bluuebunny/crossref_metadata_2025 huggingface dataset:
The Gas Resources Assessment Expert System of the Songliao Basin
Authors: Shengxiang LONG , Chuan WANG , Yuzhan LI
Published: September 2010

Abstract  The gas resources assessment expert system is one of the advanced methods for appraising oil and gas resources. The establishment of a knowledge base is the focal task in developing the expert system. This paper presents a summary of the mechanism and the major controlling factors in the formation of gas pools in the southeast uplift of the Songliao basin. Then an appropriate assessment model is established for trapping the gas resources and a knowledge base built in the expert system to realize the model. By using the expert system to appraise the gasbearing probability of 25 major traps of the Quantou and Denglouku Formations in the Shiwu‐Dehui area, the authors have proved that the expert syster., is suitable for appraising traps in the Songliao basin and similar basins.
The Equilibrium Coefficient Kp and Petroleum Exploration: Design of the New Generation of Petroleum Exploration Instrument
Authors: Weiheng FENG , Yun FENG
Published: September 2010

Abstract  The main reason why the application of nuclear technology in petroleum exploration has not yet been accepted by most exploration workers is that they are not clear about the homologous distribution features of oil and gas fields and radioactive radiation. The authors hold that the disequilibrium of uranium, radium and radon as a natural radioactive series is the basic feature in the use of this technology in petroleum exploration. The invention Gamma‐ray Spectral Measurement of the Equilibium Coefficient Kp and Its Embodiment of the senior author now can readily solve that problem and replace the impedient measure of normalization of uranium and potassium to thorium that had to be proposed before. Application of this impedient measure has some limitations. In areas where the surface is covered by beach or river sands, thorium minerals such as monazite may be concentrated by placering. This could result in local thorium highs that would yield local uranium and potassium lows after normalization to thorium, and these would constitute false anomalies.

This paper elucidates the relation between the equilibrium coefficient Kp and petroleum exploration and points out that immediately over petroleum the radioactive equilibrium is biased with uranium, while at peripheries of the petroleum reservoir the equilibrium is biased with radium; therefore, the true uranium content immediately over petroleum is not lower but higher, and by constrast the uranium content at peripheries of the petroleum reservoir is not higher but lower. This paper further introduces the main technical requirements for the instrument used in petroleum exploration with nuclear technology and the design basis and work procedure of the petroleum‐field effective equilibrium coefficient ground detector and finally introduces the applicability of the detector in petroleum exploration through the distribution features of the equilibrium coefficient Kp of five types of trap‐type petroleum deposits.
Research and Application of New Methods to Oil‐Gas Geochemical Exploration
Authors: Yuanrong CHEN , Guoxiang JIA
Published: September 2010

Abstract  Based on the results of researches and applications for many years, it has been discovered that new methods and techniques for geochemical exploration of oil and gas such as δC, altered carbonate, Hg in absorption phase, Ks, Fe2+, δ13C, fluorescence in two and three dimensions, and N2 and O2 in heat release can give full play in the following five fields: (1) optimization of the favourable target or hollow zones and structural zones in a region; (2) evaluation of oil traps and delineation of prospective oil and gas areas; (3) prediction of deep‐seated oil‐bearing horizons; (4) evaluation of the genesis of oil and gas geochemical anomalies and determination of the types of oil and gas accumulations; (5) forecast of the burial depths of oil and gas pools.
Integrated Reservoir Prediction and Oil‐Gas Evaluation in the Maoshan Area
Authors: Peidong HAO , Xiuqin CUI
Published: September 2010

Abstract  The Maoshan area is an area with well‐developed igneous rocks and complex structures. The thickness of the reservoirs is generally small. The study of the reservoirs is based on seismic data, logging data and geological data. Using techniques and software such as Voxelgeo, BCI, RM, DFM and AP, the authors have made a comprehensive analysis of the lateral variation of reservoir parameters in the Upper Shazu bed of the third member of the Palaeogene Funing Formation, and compiled the thickness map of the Shazu bed. Also, with the data from ANN, BCI and the abstracting method for seismic characteristic parameters in combination with the structural factors, the authors have tried the multi‐parameter and multi‐method prediction of petroleum, delineated the potential oil and gas areas and proposed two well sites. The prediction of oil and gas for Well JB2 turns out to be quite successful.
Application of General Shear Theory to the Study of Formation Mechanism of the Metamorphic Core Complex: A Case Study of Xiaoqinling in Central China
Authors: Jinjiang ZHANG , Yadong ZHENG , Shuwen LIU
Published: September 2010

Abstract: The kinematic vorticity number and strain of the mylonitic zone related to the detachment fault increase from ESE to WNW along the moving direction of the upper plate of the Xiaoqinling metamorphic core complex (XMCC) and the geometry of quartz c‐axis fabrics changes progressively from crossed girdles to single girdles in the same direction. Therefore, pure shear is dominant in the ESE part of the XMCC while simple shear becomes increasingly important towards WNW. However, the shear type does not change with the strain across the shear zone, thus the variation of shear type is of significance in indicating the formation mechanism. The granitic plutons within the XMCC came from the deep source and their emplacement was an active and forceful upwelling prior to the detachment faulting. The PTt path demonstrates that magmatism is an important cause for the formation of the XMCC. The formation mechanism of the XMCC is supposed to be active plutonism and passive detachment. Crustal thickening and magmatic doming caused necking extension with pure shear, and magmatic heating and doming resulted in detachment extension with simple shear and formed the XMCC.
Rare Earth Element Geochemistry of Late Palaeozoic Coals in North China
Authors: Wenhui HUANG , Qi YANG , Dazhen TANG , Xiuyi TANG , Zhigen ZHAO
Published: September 2010

