bluuebunny/crossref_metadata_2025 huggingface dataset:
Anisotropic Variation Law of Rock Permeability with the Burial Depth of Limestone
Authors: Kaiming TIAN , Li WAN , Jiping TIAN
Published: September 2010

Abstract  Permeability tensors of both macrofracture and microfracture systems were measured progressively along the depth of limestone formations at severed sites. It was found that the principal permeability values Kx, Ky and Kz in these permeability tensors all decrease simultaneously and logarithmically with depth. However, the limestone aquifers are composed of an upper region where the larger permeability ellipsoid is upright or prolate and characterized by KzKx and Kz>Ky, a transitional zone, and a lower zone whose smaller permeability ellipsoid is horizontal or oblate and characterized by Kz<Kx and Kz<Ky. The inversion of the permeability ellipsoids in direction indicates that the anisotropy of rock permeability with the depth of limestone formations has evidently changed. The anisotropic variation law of permeability tensors in a macrofracture system displays a similar pattern with that in a microfracture system. It is next to impossible to examine the rock permeability tensor of the aquifer just by measuring the hydraulic parameters of macrofracture system directly, unless the limestone aquifer is exposed on or near the earth's surface. Therefore, the permeability tensors of a macrofracture system at any depth may be indirectly and roughly determined from the gaugeable permeability tensors of the microfracture system by conversion. This anisotropic variation law of rock permeability with depth is of great significance in the study of three‐dimensional fracture water flow the huge carbonate formations and in the research on the conditions of karst development and karst distribution.
Cephalopods of the “Falang Formation” (Triassic) from Guanling and Zhenfeng Counties, Guizhou Province, China
Authors: Weicheng HAO , Yuanlin SUN , Dayong JIANG , Shouren YANG , Xinping WANG
Published: September 2010

Abstract  The “Falang Formation” of western Guizhou was previously called the “Halobia Bed” and considered to be Ladinian in age. It was subdivided upward into the Zhuganpo, Laishike and Longchang members based on ammonites and the Trachyceras multitubertulatum Zone of the Longchang Member was put in the Lower Carnian. Here in the present paper, 4 genera and 9 species of ammonites and 1 nautiloid genus and species collected from the upper part of the “Falang Formation” (i.e. the Wayao Formation used in this paper, equivalent to the Laishike Member from Guanling and Zhenfeng counties are described. The geological and geographical distribution of these cephalopods, as well as the co‐existing conodonts, put the Wayao Formation to the late early Carnian.
Devonian to Triassic Successions of the Changning‐Menglian Belt, Western Yunnan, China
Authors: Xiaochi JIN , Yizhao WANG , Guanglian XIE
Published: September 2010

Abstract  Phanerozoic strata are distributed in several north‐south trending zones in the central part of the Changning‐Menglian Belt. Four types of Devonian to Triassic stratigraphic successions can be identified: (1) clastics with limestone lenses in the mid‐section, changing up‐section into alternations of fine clastics and cherts; (2) clastics with chert intercalations and limestone lenses, and topped by Permian basic volcanics; (3) clastics‐basic volcanics—carbonates—clastics; and (4) limestones, dolomitic limestones—dark gray thin‐bedded limestones, argillaceous limestones, mudstones and siliceous mudstones. Devonian to Triassic cherts occur in different horizons and different zones from east to west. These cherts are usually transitional to their neighboring clastics. There is no continuous Devonian to Middle Triassic chert sequence in the central zone of the Changning‐Menglian Belt as Liu et al. (1991, 1993) reported. Volcanics and the overlying carbonates described by some workers as “seamount” sequences are more likely to have formed in a marine environment on continental crust. Succession (4) is newly recognized in the area from Menglai to Yong'an in Cangyuan County and further north to Padi of Gengma County. Basalts, cherts and clastics also appear in this area. Mid‐Triassic (very probably Ladinian) radiolarians extracted from bedded cherts in the Ganzhejidi section indicate that they are in higher stratigraphic positions. The change from bedded cherts via siltstones to thick‐bedded sandstones with thin‐bedded fine intercalations in the Ganzhejidi section and (some other outcrops along the road from Cangyuan to Gengma) suggests a fundamental change of sedimentary environment caused by a rapid increase of a large quantity of detritus supply. These siliciclastic sediments are possibly syn‐orogenic deposits.
SHRIMP Age and Geochemistry of the Bikou Volcanic Terrane: Implications for Neoproterozoic Tectonics on the Northern Margin of the Yangtze Craton
Authors: Quanren YAN , Zongqi WANG , HANSON A. D. , DRUSCHKE P. A. , Zhen YAN , Dunyi LIU , Ping JIAN , Biao SONG , Tao WANG , Chunfa JIANG
Published: September 2010

