNES analyses revealed that the Fe3+/∑Fe ratio for akimotoite is as high as 067(3). (4)The complete immiscibility of silicate and metalsulfide phases is observed in the whole rock melt, and the latter occurs in the silicate melt as isolated eutectic nodules. No significant differences were found in the concentrations of elements in the melted and unmelted phases, except the Zn,Na,Cr,Co and Cu enrichment in molten sulfide phase and the Na enrichment in molten metal phase. (5)The presence of the FeNi metaltroilitemagnetite assemblage in a melt vein of Sixiangkou chondrite implies that the light elements of S and O may be involved in the Earths core in which FeNi metal is the main mineral composition. (6)Some spherules of Na, Mn and Fe phosphates were observed in the FeNiFeS eutectic nodules in the Yanzhuang chondrite, indicating that the elements of P, Na and Mn may be also involved in the Earths core. The above mentioned phenomena are of important significance in the study of planet evolution, in the Earths mantle mineralogy and geochemistry, as well as in meteoritics itself. Related Articles | Metrics

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Textural development of dehydrationmelting in amphibolite at 1035 GPa and 950 ℃—Effect of pressure and time ZHOU Wen-Ge FAN Da-Wei MO Fang GENG Yi-Suo LIU Yong-Gang XIE Hong-Sen 2009, 16(1): 146-154.  Abstract ( 1439 )   PDF (1443KB) ( 669 )   Abstract:  Two sets of dehydrationmelting with a natural solid amphibolite(56vol.% hornblende, 43vol.% plagioclase), collected from the DabainengLeyu profile in the southern Ailaoshan orogenic belt, Honghe County, Yunnan Province, have been carried out in multianvil apparatus(YJ3000t and JL3600t) at 1035 GPa and 950 ℃ for 20300 h. One is keeping the temperature at 950  ℃ and the annealing time of 100 h, varying the pressure (1035 GPa). The other is keeping the pressure at 30 GPa and temperature at 950 ℃, varying the annealing time (20300 h). The products are inspected with microscope and electron probe. The results indicate that at 950 ℃, annealing time of 100 h, as the pressure in the range of 1015 GPa, the mineral assemblage in the products is clinopyroxene+garnet+melt. As the pressure larger than 15 GPa, the mineral assemblage in the products is clinopyroxene+garnet+melt+Jadeite+SiO2±kyanite. However, at 30 GPa and 950 ℃, as the annealing time in the range of 20100 h, the mineral assemblage of clinopyroxene+garnet+melt+Jadeite+SiO2±kyanite appears successively with time  in the products. As the annealing time longer than 100 h, the mineral assemblage of clinopyroxene+garnet+melt appears in the products. The distribution of the newlyformed minerals and melt is restricted by the texture of the started amphibolite. Based on the mineral distribution and assemblage in the run products at 1035 GPa and 950 ℃ for 20300 h, the textural development of amphibolite during the partial melting process,  the metamorphic reaction, and the garnet corona generation are  discussed. Related Articles | Metrics

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An experimental study of the characteristics of diorite melt composition under different degree of melting MA Rui ZHANG Gang WANG Yang 2009, 16(1): 155-157.  Abstract ( 1643 )   PDF (532KB) ( 1007 )   Abstract:  In order to reveal the characteristics of diorite melt composition under different degree of melting, we performed the experiments to analyse the melt composition while the diorite was being melted under high pressure and high temperature. We came to the following conclusions. When the melting was in the first degree, the composition of the melt is that of a basalt. As the melting degree increasing, the characteristics of the melt composition were being changed from basic to  mediumacidic, from potassiumrich to sodiumrich, and from strong alkaline to alkaline and subalkaline. Related Articles | Metrics

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Tectonic deformation and dynamic metamorphism of coal JU Yi-Wen LIN Gong LI Xiao-Shi FAN Dun-Jia 2009, 16(1): 158-166.  Abstract ( 2009 )   PDF (1035KB) ( 1022 )   Abstract:  Coal is an organic rock which is sensitive to geological environmental factors such as temperature and pressure. Various tectonothermal events of the geological evolution  must have caused a series of changes  in physical, chemical structures of coal and thus formed different tectonically deformed coals. The effect of tectonic stress would induce the brittle and ductile deformation of coal, as well as its dynamic metamorphism at different degrees. Therefore the research about tectonic deformation and dynamic metamorphism of coal is not only of important scientific significance but also very important for the evaluation in resources of coalbed methane and the  prediction of dangerous coal and gas outbursts. Based on the existing research results, different tectonic deformation and dynamic metamorphism in coal have been intensively studied through the Ro,max,XRD and NMR(CP/MAS+TOSS). Also the mechanism of dynamic metamorphism about coal under tectonic stress has been discussed. The results show that,under the influence of tectonic stress to the brittle deformation of coal, the rapid mechanical friction on the plane of fracture in the brittle deformation of coal can be translated into heat energy causing the changes of its chemical structure and composition of coal; while as to the ductile deformation coal,the accumulation of local regional strain energy can result in the failure of its chemical structure. Thus the dynamic metamorphism of different deformational mechanisms would have taken place. Related Articles | Metrics