Abstract: Instrumental Neutron Activation Analysis (INAA) was done to determine the abundances of rare earth elements (REE) of 58 samples of Late Palaeozoic Carboniferous‐Permian coals and related rocks in North China. Detailed study of REE geochemistry shows that the ɛREE of most coals studied in this paper is in a normal range between 30×10−6 and 80×10−6 with a mean of 56×10−6. The REE in the Taiyuan Formation in the northern part of North China are much richer than those in the southern part. This is due to the shorter distance to the source area in the north. Moreover, the ɛREE is in positive correlation to coal ash, especially closely related to the content of clay minerals <2 μm in size. This reveals that most REE were carried by terrigenous clastic materials, especially fine clay minerals. In the coals the light REE (LREE) are much richer than the heavy REE (HREE), and the LREE/HREE ratio in coals generally varies from 2 to 8. The LREE/HREE ratio of high‐ash, low‐sulphur coals is higher than that of low‐ash, high‐sulphur coals, and is even higher in the roof and floor rocks, reaching 12 with the highest (up to 21) in pyrite concretions, which shows that the HREE have a stronger affinity to organic matter in a reducing environment influenced by seawater. Furthermore, Eu is generally depleted in coals. The REE chondrite‐normalized distribution patterns are very similar in coals of the whole of North China. From the REE geochemical characteristics it can be concluded that during the formation of Late Palaeozoic Carboniferous‐Permian coals in North China, the supply of terrigeneous materials remained quite stable. The ɛREE in low‐ash, high‐sulphur coals is relatively low and the REE are mainly carried by fine‐grained minerals and organic matter and a certain percentage of REE are adsorbed by organic matter; while the ɛREE in high‐ash, low‐sulphur coals is higher and the REE are mainly present in detritus. The ɛREE of magmatism‐influenced coals is the highest, which suggests that the introduction of magmatic substances may increase the ɛREE, thus causing the REE distribution patterns to show an abnormal feature. Moreover, some harmful elements such as U, W and As usually increase when the coals are influenced by magmatism.
TOF‐SIMS Study of the Hydrocarbon‐generating Potential of Mineral‐Bituminous Groundmass
Authors: Shifeng DAI , Deyi REN , Jianye YANG , Weibiao ZHANG , Fangli JIAO
Published: September 2010

Abstract: The TOF‐SIMS fragment peak ascription of organic and inorganic ions of mineral‐bituminous groundmass of Jurassic source rocks in the Turpan‐Hami and Junggar basins was studied by using the high‐resolution Time of Flight Secondary Ion Mass Spectrometer (TOF‐SIMS). The characteristics of spectrum distribution and constitution of fragment ions of the mineral‐bituminous groundmass are discussed; then the methods of evaluating its hydrocarbon‐generating potential are developed. In addition, the typical parameters, XAL, Yox and ZAR, for indicating the hydrocarbon‐generating potential of mineral‐bituminous and other organic matter in source rocks are put forward to reflect the aliphatic, oxygenous, and aromatic structures. It is confirmed by Rock‐Eval that these parameters are significant in evaluating hydrocarbon generation. Moreover, the detection of the nitrogenous and oxygenous fragment ion, CH5NO3+, in the mudstone formed in semi‐deep lakes and in the carbargilite formed in the arms of lakes reflects the fact that microbes take an active part in biologic degradation.
New Discovery of the Early Cretaceous Volcanic Rocks on the Barton Peninsula, King George Island, Antarctica and Its Geological Significance
Authors: Xiangshen ZHENG , Haiqing SANG , Ji QIU , Jiaqi LIU , Ik LEE Jong , Hyeoncheol KIM
Published: September 2010

Ages determined with the 40Ar/39Ar isotopic system affirms the Early Cretaceous volcanic activity in the Barton Peninsula, King George Island, Antarctica. Two specimens of basaltic andesite collected from the lower‐most volcanic sequence of the peninsula were irradiated and analyzed in different experiments, yielding an identical age spectrum, and two magmatic thermal events of the Early Cretaceous (120.4±1.6 Ma, 119±1 Ma) and Early Tertiary (53.1±1.5 Ma, 52±1 Ma) are distinguished. The former is interpreted to represent the primary cooling age of basaltic andesite, whereas the latter is the thermal reset age caused by the intrusion of granitic pluton. These new ages clearly indicate that volcanism was active during the Early Cretaceous on the Barton Peninsula and that intensive hydrothermal alteration and mineralization of Mesozoic volcanic rocks resulted from Tertiary magmatism.
Basement Characteristics and Crustal Evolution of the Copper‐Gold Metallogenic Belt in the Middle and Lower Reaches of the Yangtze River: Some Isotope Constraints
Authors: Taofa ZHOU , Shucang YUE
Published: September 2010

Studies of the Pb, Sr and Nd isotopic composition of Mesozoic intrusive rocks indicate that the basement of the copper‐gold metallogenic belt of the middle and lower reaches of the Yangtze River has “two‐layer structure” and partly has “multi‐layered structure”, and is inhomogeneous and shows the distinct feature of E‐W provincialism. The calculated model lead ages (t1) are mostly greater than 2600 Ma, and the model neodymium ages (TDM) vary from 953 to 2276 Ma and concentrate in two time intervals: 1800–2000 Ma and 1200–1600 Ma. It is concluded that the basement of the MBYR is composed of the Late Archaeozoic to Middle Proterozoic metamorphic series and that the crust was initiated in the Archaean and continued to grow in the Early and Middle Proterozoic, and the proportion of new crust formed by mantle differentiation during the Late Proterozoic is low.
Characteristics of the Geotectonics in South China and Their Constraints on Primary Diamond
Authors: Wenquan TANG , Chaomin BAO
Published: September 2010