Abstract  The Bikou volcanic terrane is predominated by subalkaline tholeiitic lavas. Rock samples display lower initial ratios of Sr and Nd, 0.701248–0.704413 and 0.511080–0.512341 respectively. 207Pb and 208Pb are significantly enriched in the lavas. Most samples have positive εNd, which indicates that the magma was derived from EM‐type mantle source, while a few samples with negative εNd indicate that there was contamination in the magma evolution. Magma differentiation is demonstrated by variations of LREE and LILE from depletion to enrichment. Additionally, normalized REE patterns and trace elements showed that lavas from the Bikou volcanic terrane have similar characteristics to those of basalts in arc settings caused by subduction and collision. Analyses showed that the Bikou volcanic terrane is a volcanic arc. New evidence proved that the Hengdan Group, north of the Bikou arc, is a turbidite terrane filling a forearc basin. Consequently, the Bikou volcanic terrane and the Hengdan turbidite terrane construct an arc‐basin system. New SHRIMP ages showed that this arc‐basin system developed on the northern margin of the Yangtze craton in the Neoproterozoic (846–776 Ma), and this arc‐basin system is in agreement with the tectonic processes of Rodinia in the Neoproterzoic.
Characteristics of Overpressure Systems and Their Significance in Hydrocarbon Accumulation in the Yinggehai and Qiongdongnan Basins, China
Authors: Xinong XIE , Zhenfeng WANG , Sitian LI , Minqiang ZHANG , Jihai YANG
Published: September 2010

Abstract Overpressure systems are widely developed in the central depression and palco‐uplift in the Yinggehai and Qiongdongnan basins. They can be divided into three types according to the origin of abnormally high formation pressure in the reservoirs, i.e. the autochthonous, vertically‐transmitted and laterally‐transmitted types. The autochthonous overpressure system results from rapid disequilibrium sediment loading and compaction. In the allochthonous overpressure system, the increase of fluid pressure in sandstone originates from the invasion of overpressured fluid flowing vertically or laterally through the conduit units. The autochthonous overpressure system occurs in the deep‐lying strata of Neogene age in the central depression of the Yinggehai and Qiongdongnan basins. The vertically transmitted overpressure system is developed in the shallow strata of Late Miocene and Pliocene ages in the diapiric zone of the central Yinggehai basin, and the laterally transmitted overpressure system occurs in the Oligocene strata of paleo‐uplifts, such as the structure of Ya‐211 in the Qiongdongnan basin. The results indicate that the autochthonous overpressure system is generally a closed one, which is unfavorable for the migration and accumulation of hydrocarbons. In the allochthonous overpressure system, hydrocarbon accumulation depends on the relationship between the formation of overpressure systems and the spatial location and duration of hydrocarbon migration. The interval overlying the overpressure system is usually a favorable hydrocarbon accumulation zone if the duration of fluid expulsion coincides with that of hydrocarbon accumulation.
Analysis of Karst Tufa from Guangxi, China
Authors: FRANčIŠKOVIĆ‐BILINSKI Stanislav , BILINSKI Halka , BARIŠIĆ Delko , HORVATINčIĆ Nada , Daoxian YUAN
Published: September 2010

Abstract The paper presents an analysis of characteristic karst tufa from Guangxi, China, which has not been studied before. A comparison with tufa from Dinaric Karst of Croatia is discussed in view of the C‐type climate. The major mineral is calcite. Minor minerals are quartz and dolomite, depending on location. The content of calcium carbonate varies from 65% to 92%, and that of magnesium carbonate from 0.03% to 1.77%. Among other elements, the most abundant are Fe, from 0.02% to 1.50%, and Ti, from 0.15% to 0.27%. Many other trace elements (V, Cr, Mn, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Hg and Pb) are also present. Specific activity of radionuclides 4 40K, 232Th, 137Cs, 226Ra and 238U varies from sample to sample. Concentration of U in tufa is close to that reported for sedimentary carbonate. Low concentration of 137Cs indicates that this part of the world was not exposed to nuclear explosions. The concentration of 226Ra is the highest in Mashan County. The ratio 238U/226Ra (0.21–0.71) in tufa from Mashan County is significantly lower than the theoretical value of 1. In 5 of the 11 studied samples, stable isotopes δ13C and δ18O were analyzed. They were dated by means of the 14C method. One tufa sample originated in the Pleistocene and the others in the Holocene. Because all of the tufa samples contain traces of Na and K, and K < Na, the tufa from Guangxi belong to the CO2‐outgassing “N” type according to the classification of Liu and He (1994).
The Bulong Gold Deposit—a Quartz‐Barite Vein Type Gold Deposit in Xinjiang: Geological Characteristics and S, He and Ar Isotopic Compositions
Authors: Fuquan YANG , Yitian WANG , Jingwen MAO
Published: September 2010