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Determination of kinetic parameters in open system nonisothermal pyrolysis with ultrahigh temperature for coal and its macerals and geological extrapolation of natural gas LIU Quan-Wei Bernhard.M.Krooss JIN Zhi-Jun WANG Yi Jan Hollenstein 2009, 16(1): 167-172.  Abstract ( 2127 )   PDF (962KB) ( 875 )   Abstract:  Open system nonisothermal pyrolysis experiments at a heating rate of 1 K/min were performed on immature coal samples (Ro=0.4%) from the Tarim Basin, NW China, and on their isolated macerals (vitrinite, exinite, fusinite and semifusinite) in order to determine the kinetics of gas generation (CH4 and N2). Assuming that the generation rate of CH4 and N2 was described by 25 single firstorder reactions with a single preexponential (Ao＝1.0×1013 s-1), a discrete distribution of activation energies was computed by data processing for CH4 and N2. When the activation energies were distributed between 42 and 90 kcal/mol, a model occurred with the dominent activation energy of 60, 52, 50, 70, and 66 kcal/mol for CH4 from coal, vitrinite, exinite, fusinite and semifusinite, respectively; the dominant activation energy for N2 was 74, 108, 100, 108 and 102 kcal/mol respectively when the activation energies were in the range of 60108 kcal/mol. Based on the kinetic parameters derived from laboratory experiments, CH4 transformation ratios were calculated for geological heating rate of 5.3 K/Ma. Gas containing more than 80% of CH4 was formed under these conditions at temperatures in excess of 160 ℃ from coal, whereas the percentage of methane generation from vitrinite and exinite was higher than that from coal. Related Articles | Metrics

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Application of insitu cryogenic Raman spectroscopic technique to fluid inclusion study NI Pei Jean Dubessy DING Dun-Yang WANG Tian-Gang ZHANG Ting 2009, 16(1): 173-180.  Abstract ( 2429 )   PDF (1162KB) ( 980 )   Abstract:  Starting from the successful application of low temperature Raman spectroscopy in studying some geologically interesting hydrates by Dubessy,the insitu cryogenic Raman spectroscopic technique has been used in the study of saltwater system fluid inclusions both synthetically and naturally produced and got great achievement in identification of different dissolved salts,and in the study of fluid phase equilibrium and salinityIt is verified that this technique is an important supplement to the traditional routine microthermometric study of fluid inclusionsThe insitu cryogenic Raman spectroscopic study is becoming a new hot spot in the fluid inclusion research fieldIt will have a broad application in the geofluid studies. Related Articles | Metrics

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The analytical methods for determination of platinum group elements in geological samples DIAO Zheng QI Liang HUANG Zhi-Long HU Cheng 2009, 16(1): 181-193.  Abstract ( 1655 )   PDF (1323KB) ( 961 )   Abstract:  Recent advances in sample digestion, separation and instrumental measurement for analysis of platinum group elements (PGE) in geological samples are reviewedThe low concentration of the PGE in most of the geological samples and their heterogeneous distributions (nugget effect) make accurate determination of PGE very difficultSeparation of PGE from sample matrix are required to reduce nugget effect, to minimize the blank level and detection limits, and to avoid interferencesFire assay, acid treatment, alkali fusion and Carius tube techniques for digesting geological samples, tellurium coprecipitation and ion exchange methods for separating PGE from the matrix, atomic absorption spectrometry(AAS), inductively coupled plasma atomic emission spectrometry(ICPAES), instrumental neutron activation analysis(INAA) and inductively coupled plasma mass spectrometry (ICPMS) for determination of PGE, are reviewed in this paperBecause of the diverse contents and distributions of PGE in geological samples, the analytical methods should be used suitably for routine analysisAccording to the advantages and disadvantages of each method and the experience of our laboratory, this paper also summarizes the suitable digestion and preconcentrating methods for different geological samples. Related Articles | Metrics