The Asian continent is one of the best places in the world to study continental dynamics. In this region the tectonic framework of the South China plate is related to the activity of the Pacific plate and Indian plate since the Mesozoic. In the South China plate, as the ophiolitic mélange of the middle Proterozoic in the Shaoxing‐Yingtan‐Tengxian‐Beihai faulted zone was confirmed to be a subducting ocean, the evolution of the Yangtze block and Cathaysian block, which are located on both sides of the fault zone, becomes clearer and clearer. A primary diamond deposit, which was first found by Bao Chaomin and his colleagues in Longyou County of Zhejiang Province in 1998, originated from kimberlitoid pipes. The pipes are located in the Cretaceous basin beside this deep fault and the diamond‐bearing pipe was formed deep within a favourable geological structure. Diamond there occurs as octahedral crystals without visual impurities. There are more than 100 similar pipes in the area, which have been poorly studied so far, so this area should have great prospects for diamond exploration.
Pulsation Solution to the Equation of Earth's Gravitational Field (Main Outcome)
Authors: Zhi JIANG , Layers Spherical , Model Density
Published: September 2010

Using d'Alembert equation as the approximation of Einstein's equation, a solution is given in this paper to the time‐dependent gravitational equation of the Earth in consideration of the Earth's features, which describes the characteristics of pulsation of the Earth and the structures of spherical layers of its interior, thus providing a theoretical basis for establishing the idea of mantle pulsation.
Geochronology and Significance of Granites Associated with Gold Deposits in the Jidong Area, China
Authors: Kang GUAN , Zhenkuan LUO , Youshou QIU , Laicheng MIAO , Yumin QIU , MCNAUGHTON Neal , GROVES David
Published: September 2010

The Jidong area is located on the north margin of the North China craton. It is a nucleus composed of the oldest rocks in China. Precambrian metarnorphic rocks with various Phanerozoic granitoids invaded are widespread. Gold deposits here have close spatial relations to granitoids. Some deposits occur within them and others in the outer zone of the contact belt of the intrusion, extending thousands of metres. There have been controversial views in regard to the relations of the deposits to the intrusions although traditional techniques have been used to date the intrusions. In order to solve such a problem, the SHRIMP technique was adopted to date the U‐Pb ages of zircon collected from the Yuerya intrusion which hosts the large‐sized Yuerya Au deposit and Qingshankou intrusion 2 km away from the Jinchangyu (larger‐sized) Au deposit. Analysis shows that the ages of 175±1 Ma and 174±3 Ma for Yuerya intrusion and the age of 199±2 Ma for Qingshankou granite indicate the Early Yanshanian stage of the Mesozoic. The Yuerya intrusion also contains inherited zircon aged at about 2500 Ma, indicating that part of its source materials are Archaean metamorphic rocks. In addition to the SHRIMP data of this study, a great deal of data related to the alteration of Au deposits indicate the formation of the deposits at the Yanshanian stage of the Mesozoic, so the ore formation of Au deposits is inferred to relate to granitic intrusion.
Geochemistry of Alkali‐rich Igneous Rocks of Northern Xinjiang and Its Implications for Geodynamics
Authors: Zhenhua ZHAO , Zhenghua BAI , Xiaolin XIONG , Houjun MEI , Yixian WANG
Published: September 2010

Five nearly E‐W‐trending alkali‐rich igneous rock belts are distributed from north to south in northern Xinjiang, and they are composed mainly of riebeckite, K‐feldspar granite and high‐K and medium‐K calc‐alkaline volcanic rocks and shoshonite. They were mainly emplaced or erupted between the Carboniferous and Permian. The compositions of Sr, Nd, Pb, and O isotopes imply that their principal resource materials are derived from the upper mantle or juvenile crust, indicating obvious continental growth in the Phanerozoic. The trace element association implies that their tectonic settings are within plate and volcanic arc for alkali‐rich granites, and post‐collisional are, late oceanic are and continental are for alkali‐rich volcanic rocks. An archipelago model was suggested for the tectonic evolution in northern Xinjiang. It can be named the central‐Asia‐type orogeny, which is different from the so called circum‐Pacific ocean‐continent‐type tectonics or the Alpine‐Himalayan continent‐continent‐collisional orogeny.
Application of the Landsat‐5TM Image Data in the Feasibility Study of Mudflow Hazards in the Southern Taihang Mountains
Authors: Yanxiao QIAO , Miwen LI
Published: September 2010

The Taihang Mountains area is an area in North China where serious mudflow hazards take place frequently. The hazards often obstrust traffic and make it difficult to carry out conventional ground investigations of the mudflow hazards. This paper introduces the feasibility study of mudflow hazards by using Landsat‐5TM data. The study has achieved a great success through adopting both the faint spectral enhancement technique for mudflow fans (or other depositional areas) and comprehensive study of the environmental background of pregnant mudflows. Thus, remote sensing as a fast, convenient, low‐cost and effective technical method can be used to recognise the situation of mudflow hazards so that effective rescue can be provided.
The Effect of Geologic Structures on the Control of Floods in the Middle Yangtze River Valley
Authors: Qianming Tong
Published: September 2010