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Calculation techniques for soil carbon storage of China based on multipurpose geochemical survey XI Xiao-Huan YANG Zhong-Fang JIA Hua-Ji LI Min 2009, 16(1): 194-205.  Abstract ( 2201 )   PDF (1509KB) ( 1026 )   Abstract:  Soil carbon storage is an important parameter for the study of carbon cycling and global change. Accurate calculation of this parameter is limited by data sources for a long time. Multipurpose geochemical survey, using a scheme of grid sampling and analyses from double layers (surface and deep layer), provides large quantities of precise soil geochemical data for soil carbon storage of China. This paper aims at developing a soil carbon storage calculation method to be used as the criterion for China Geological Survey. A concept of “Unit Soil Carbon Amount  (USCA)”, defined as the amount (weight) of carbon storage in the unit area (4 km2) of multipurpose geochemical survey, was put forward as the basic unit to be cumulated for the calculation of soil carbon storage of a region or the whole China. On the basis of 414 soil profiles from 14 provinces, it was found that soil organic carbon (TOC), differing from soil inorganic carbon and other elements, has a trend of exponentially decreasing with depth. Integral analysis of exponential curve contrasting with the linear model affords the uncertainties of linear model and exponential model for carbon storage calculation. It was found that the integration of TOC with the linear model has errors between +20% to +100%, much higher than that of the exponential model (-10% to +20%). So, it was suggested that the “Unit Soil Organic Carbon Amount (USCATOC)” should be calculated by exponentially integrating TOC between the surface and deep soil layer. However, the “Unit Soil Inorganic Carbon Amount (USCATIC)” may be calculated by linear model. The “Unit Soil Total Carbon Amount (USCATC)” is the sum of the “Unit Soil Organic Carbon Amount” and the “Unit Soil Inorganic Carbon Amount”. It was also suggested that the soil nitrogen storage should be calculated by the scheme of exponential model similar to the organic carbon and that the “Unit Soil Element Amount (USEA)” for all the other elements may be calculated by linear model like the inorganic carbon. Related Articles | Metrics

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Threelevel tectonic model for intraplate earthquakes YANG Wei-Ran CENG Zuo-Xun LI De-Wei GENG Ji-Shan WANG Jie LUO Wen-Hang 2009, 16(1): 206-217.  Abstract ( 1999 )   PDF (4085KB) ( 985 )   Abstract:  Earthquake is a process concerning the longterm accumulation and abrupt release of energy in natureOn the basis of the analysis of the characteristics of intraplate earthquake, we present a threelevel tectonic model for intraplate earthquakeIt consists of a deep uplift structure of the asthenosphere, a middle sandwich structure,ieductilerheological layer sandwiched between competent layers, as the inner part in the middle crust and a shallow brittle faulting structure in the upper crustThe uplifting of the asthenosphere leads to thinning of the lithosphere of the local area around the upcoming epicenterIt supplies the thermal energy and mechanical energy to the epicenter area of the upcoming earthquakeIt increases the temperature and lowers the viscosity of the inner ductilerheological layer in the sandwich structureThe thermal energy increases the competent difference between the highconductive layer and the highresistive layersThe thermal and mechanical energy concentrates at the boundary area between the competent and incompetent layersActive faulting above the sandwich structure accelerates the thinning of the lithosphere and highly concentrating the stress at the boundary between the competent and incompetent layersWhen the active fault reaches the boundary of the sandwich structure, it triggers the intensive intraplate earthquake—inducing an abrupt release of the strain energy accumulated at the boundary areaOn the basis of the model, we design a primary monitoring system for earthquake prediction from the information gaining from the threelevel tectonic system Related Articles | Metrics

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The possible asperities on the XianshuiheAnningheZemuhe Fault Zone: Evidence from background seismicity SHU Ai-Lan XU Ti-Wei GAN Wei-Jun CHEN Gui-Hua 2009, 16(1): 218-225.  Abstract ( 2870 )   PDF (1487KB) ( 1287 )   Abstract:  We mapped b value and local recurrence time TL along the 700km long, leftlateral strike slip  XianshuiheAnningheZemuhe fault zone using the relocated microseismicity between 1992 and 2002 that projected onto the cross section to identify the possible locations of asperities Strong variations in b value are observed along the strike of the fault zone, which are consistent with the surface faulting segmentation in geometry The anomalously short local recurrence time TL and low b value estimates appear on the LuhuoDaofu segment of the Xianshuihe fault zone,  the ShimianMianning segment of the Anninghe fault zone, and  the XichangPuge segment of the Zemuhe fault zone, suggesting that these segments may be the relatively active parts that produce relatively larger microearthquakes than average during the inter seismic interval time With the hypothesis that b value is inversely proportional to the stress, we interpret these three segments as the possible asperities on the fault zone, where the future mainshock will be initiated as the high stress has been accumulated there The risk from the ShimianMianning segment is especially noticeable, which is a wellknown historic earthquake gap The anomalously high b value and long TL estimates on the southeastern segment of the Xianshuihe fault zone along QianningKangdingShimian suggest that this segment may be creeping under low stress at present, and no near future mainshock is expected, although both the historic earthquakes and microseismicity are active there Related Articles | Metrics

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GREAT SCARPS ABOVE SEA COASTS IN GLOBAL MORPHOTECTONICS G.F. Ufimtsev 2009, 16(1): 226-233.  Abstract ( 1622 )   PDF (502KB) ( 967 )   Abstract:  High and extensive tectonic scarps play an important part in global morphotectonics, and are one of the basic tectonic landforms of the southern continental and subcontinental margins and transition zones between the continent and the ocean in the east of Asia. These are proper rear boundaries of continental margins, the geodynamics of which are characterized by rifting on shelves, continental slopes, and marginal oceanic depressions. Great scarps are initiated at the thinning and breaking of the continental lithosphere and have a long phase in the ensuing development, with a successive selfparallel retreat—a process that may be defined as tectonic planation, with the occurrence of a basal surface for shelf sediments.Great scarps are seen located above the passive continental margins and in the rear boundaries of the belt of transition from the continent to the ocean, in the western Pacific. Great scarps are uncommon in intracontinental regions and tend to have additional morphotectonic features at the land elevation and land subsidence boundaries. Related Articles | Metrics

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Deformation record of the change from Indosinian collisionrelated tectonic system to Yanshanian subductionrelated tectonic system in South China during the Early Mesozoic ZHANG Yue-Qiao XU Xian-Bing GU Dong SHU Liang-Shu 2009, 16(1): 234-247.  Abstract ( 3010 )   PDF (5361KB) ( 2107 )   Abstract:  It is commonly accepted that tectonic regimes underwent a tremendous change, during the Mesozoic, from the Tethys tectonic domain to the Pacific tectonic domain in South China, although the timing and geological effects of such a change have been debated. This paper identified two generations of superimposed folds that widely develop in Indosinian to early Yanshanian tectonic layer (DJ12) in South China, and it is found that the earlier generation of folds is well zonated in WE and the later one is distributed in NNE. Based on the analysis of stratigraphic contact relationship and isotopic dating results of Early Mesozoic igneous rocks, it is considered that these two fold generations clearly record two phases of Early Mesozoic tectonic compression in South China: the nearly WE trending fold zones resulted from farfield effect of Indosinian collision or accretion occurred along the northern and southern margins of the South China Block, while the NNEtrending folds were originated from low angle subduction of the paleoPacific plate under the South China Block, which occurred in the time of Middle to Late Jurassic around (170±5) Ma. Crustal thickening caused by these two compressions induced melting and emplacement of Triassic and Late Jurassic granites particularly developed in the Cathaysian Block. The recognition of the two superimposed fold generations in South China is key to understanding the change from the Triassic continentcontinent collisionrelated tectonic system to the MiddleLate Jurassic subductionrelated tectonic system. Related Articles | Metrics

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Discussions on the tectonic setting of Caledonian granitoids in the eastern segment of South China ZHANG Fang-Rong SHU Liang-Shu WANG De-Ci XU Jin-Hai CHEN Wei-Zhou 2009, 16(1): 248-260.  Abstract ( 3006 )   PDF (2147KB) ( 1200 )   Abstract:  Based on our newly firsthand data obtained recently from regional geological survey and previous research results, we have analyzed in detail the geological features, distribution, forming ages and NdSr isotopic characteristics of Caledonian granitoids in the eastern segment of South China.The tectonic setting forming Caledonian granitoids were discussed, which includes the ages of ultramaficmafic rocks and volcanic rocks that outcrop in the study areas, the deposited environment of sedimentary rocks during the SinianOrdovician period, and deformation patterns of the Caledonian structures.Results suggest that the Caledonian granitoids were mainly formed between 410460 Ma corresponding to the period from the Middle Ordovician to the Early Devonian. Geochemically, most of granitoids belong to the Stype that their magma were derived from the partial fusion of continental crust,but a few granitoids show characteristics of type I granitoids that the magma contains mantle materials. There is neither a largescale Caledonian type I granitoids that were related to plate subduction, nor the synchronous island arctype volcanic rocks in the study area; the sedimentary environment during the SinianOrdovician period is mainly a shallow sea and partly a bathyal one. We propose that the tectonic setting forming Caledonian granitoids  mainly belongs to intraplate tectonic environment. Related Articles | Metrics