This paper discusses the role of geologic structures in the occurrence of floods and how to prevent flood in the middle reaches of the Yangtze River, and gives the author's suggestion that the Luoshan Qiakou be expanded and the land reclaimed from Dongting Lake be returned to the lake in compliance with the law of geology.
Heat Flow Pattern in the Mainland of China and Its Geodynamic Significance
Authors: Yang WANG , Jiyang WANG , Liangping XIONG
Published: September 2010

On the basis of 723 heat flow measurements in the mainland of China and over 2000 data from the global heat flow data set, the authors compiled the heat flow map of the mainland of China and its adjacent areas to exhibit the overall variation of the heat flow pattern in the mainland. The heat flow pattern of the mainland is complex, and can not be simply summarized as “low in the north and west and high in the south and east”. Significant difference exists between eastern and western China in the spatial pattern of heat flow. Divided by the 105°E meridian, heat flow values in eastern China show a westward‐decreasing trend; and a northward variation is observed in western China. The high‐heat flow regions correspond to tectonically active belts such as Cenozoic orogens and extensional basins, where mantle heat flow is high; and the low‐heat flow regions correspond to stable units such as the Tarim and Yangtze platforms. This heat flow pattern is controlled by India‐Asia collision in the west and Pacific plate subduction in the east. The lateral variation in lithospheric strength corresponds to the heat flow variation, and there is a generally reversely proportional relation between heat flow and lithospheric strength in the mainland of China. The mosaic pattern of present deformation in the mainland results from lateral rheological heterogeneity. The good coincidence between weak strength domains and seismic zones demonstrates the intrinsic relation between the strength heterogeneity and regional seismicity pattern in the mainland of China.
Error Propagation in Geochemical Calculations of Groundwater‐Mineral Interactions: A Case Study from the Pingdingshan Coalfield, Henan
Authors: Guangcai WANG , Shu TAO , Zhaoli SHEN , Zuoshen ZHONG
Published: September 2010

The WATEQ4F‐based “multiple step method”, or the method of running WATEQ4F repeatedly, was used to evaluate the error propagation in computations of water‐mineral interactions under the circumstances of constant and varied temperatures due to the uncertainties of input variables. The results show the following: the errors of water chemistry analysis can strongly affect the modelling results of water‐mineral reactions; different input variables (errors) have different effects on the saturation indices (S.I.) of different minerals; in many cases, the S.I. errors of minerals change with temperatures.
Kinetics of Hydrothermal Reactions of Minerals in Near‐critical and Supercritical Water
Authors: Ronghua ZHANG , Shumin HU , Xuetong ZHANG
Published: September 2010

This work presents new experimental results on the kinetics of mineral dissolution in near‐critical and supercritical water in a temperature range (T) from 25 to 400°C and a constant pressure of 23 MPa. Kinetic experiments were carried out by using a flow reactor (packed bed reactor) of an open system. The dissolution rates of albite and magnetite were measured under these experimental conditions. Na, Al and Si release rates for albite dissolution in water were measured as a function of the temperature and flow velocity in the reaction system. The maximum release rates of Na, Al and Si of albite dissolution in the hydrothermal flow systems under different flow velocities were always obtained at 300°C, that is to say, the maximum albite dissolution rates in the flow systems, regardless of different flow rates, were repeatedly measured at 300°C. Results indicate a wide fluctuation in albite dissolution rates occurring close to the critical point of water. The dissolution rates increased when the temperatures increased from 25 to 300°C and decreased when the temperatures increase from 300 to 400°C. At some flow velocities, the dissolution rates rose as the temperature surpassed 374°C. Albite dissolution was incongruent in water at most temperatures. It was only at 300°C that albite dissolution was congruent. The albite dissolution from 25 to 300°C (at 23 MPa) will change from incongruent to congruent, whereas from subcritical 300 to 400°C (at 23 MPa), the dissolution will change from congruent to incongruent. The release ratio of Al/Si (or Na/Si) is positive at T<300°C, and it is negative at T>300°C. The dissolution rates of magnetite in water increased with increasing T until T at the critical point of water or around it. The authors believe that this is caused by the wide fluctuations in water properties under the conditions from the near‐critical to supercritical state.
Mineral Surface after Reaction with Aqueous Solution at High Temperatures and Pressures
Authors: Xuetong ZHANG , Ronghua ZHANG , Shumin HU , Wenbin YU
Published: September 2010

This work presents new experimental results on surface chemistry of reacting minerals and interface kinetics between mineral and aqueous solutions. These experiments were carried out using a flow reactor (packed bed reactor) of an open system as well as a continuous stirred tank reactor, CSTR. The authors measured reaction rates of such minerals as zeolite, albite and carbonate (rhodochrosite, dolomite) in various solutions, and tested corresponding mineral surface by using SEM, XPS, SIMS, etc. This paper mainly presents the experimental results of zeolite dissolution in water and in low pH solutions at room temperature, and dolomite dissolution at elevated temperatures. The results show that the release rates of Si, Al and Na of zeolite are different in most cases. The incongruent dissolution of zeolite is related to surface chemical modifications. The Na, Al and Si release rates for dissolution of albite and zeolite in water and various solutions were measured as a function of temperature, flow velocity, pH and solution composition in the reaction system. In most cases, dissolutions of both albite and zeolite are incongruent. Dissolution of dolomite is also incongruent in most cases and varied with T, pH, and nature of aqueous solutions. For dolomite dissolution, the release rates of Mg are less than those of Ca at high temperatures as T increases from 25 to 300°C. SIMS study indicates that the contents of Al, Na and Si in the leached layer of zeolite or albite surface, change with the distance from the surface, exhibiting a non‐linear behaviour within a thickness range of 1000%. The distributions of Ca, Mg, Mn, H and Cl in the leached surface layer of carbonate have a non‐linear behaviour too.
SHRIMP U‐Pb Dating of Zircons of a Dark Eclogite and a Garnet‐bearing Gneissic Granitic Rock from Bixiling, Eastern Dabie Area, Anhui Province: Isotope Chronological Evidence of Neoproterozoic UHP Metamorphism
Authors: Yuqi CHENG , Dunyi LIU , WILLIAMS I.S. , Ping JIAN , Yuxun ZHUANG , Tianshan GAO
Published: September 2010