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Analysis of the direction of shear fracture trend surface in triaxial unequal stress fields LI Dun-Yang LI Pei-Liang 2009, 16(1): 261-269.  Abstract ( 1439 )   PDF (995KB) ( 1045 )   Abstract:  Based on elastic mechanics and CoulombMohr fractural theory, we discussed the extremum of shear difference function, i.e., the difference of shearing stress and shearing resistance on an oblique section, in a triaxial unequal stress field by mathematical analysisWe set the stress field in three different states: the triaxial tensile force, the triaxial compressive force and the maximum and minimum principal stress with one tension and one compression, respectivelyThen, we discussed the relationship of trend surface direction of shear fracture to the three principal stress axes and to the inner friction angle and the cohesion of rocksThe potential direction of shear fracture surface was obtained in different stress statesIn the state of triaxial tensile force, the angle between the shear fracture trend surface and the maximum principal stress axis γ=±(45°-φ/2) and the conjugate angle χ=±(90°-φ)In the state of one tension and one compression, ±(45°-φ/2)≤γ≤±45° and the actual value is determined by the ratio of the tensile principal stress to the compressive principal stressThe shear fracture surfaces under the three kinds of unequal principal stresses are plane surfaces parallel to the intermediate principal stress axesThe existence of tectonic tension stress in geological structures is indubitableThrough the analysis of shear fracture trend surface in the state of one tension and one compression, we could solve the question about the fact that the shear surface conjugate angle χ>±(90°-φ) or even close to 90° encountered in the structural geologic investigation. Related Articles | Metrics

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Reefbanks and reservoirconstructive diagenesis ZHANG Bao-Min LIU Jing-Jiang BIAN Li-Ceng SHEN Yin-Min GU Jin-Hua ZHANG Li-Beng CAO Hong YANG Xiao-Ping 2009, 16(1): 270-289.  Abstract ( 2088 )   PDF (6183KB) ( 899 )   Reefs, reef-mounds and lime mud mounds are all carbonate buildups, and the reefs and banks are important targets for petroleum exploration The reefs, banks and mounds should be divided from each other not only in theory, but also in exploration practice, because of so many differences in sedimentary compositions, fabrics, environments, distribution in time and space, and the characteristics of petroleum geology If the original reef or bank itself was fine reservoir rocks, then it would become a better reservoir after the reservoirconstructive diagenesis The formation of a high quality carbonate reservoir is controlled by two factors: the sedimentary microfacies and the reservoirconstructive diagenesis The first is the basis for the formation of a high quality reservoir, and with the high energy reefbank facies as  the best; the latter includes the cataclasis, the dolomitization and the karstification The dolomitization and karstification are the best for the formation of a high quality reservoir The karstification has the widest distribution, profoundest effect, and plays a vital role in the high quality reservoir forming The karst types are quite rich in the limestone reef or bank reservoir, including synsedimentary karst, penesedimentary karst, supergene karst and hydrothermal karst, and so does the dolomitization reef or bank reservoir The formation mechanism of synsedimentary karst and penesedimentary karst is related to the short time exposing and leaching of the cyclical highfrequency shallowupward sequence when the reefs or banks are forming The supergene karst is controlled by the exposing and leaching of tertiary cyclic sequence type I interface after the reefs or banks forming Thus, there developed a great deal of secondary corrosion pores, corrosion fractures and huge caves besides some original pores remained in the reef and bank reservoir Scarcely there are any original effective pores in reefmounds and lime mud mounds, especially in senkes among mounds, but secondary pores could be formed by karstification, and there would likely develop source rocks with high organic abundance Related Articles | Metrics

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Timing of hydrocarbon fluid emplacement in sandstone reservoirs in Neogene in Huizhou Sag, Southern China Sea, by authigenic illite 40Ar39Ar laser stepwise heating SHI He-Sheng SHU Dun-Zhang QIU Hua-Ning SHU Yu TUN Jian-Yao LONG Jie-Lie 2009, 16(1): 290-295.  Abstract ( 2841 )   PDF (952KB) ( 1375 )   Abstract:  Timing of oil or gas emplacements is a new subject in isotopic geochronology and petroleum geology. The principle of the illite KAr age as expounded by Hamilton et al. is that the illite is often the last or one of the latest mineral cements to form prior to hydrocarbon accumulation, and since the displacement of formation water by hydrocarbons will cause silicate diagenesis to cease, KAr ages for illite will constrain the timing of this event and also constrain the maximum age of formation of the trap structure. In this study, the possibility of authigenic illites 40Ar39Ar dating has been investigated. The illite samples were separated from the Tertiary sandstones in three rich oil reservoir belts within the Huizhou sag by cleaning, fractured by coolingheating cycling，Soxhletextracting with solvents of benzene and methanol and separated with centrifugal machine. If oil is present in the separated samples, ionized organic fragments with m/e ratios of 36 to 40 covering the argon isotopes will be yielded by the ion source of a mass spectrometer, resulting in wrong argon isotopic analyses and wrong 40Ar39Ar ages. The preliminary experiments of illite by heating did show the presence of ionized organic fragments with m/e ratios of 36 to 44. In order to clean completely up the organic gases and obtain reliable analysis results, a special purification apparatus has been established by Qiu et al. and proved valid by the sequent illite analyses. All the illite samples by 40Ar39Ar IRlaser stepwise heating yield stairup age spectra in lower laser steps and plateaux in higher laser steps. The youngest apparent ages corresponding to the beginning steps are reasonable to be interpreted as the hydrocarbon accumulation ages. The weighted mean ages of the illites from the Zhuhai and Zhujiang Formations are 12.1±1.1 Ma and 9.9±1.2 Ma respectively. Therefore, the critical emplacement of petroleum accumulation in Zhujiang Formation in Huizhou sag took place in ca 10 Ma. Later fault activity strengthened the entrance of hydrocarbon fluids into the oil systems based on the data of the fault evolvement history, petroleum system combinations and homogeneous temperatures of fluid inclusions. Related Articles | Metrics

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Lithofacies association and depositional characteristics of the Upper Triassic Xujiahe Formation in Guangan Area, Central Sichuan Basin ZHANG Zhi-Jie LI Wei YANG Jia-Jing YANG Xiao-Ping LI De-Hua 2009, 16(1): 296-305.  Abstract ( 2425 )   PDF (3188KB) ( 860 )   Abstract:  Based on the division of the Upper Triassic Xujiahe Formation and the correlation between the field outcrops and the wells in  Guangan Area, Central Sichuan Basin, we have studied the lithofacies association, depositional characteristics and favorable reservoir in detail Braided delta systems and shoreshallow lacustrine systems are the major types of depositional systems of the Xujiahe Formation in  Guangan Area In the study area of the Xujiahe Formation, 11 lithofacies types and 7 lithofacies associations have been distinguished Delta sandbodies are characterized by the superposition of sandbodies of braided channels with those of subaqueous distributary channel The superimposing belts of major channels obviously control the distribution of favorable reservoirs in the braided delta systems, and the transitional zones from the delta plain to the deltafront are the favorable reservoir zones. Related Articles | Metrics

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Present research status of the deep fluid and their effectiveness on oil/gas generation WU Meng-Hui ZHANG Liu-Beng 2009, 16(1): 306-313.  Abstract ( 1632 )   PDF (1025KB) ( 1653 )   Abstract:  The understanding of the formation of petroleum is deepened as the study of the sedimentary basin is advanced from its framework into its interior fluids and their interactions between different layers. The deep fluid is an important factor influencing the formation of petroleum. Based on the isotopic characteristics of the deep fluid that entered into the basin, two different kinds of style can be recognized. Under the high oxygen fugacity condition, the fluid is composed of CO2+H2O (rich CO2 fluid); under the low oxygen fugacity, the fluid is composed of CH4+H2+H2O(rich H2 fluid). The formation of hydrocarbon from organic matter degradation is a lacking hydrogen process; the  H2 rich fluid can compensate the hydrogen in this process, and increase the production rate of hydrocarbon. The CO2 rich fluid can rebuild the pore space forming a mixed pore network composed of both original and derived pores and improving the physical properties of the reservoir. Related Articles | Metrics