The paper reports SHRIMP U‐Pb zircon data of a dark eclogite and a post‐eclogite garnet‐bearing gneissic granitic rock from the Bixiling area, Yuexi County, Anhui Province, in the eastern Dabie Mountains. The eclogite, which is metamorphosed basic tuff, contains very scarce zircons in omphacite or garnet, but more zircons in quartz. They usually exhibit a double‐layered texture, as shown clearly in cathodoluminescence images. Their inner main parts give a 206Pb/238U age of 757±7 Ma, representing the approximate age of the high‐pressure (HP)‐ ultrahigh‐pressure (UHP) metamorphic event during which the eclogite was formed. The outer peripheral parts of the zircons, which have been modified by late‐stage fluids, give an age of 223±3 Ma. The granitic rock contains more zircons of anatectic origin found mostly in feldspar and quartz and usually also showing a similar composite texture. The inner main parts of the anatectic zircons with oscillatory zoning give a 206Pb/238U age of 727±15 Ma for the approximate age of the emplacement of the granitic rock, and their outer parts, an age of 219±3 Ma for a similar or even the same fluid event. It is thus suggested that the HP‐UHP metamorphism of the Bixiling eclogite facies rocks took place during the Neoproterozoic Jinningian, and the Indosinian age values may only represent a late event in the nature of fluid activity.
Control of Melt Structures on Cu–Au Mineralization in Basic‐Ultrabasic Complexes of Northern China
Authors: Wanming YUAN , Xuanxue MO
Published: September 2010

Based on systematic analyses of 72 samples of different basic‐ultrabasic rocks, the present paper discusses the relationship between melt structure and Cu and Au mineralization. It is found that if the NBO/T, NBO, M2+, FeO and MgO values are relatively high and the T, M3+, Fe2O3 and CaO values are low the basic‐ultrabasic melt will be favourable to Cu (Ni) mineralization, but if the former are low and the latter are high it is favourable to Au metallization. Cu ions occupy dominantly octahedra in basic‐ultrabasic melt and the higher the NBO/T, NBO and M2+ values, the more the octahedra in the melt. Au element mainly takes the form of Au+ ions in basic‐ultrabasic melt and the Au+ ions constitute tetrahedral sites together with Fe3+ ions. Therefore, low M2+ and high Fe3+, i.e. high oxygen fugacity, can promote the enrichment of Au+ ions and Au mineralization. Components M+ (other than Au+), Al2O3 and SiO2 in basic‐ultrabasic melt have no effect on metallogenetic species. As mentioned above, in relevant diagrams distribution areas of the characteristic values of ore‐free melt and those of ore‐forming melt are overlapped in different degrees, which possibly indicates that not all the magmas have mineralizing ability. It can be well distinguished whether basic‐ultrabasic rocks are favourable to Cu or Au mineralization or they are just ore‐free rocks by analysing integrated diagrams of the characteristic values of the magmatic melt structure.
Indosinian Foreland Fold‐and‐Thrust Belt Bordering Yunnan and Guangxi, China
Authors: Genyao WU
Published: September 2010

Abstract  Recent discoveries of ophiolites indicate that there must be a Palaeotethyan geosuture zone bordering China and Vietnam, which separates the Vietbac block from the South China subcontinent. The Indosinian foreland fold‐and‐thrust belt bordering Yunnan and Guangxi provided further evidence for the palaeotethysides. The oceanic crust was subducted southwestwards while the magmatic arc migrated northeastwards, and the continent‐arc collision occurred in the Late Triassic with the thrusting being extended towards the north or northeast. The features of thrust‐nappe structure are discussed, which proved the continental margin of the Palaeotethyan ocean there to be a complicated one. A face‐to‐face collision occurred first along the NW‐striking segment and then along the ENE‐striking segment accompanied by transpression or oblique thrusting occurring along the NW‐striking one.
Geochronology and Geochemistry of the Middle Proterozoic Aoyougou Ophiolite in the North Qilian Mountains, Northwestern China
Authors: Zhaochong ZHANG , Jingwen MAO , Guochao ZUO , Jianmin YANG , ROBINSON Paul T.
Published: September 2010