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Nonhydrocarbon origin of Ordovician natural gas in Tazhong of Tarim Basin and its implications for nonhydrocarbon accumulation HAN Jian-Fa MEI Lian-Fu YANG Hai-Jun ZHANG Hai-Jie XU Zhi-Meng GU Jiao-Yuan XU Gong-Feng 2009, 16(1): 314-325.  Abstract ( 1765 )   PDF (2109KB) ( 731 )   Abstract:  In the north of the Tazhong Area in Tarim Basin, a large condensate pool of reefflat facies and a large karst weathering crustal oilgas field have been discovered, which demonstrates a breakthrough in the oilgas exploration in carbonate rocks of Ordovician marine faciesBy using organogeochemical indexes combined with the analysis of the evolution of tectonicsedimentation some good results have been achieved in the study of the effective hydrocarbon source rock and the accumulation processBut as the exploration depth increases, the complexity of fluid distribution becomes a more and more prominent problemThrough the research on the Ordovician oilgas accumulation in the north of the Tazhong Area by dating and analysing the natural gas components and their isotopes, we could sum up the mode of pool formation in Tazhong as follows: There were three periods of formation and two periods of adjustment; oilcharging occurred in the early stage and gasinjection occurred in the later stage; oilgas accumulated in multifashion and oilbearing rocks were widespreadIt is confirmed that the natural gas is mainly the oilcracked gas in the Tazhong Area and it is emphasized that the gasinjection in the later stage is the key to the formation of the largescale gas field in Tazhong Related Articles | Metrics

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Evaluation and analysis of latent heat in rainy season in QinghaiXizang Plateau ZHANG Jie LI Dong-Liang 2009, 16(1): 326-334.  Abstract ( 1826 )   PDF (1995KB) ( 921 )    Combined with the 3″DEM data and the precipitation data in rainy season (from May to September) at 102 weather stations in the east of QinghaiXizang Plateau, we have divided the stations into three classes according to the precipitation distribution with altitude The models of the relationships between the precipitation and various geographical and topographical factors were built up based on regression analysis, and the precipitation and latent heat of condensation in rainy season were evaluated over the past 46 years (19612006) The results showed that the correlation between the precipitation and those factors are remarkable; the correlation coefficients are 069, 082, 090, respectively, which past the 005 confidence test The distribution of latent heat of condensation is inhomogeneous in the east of the plateau, that is, higher in the southeast of the plateau and lower in the northwest of the plateau The east of the plateau is divided into 5 climate subareas by using EOF and REOF methods; the temporal variation in total latent heat of condensation of the east plateau is in consistent with the latent heat of condensation in A,B,E regions, but is inconsistent with the latent heat of condensation in C, D regionsThe total latent heat ranges from 181×1020 J to 268×1020 J; the trend of its variation is increasing; the average latent heat is 219×1020 J. Because of the positive adjusting effect of altitude, longitude and slope gradient and other factors on precipitation in lower altitude regions, the latent heat of condensation in these regions are decreasing since 1990s Because of the positive adjusting effect of slope gradient and the negative adjusting effect of latitude on precipitation in high altitude regions, the latent heat of condensation in these regions are increasing with fluctuations Related Articles | Metrics

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A study of the distribution of the strata during the faultdepression stage and its significance for the petroleum exploration in Songliao Basin ZHANG Shou-Ren ZHANG Sui-An 2009, 16(1): 335-343.  Abstract ( 2085 )   PDF (4222KB) ( 734 )   According to the systematic seismic interpretation, three strata had developed during the faultdepression stage in the Songliao Basin. The developing processes and the original and present distributions of these three strata are very different. During the faultdepression stage, a complete forming process of a basin had happened, not only including the initial splitting phase—The Huoshiling Stage, and the dominating splitting phase—The Shahezi Stage, but also including the fading phase—The Yingcheng Stage. The systematic research on the strata during the faultdepression stage has led to the more accurate forecasting for the source rock, and is of great significance for the deep petroleum exploration. Related Articles | Metrics