The Aoyougou ophiolite lies in an early Palaeozoic orogenic belt of the western North Qilian Mountains, near the Aoyougou valley in Gansu Province, northwestern China. It consists of serpentinite, a cumulate sequence of gabbro and diorite, pillow and massive lavas, diabase and chert. Ages of 1840±2 Ma, 1783±2 Ma and 1784±2 Ma on three zircons from diabase, indicate an early Middle Proterozoic age. The diabases and basalts show light rare‐earth element enrichment and have relatively high TiO2 contents, characteristic of ocean island basalts. All of the lavas have low MgO, Cr, Ni contents and Mg numbers indicating a more evolved character. They are believed to have been derived from a more mafic parental magma by fractionation of olivine, Cr‐spinel and minor plagioclase. Based on the lava geochemistry and regional geology, the Aoyougou ophiolite was probably believed to have formed at a spreading centre in a small marginal basin. Subduction of the newly formed oceanic lithosphere in the Middle Proterozoic produced a trench‐arc‐basin system, which is preserved in the North Qilian Mountains.
Fluid Inclusion Studies and Geochemistry of Rare Earth Elements of Hydrothermal Fluorites from Pöhrenk, Kirşehir, Central Turkey
Authors: KOÇ Şükrü , REÇBER Ali
Published: September 2010

Fluorite mineralization occurs along fractures and cracks of Middle Eocene and Pliocene limestones and marls in the north and northeast of the Pöhrenk region (Çiçekdagi, Kirsehir). Tb/Ca – Tb/La and Y/Ho ratios were obtained from REE contents of fluorites which have revealed that mineralization is of hydrothermal type. Negative Ce anomalies and positive Eu anomalies reflect that hydrothermal solutions once had high oxygen fugacity. Fluid inclusion studies indicate that homogenization temperatures of mineralization varied between 90°C and 200°C, and hydrothermal solutions are composed of NaCl + KCl + MgCl2 + H2O. In addition, salinity measurements show that hydrothermal solutions were mixed with meteoric or rock formation water. Geologic setting, REE geochemistry and fluid inclusion studies suggest that mineralization was deposited from a solution generated by mixing of magmatic and meteoric water under epithermal conditions.
Analysis of Ore‐controlling Structure in the Qifengcha‐Detiangou Gold Deposit, Huairou County, Beijing
Authors: Bailin CHEN , Zhongjian LI , Faxian DONG
Published: September 2010

The Qifengcha‐Detiangou gold deposit is a medium‐sized deposit recently found in Huairou County, Beijing. It belongs to the altered mylonite type with superimposed quartz vein type and is related to the early Yanshanian magmatic activity. Characterized by multiperiodic activity, the NE‐trending Qifengcha fault is a regional ore‐controlling structure in the area, and gold mineralization develops only in its southeastern part. Meanwhile, gold mineralization is controlled by the Yunmengshan metamorphic core complex. The nearly N‐S‐ and E‐W‐trending low‐angle detachment faults, reformed by the Qifengcha fault in the northwestern part of the core complex, are the main ore‐bearing faults. All discovered gold deposits are located within an area 1.5–4.0 km away from the boundary of the upwelling centre. The N‐S‐ (NNE‐) and E‐W‐trending ore‐bearing faults are ductile‐brittle structural zones developing in shallow positions and subjected mainly to compressive deformation. The structural ore‐controlling effects are as follows. (1) The attitude, shape, and distribution of gold orebodies are controlled by faults. (2) There is a negative correlation between the gold abundance and the magnetic anisotropy (P) of the altered mylonite samples from the deposit, which shows that the gold mineralization is later than the structural deformation. (3) Quartz vein type mineralization is superimposed on altered mylonite type mineralization. (4) In mineralized mylonite, the stronger the ductile shear deformation, the easier the late‐stage gold mineralization to occur and the higher the gold abundance. The richest gold mineralization occurs only around the centre of the fault subjected to the strongest deformation.
Fluid‐melt Inclusions in Fluorite of the Huanggangliang Skarn Iron‐Tin Deposit and Their Significance to Mineralization
Authors: Lijuan WANG , Jingbin WANG , Yuwang WANG , Qian MAO
Published: September 2010

For the first time, fluid‐melt inclusions are found in fluorite of the Huanggangliang skarn iron‐tin deposit (HSID). The fluorite was formed in the main stage of mineralization, named the hydro‐skarnization stage. The inclusions contain various components such as Fe, Mg and Cr from deep sources. The melts of primary inclusions are mainly Ca‐ and F‐rich and those of secondary inclusions tend to become Si‐rich. During this evolution process, the melts and iron daughter minerals decreased and even vanished. These facts reveal that the evolution of the primary mineralizing fluids and the differentiation of the fluids and melts are the main factors leading to the deposition of Fe, Sn and other elements. This discovery confirms the magmatic genesis of the HSID and has filled in the gaps in the research of magmatogenic skarn deposits and furnished new methods for such research. Furthermore, it has enlarged the scope of the research on fluid inclusions.
Rational Exploitation of Resources and Prevention of Geohazards in Karst Regions
Authors: Yaoru LU , Xiling Edited By Zhu
Published: September 2010

This paper discusses the rational exploitation of main resources and prevention of geohazards in karst regions. There exist relationship chains between natural disasters in the earth, which include the chain between geological hazards and climatic hazards, the chain between geological hazards and biogenic hazards as well as the one between geological hazards. Irrational exploitation of all resources will inevitably cause hazards. Therefore it is very important to discuss the problem related to prevention of geohazards by rational exploitation of resources.
Evaluation of Karst Hazards for Civil and Industrial Buildings
Authors: TOLMACHEV V.V. , NESHCHETKIN O.B.
Published: September 2010

The European part of Russia exhibits highly developed sulphate and carbonate karst. It mostly occurs within river valleys with relatively thin covering deposits. These conditions may induce karst collapses, which appear to be the main danger for civil and industrial buildings. Evolution of karst rocks includes several epochs of karst development, which causes complicated distribution of karst caves in karst rocks and, as the result, irregular distribution of karst caves on the surface. Karst hazards prediction is mostly reliable within the geotechnical system “Karst‐Construction”, using probability methods. This approach allows creating 3 types of antikarst protection (alternative design of construction arrangement on a plan, structural protection of a construction and plugging of karst caves beneath construction foundation) and selecting the optimum or the most effective version or their rational combination.
Engineering‐Geological Problems in the Moravian Karst, Czech Republic
Authors: ŜAMALIKOVA Milena
Published: September 2010

The Moravian karst belongs to one of the famous karst regions in Central Europe. It is situated in Moravia in the eastern part of the Czech Republic. According to the geology it is of Devonian age and the main rocks are of different types of limestones. The process of karstification is still active. They are many caves with rich stalagmites and stalactites and the Macocha abyss, the depth of which is 138.5 m. The underground Punkva River flows through the main part of the karst, forming beautiful underground lakes. Typical karst phenomena, such as sinkholes and deep canyons, may be observed on the surface of the terrain. Because of the karstification, water erosion and frost weathering, many steep unstable slopes and walls originated. To solve the stability from a geotechnical point of view is not easy. This requests a special engineering‐geological knowledge and experience.
Palaeoseismic Events in Karst Terrains along the Northern Bulgarian Black Sea Coast
Authors: ANGELOVA Dora
Published: September 2010

The study of the palaoseismic events in the karst terrains of the Bulgarian Black Sea coast is a very important up‐to‐date problem. The investigated region is one of the highest‐energy regions in Bulgaria with established and recorded catastrophic historic and contemporary earthquakes. The terrain is subjected to the influence not only of its own earthquake foci but also of those in Romania and Russia. The palaeoearthquakes that caused considerable disturbances in the karst terrains along the Northern Bulgarian Black Sea coast have left significant traces. They caused disturbances in the environment and the relief (rearrangement of the surface and ground water karst basins, partially or entirely collapsed caves, deformed caves, oil, gas and salt intrusions and gravitationally formed caves). The ecological consequences in historic and contemporary aspects were catastrophic. The palaeoseismic dislocations were formed as a result of global, regional and local geodynamic events related with the destruction of the Moezian platform and the regional extension of the Black Sea basin. The time of their display and their spatial interrelations were established as a result of complex investigations accompanied by original documents.
Petrology of an Arc‐Oceanic Crust Contact Zone in the Laohushan Back‐arc Basin, the Eastern Section of the North Qilian Mountains, NW China
Authors: Houng‐Yi YANG , Yenming WU , Cailai WU
Published: September 2010

Abstract  A contact zone sandwiched between an arc and an oceanic crust was discovered in the Laohushan area in the present study. It consists of a series of north‐dipping imbricated thrust sheets and is exposed on the surface as a narrow arcuate belt, which extends for about 30 km in an E‐W direction and measures about 1–3 km wide. Lithologically, it can be divided into four subzones. Subzone 1 consists of meta‐andesite and metasandstone; subzone 2, psammitic schists; subzone 3, psammitic and pelitic schists, quartz diorite and hornfelses; and subzone 4, metagabbro, epidote amphibolite and pelitic schists. The metamorphism has the following grading sequence: low greenschist facies in subzone 1 ŕ high greenschist facies in subzone 2 ŕ low amphibolite facies in subzone 3 ŕ epidote amphibolite facies in subzone 4. Petrographic and geochemical evidence shows that rocks in subzones 1, 2 and 3 are arc rocks, whereas those of subzone 4 are oceanic crustal rocks. The metamorphic mineral assemblages and especially mineral chemistry of the bluish green amphibole from the pelitic schists and epidote amphibolite of subzone 4 suggest that the rocks of the contact zone were metamorphosed at a pressure of up to 0.69 GPa. It is thought that the Late‐Mid Ordovician oceanic lithosphere of a back‐arc basin was underthrust northerly beneath an arc to a depth of 20–23 km, where the basaltic rocks and gabbro were converted to epidote amphibolite and metagabbro respectively. Then, the root rocks of the arc and these metamorphosed oceanic rocks were brought up to shallower depths by thrust faults to form a contact zone between the arc and the oceanic crust in the Laohushan area.
A Petrographic and Mineralogical Study of Volcanic Rocks from the Mayaxueshan Area, North Qilian Fold Belt, NW China
Authors: Ta‐Wei HSU , Yen‐Hong SHAU
Published: September 2010

Abstract  The Ordovician volcanic rocks in the Mayaxueshan area have been pervasively altered or metamorphosed and contain abundant secondary minerals such as albite, chlorite, epidote, prehnite, pumpellyite, actinolite, titanite, quartz, and/or calcite. They were denoted as spilites or spilitic rocks in terms of their petrographic features and mineral assemblages. The metamorphic grades of the volcanic rocks are equivalent to that of the intercalated metaclastic rocks. This indicates that both the spilitic volcanic rocks and metaclastic rocks in the Mayaxueshan area have formed as a result of Caledonian regional metamorphism. We suggest that the previously denoted spilitic rocks or altered volcanic rocks should be re‐denoted as metabasalts or metabasaltic rocks. The metamorphic grade of the volcanic rocks increases with their age: prehnite‐pumpellyite facies for the upper part of the Middle Ordovician volcanic rocks, prehnite‐pumpellyite to lower greenschist facies for the lower part of the Middle Ordovician volcanic rocks, and lower greenschist facies for the Lower Ordovician volcanic rocks. The P‐T conditions are estimated as T = 240 − 290°C and P = 1.5 − 4.5 kbar for the lower part of the Middle Ordovician rocks, and T = ∼ 300°C for the Lower Ordovician rocks. The variations of mineral assemblages occurring at different domains of the volcanic rocks were controlled by the variations of the effective bulk composition in those domains during metamorphism. The geochemical characteristics of Mg‐Al chromite in the Mayaxueshan volcanic rocks are consistent with an origin of island arc environment.
A Report on a Biotite‐Calcic Hornblende Geothermometer
Authors: Chunming WU , Yusheng PAN , Kaiyi WANG , Jian ZHANG
Published: September 2010