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Zircon U-Pb age and geochemistry of granitoids within Jinla Pb-Zn-Ag polymetallic ore field across China and Myanmar CHEN Yong-Qing HUANG Jing-Ning Xiaoming Zhai LEI Yang-Xiang CHENG Zhi-Zhong LI Jian-Rong 2009, 16(1): 344-362.  Abstract ( 3208 )   PDF (2724KB) ( 1012 )    Jinla Pb-Zn-Ag polymetallic ore field across China and Myanma, is tectonically located in the south segment of the Mengtong-Gengma-Ximeng passive continental margin of Proterozoic eraPalaeozoic era，and the eastern margin of the Baoshan.Shantai Massif. The granitoids related to mineralization within the ore field include Laochang amphibole admellite, Menglinshan biotite admellite and Nanla K-feldspar granite-porphyry. This paper systematically presents the characteristics of the major elements, REE and trace elements (including ore-forming elements) of the granites and their isotopic ages determined by zircon SHRIMP dating. The intrinsic connection and genesis of the granites, and the relationships between granites and Pb-Zn-Ag mineralization are discussed. It comes to the conclusions as follows：(1) Among three types of granites, Laochang amphibole admellite and Menglinshan biotite admellite have the same age of (45±1) Ma and likely emplaced in a deeper setting at the earlier stage of tectonomagmatic evolution; Nanla Kfeldspar graniteporphyry has an age of (43.41±0.78) Ma and emplaced in a shallower setting at the later stage of tectonomagmatic evolution.（2）Studies on both major elements and trace elements of the granites, combined with their zircon U-Pb age, such as REE and Zr/Hf，Nb/Ta，Rb/Sr，Rb/Ba，K/Rb，(Rb/Yb)N，Sr*，K* and Zr* show that these granites emplaced in an extension tectonic environment at the age of 43~45 Ma during the later stage of syncollision of the Himalayan orogenic episode, which are the products of crystallization and differentiation from their mother granite magma at different stage of tectonomagmatic evolution. (3) It has been shown in the Al(Na+K+Ca/2) diagram that the Jinla granitoids are all plotted within the area of “S” type of granites, but the samples from Laochang amphibole admellite, Menglinshan biotite admellite and Nanla K-feldspar graniteporphyry are scattered gradually far away from the boundary between “I” and “S” types of granites, implying that the components from the upper mantle gradually decreasing from the Laochang amphibole admellite to the Menglinshan biotite admellite and then to the Nanla K-feldspar granite porphyry. (4) In contrast to granites in China, Nanla K-feldspar graniteporphyry are strongly richer in oreforming elements such as W, Cu, Bi, Sb, Mo, Sn, Ag, Pb, and Au as well as volatile elements F, B, and As than the other two types of granites. In addition to that, the Pb-Zn-Ag ore deposits are spatially associated with K-feldspar granite-porphyry veins in depth within this ore field, which implies that the Kfeldspar granite-porphyry may be closely related to the Pb-Zn-Ag mineralization and may be regarded as visible marks for finding new ore deposits. Related Articles | Metrics

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The influence of the size of marine planktonic foraminifers on the boron isotopic analysis NI Yun-Yan 2009, 16(1): 363-372.  Abstract ( 1550 )   PDF (1294KB) ( 750 )    We have measured the boron isotopic compositions in marine planktonic foraminifers Globigerinoides sacculifer (500600 μm and 300355 μm) and Globigerinoides ruber (300355 μm and 250300 μm) from three tropical ODP sites (Pacific Site 806, Atlantic Site 664 and Carribean Sea Site 999) during the last glacial maximum and the Holocene. Due to the limits of available sample amounts and unexpected boron loss during sample preparation, boron isotopic compositions of small size foraminifers are susceptible and large size foraminifers are better to be used for boron isotopic analysis, especially on glacialinterglacial timescales. Because of the possible enhanced dissolution effects during the last glacial maximum, δ11B in G.sacculifer from both Site 806 and Site 999 are much lower than the expected values. Whereas δ11B in G.ruber are free of the dissolution effects, and can record the changes of seawater pH. The δ11B in G.ruber from the three sites during the last glacial maximum is averagely (1.3±1.2)‰ (2 s.e.) higher than the Holocene values and comparable to the theoretical values (1.6 ‰). Related Articles | Metrics

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The application of multivariate linear regression combined with stepwise regression analysis for CuNi sulfide deposit of Baishiquan FU Yong HONG Li-Jin CHAI Feng-Mei DENG Gang CHEN Yong CHEN Dun-Hua 2009, 16(1): 373-380.  Abstract ( 1766 )   PDF (1568KB) ( 1229 )    Baishiquan Cu-Ni sulfide deposits located in the eastern Tianshan of Xinjiang have attracted the attention of many tectonists, petrologists and ore deposit experts for a long time. However, the mathematical study of the geology of this area is still lacking. On the basis of geological field survey, we have made systematic sampling and geochemical analyses of the rocks, and  systematically studied the relationship between the Cu-Ni variable and the rockforming element variables by the method of multi-variate linear regression combined with stepwise regression analysis, using SPSS statistical software. We established the variable regression equation of Cu-Ni variable and other variables, tested and explained the causes of the formation of the Cu-Ni sulfide deposit of Baishiquan and the magma source and so on. It is of significance for guiding the ore exploration and the application of mathematical methods to geology. Related Articles | Metrics