Abstract  This paper presents a biotite‐calcic hornblende geothermometer which was empirically calibrated based on the garnet‐biotite geothermometer and the garnet‐plagioclase‐hornblende‐quartz geobarometer, in the ranges of 560–800°C (T) and 0.26–1.4 GPa (P) using the data of metadolerite, amphibolite, metagabbro, and metapelite collected from the literature. Biotite was treated as symmetric Fe‐Mg‐AlVI‐Ti quaternary solid solution, and calcic hornblende was simplified as symmetric Fe‐Mg binary solid solution. The resulting thermometer may rebuild the input garnet‐biotite temperatures well within an uncertainty of ±50°C. Errors of ±0.2 GPa for input pressure, along with analytical errors of ±5% for the relevant mineral compositions, may lead to a random error of ±16°C for this thermometer, so that the thermometer is almost independent of pressure estimates. The thermometer may clearly discriminate different rocks of lower amphibolite, upper amphibolite and granulite facies on a high confidence level. It is assumed that there is a ferric iron content of 11.6% in biotite, and that the iron content in calcic hornblende may be calculated according to the method of Dale et al. (2000). This thermometer can be used for medium‐ to high‐grade metabasites and metapelites.
A Large Ductile Sinistral Strike‐Slip Shear Zone and Its Movement Timing in the South Qilian Mountains, Western China
Authors: Zhiqin XU , Haibing LI , Wen CHEN , Cailai WU , Jingsui YANG , Xiaochi JIN , Fangyuan CHEN
Published: September 2010

Abstract  There is a large ductile shear zone, 2 km wide and more than 350 km long, in the South Qilian Mountains, western China. It is composed of volcanic, granitic and calcareous mylonites. The microstructures of the ductile shear zone show nearly E‐W extending subvertical foliation, horizontal and oblique stretching lineations, shearing sense from sinistral to oblique sinistral strike‐slip from east to west, “A” type folds and abundant granitic veins. Measured lattice preferred orientations (LPOs) of the mylonitic and recrystallized quartz of the granitic mylonite in the west segment suggest a strong LPO characterized by the dominant slip systems {10times10}  formed at high temperature (>650°C). K‐feldspar of the mylonite shows an 39Ar/40Ar high‐temperature plateau age of 243.3±1.3 Ma, and biotite, 250.5±0.5 Ma, which represent the formation age of the ductile shear zone. The 39Ar/40Ar plateau ages of 169.7±0.3 Ma and 160.6±0.1 Ma and the 39Ar/40Ar isochron ages of 166.99±2.37 Ma and 160.6±0.1 Ma of biotites in the mylonite represent the subsequent deformation age. These ages indicate that this ductile shear zone is similar to the Altun and South Kunlun sinistral ductile shear zones in its ages of movement, formation, reactivation and duration.
Methods of Studying Petroleum Systems in Residual Basins —A Case Study of Mesozoic and Palaeozoic Marine Basins in Southern China
Authors: Zongju ZHAO , Yan ZHU , Shufeng YANG , Genghai WANG , Yunjun XU , Jialiang FENG , Hongying DENG
Published: September 2010

Abstract  Through an integrated study of Mesozoic and Palaeozoic petroleum geology in southern China and a summing‐up of the results of exploration, the authors tentatively put forward a set of methods of studying petroleum systems in modified residual basins or superposed basins. Its core idea is to put emphasis on the study of the dynamic evolution of petroleum systems. The tempo‐spatial evolution, hydrocarbon‐generating processes and hydrocarbon‐generating intensities and amounts of resources in different geological stages of chief source rocks are mainly deduced backward by 3‐D basin modelling. The regularities of formation and destruction of oil and gas accumulations are summarized by analyzing the fossil and existing oil and gas accumulations, the direction of migration is studied by palaeo‐structural analysis, and the dynamic evolution of Palaeozoic and Mesozoic petroleum systems in southern China is studied according to stages of major tectonic movements. The authors suggest that the realistic exploration targets of Palaeozoic and Mesozoic petroleum systems in southern China are secondary and hydrocarbon‐regeneration petroleum systems, while the existing primary petroleum systems are rare. They propose that the favourable areas for exploration of Palaeozoic and Mesozoic petroleum systems in southern China are the front area of the Daba Mountains and the steep anticlinal zone on the western side of the Shizhu synclinorium in northeastern Sichuan, the Funin‐Yancheng‐Hai'an‐Xinghua‐Baoying area in the northern Jiangsu basin, the Qianjiang‐Xiantao‐Paizhou‐Chacan 1 well area in the southern part of the Chenhu area of the Jianghan basin, the South Poyang basin in Jiangxi and the North subbasin of the Chuxiong basin. This view has been supported by the discovery of the Zhujiadun gas field in the Yancheng subbasin of the northern Jiangsu basin and the Kaixiantaixi oil‐bearing structure in the southern part of the Chenhu area of the Jianghan basin.