Abstract  The Bulong gold deposit, located in the southwest Tianshan in China, occurs in the Upper Devonian finegrained clastic rocks. The gold orebodies are controlled by an gently inclined interlayer fractured zone. They are hosted only in quartz‐barite veins though there are barite veins and quartz veins in the ore district. The δ34S values of pyrite in the ores range from 14.6‰ to 19.2‰ and those of barite from 35.0‰ to 39.6‰, indicating that the sulfur was derived from the strata. 3He/4 He ratios of fluid inclusions in pyrite are 0.24–0.82 R/Ra, approximating to that of the crust. The 40Ar/36Ar ratios range from 338 to 471, slightly higher than that of the atmosphere. 40Ar /4He ratios of ore fluids range from 0.015 to 0.412 with a mean of 0.153. Helium and argon isotope compositions of fluid inclusions show that the ore fluids of the Bulong gold deposit were mainly derived from the crust.
40Ar‐39Ar Age of K‐feldspar from K‐feldspar Granite in the Qiaohuote Copper Deposit, Bayanbulak, Xinjiang, and Its Geological Significance
Authors: Zhiliang WANG , Jingwen MAO , Jianmin YANG , Wen CHEN , Zuoheng ZHANG
Published: September 2010

Abstract  By using the 40Ar‐39Ar chronological method to date K‐feldspar from K‐feldspar granite in the Qiaohuote copper district, the authors obtained a plateau age of 274.78±0.44 Ma and an isochron age of 272.7±3.0 Ma. Because there is no tectonic deformation overprinted or hydrothermal alteration in the K‐feldspar granite intrusion after its emplacement, the 40Ar‐39Ar age represents the crystallization age of K‐feldspar in K‐feldspar granite, i.e. the late crystallization age of the K‐feldspar granite intrusion, which indicates that the K‐feldspar granite formed in the intraplate extensional stage during the Early Permian. Moreover, based on the spatial relationship between the K‐feldspar granite intrusion and copper orebodies, variations of copper ore grade, REE characteristics of K‐feldspar granite and copper ores, and H and O isotopic compositions of fluid inclusions in copper ores, the metallogenesis of the Qiaohuote copper deposit is directly related to intrusive activities of the K‐feldspar granite, and thus the crystallization age of K‐feldspar in the granite approximately approaches the metallogenic epoch of the Qiaohuote copper deposit.
40Ar‐39Ar Dating of Albite and Phlogopite from Porphyry Iron Deposits in the Ningwu Basin in East‐Central China and Its Significance
Authors: Jinjie YU , Jingwen MAO
Published: September 2010

Abstract  40Ar‐39Ar dating of albite from the Meishan and Taocun iron deposits yields plateau ages of 122.90±0.16 Ma and 124.89±0.30 Ma, and isochron ages of 122.60±0.16 Ma and 124.90±0.29 Ma, respectively. Phlogopite from the Zhongshan‐Gushan ore field has a plateau age of 126.7±0.17 Ma and an isochron age of 127.21±1.63 Ma. Analysis of regional geodynamic evolution of the middle‐lower Yangtze River region suggests that the porphyry iron deposits were formed as a result of large‐scale lithosphere delamination and strong sinistral strike‐slip movement of the Tancheng‐Lujiang fault zone. The copper, molybdenum and gold deposit system in the middle‐lower Yangtze River region was formed during the stress transition period of the eastern China continent.
Early Paleozoic Magmatism and Gold Mineralization in the Northern Altun, NW China
Authors: Xuanhua CHEN , Xiaofeng WANG , GEHRELS George , Yi YANG , Hong QIN , Zhengle CHEN , Feng YANG , Bailin CHEN , Xuezhi LI
Published: September 2010

Abstract  This paper discusses the relationships between granitic magmatism and gold mineralization and the exhumation history of the Dapinggou gold deposit in northern Altun, NW China based on the geochronological data, including zircon U‐Pb ages, Rb‐Sr isochron age and 40Ar‐39Ar dating and MDD modeling data. The main granitic magmatism age in this area is attained from the ID TIMS U‐Pb geochronology of zircons from the Kuoshibulak granite, the biggest granite in the northern Altun area, which gives a concordant age of 443±5 Ma in the Late Ordovician. Zircon ID TIMS U‐Pb geochronology of the West Dapinggou biotite granite west of the Dapinggou gold deposit gives concordant ages around 485±10 Ma, representing the early stage of Ordovician magmatism. The Rb‐Sr isochron age (487±21 Ma) of 6 quartz inclusion samples from quartz veins in this gold deposit is very close to that of the West Dapinggou granite. MDD modeling of step heating 40Ar‐39Ar data of K‐feldspar from the same West Dapinggou biotite granite gives a rapid cooling history from 300°C to 150°C during 200–185 Ma. According to the age data and the geological setting of this area, we conclude that the Dapinggou gold deposit was formed at the early stage of the Early Paleozoic granitic magmatism in northern Altun, and exhumed in the Early Jurassic due to the normal faulting of the Lapeiquan detachment. The Early Paleozoic magmatism may provide heat source and produce geological fluids, which are very important for gold mineralization. Exhumation in the Mesozoic caused the uplift of the deposit towards the ground surface.
Deep‐water Fan Systems and Petroleum Resources on the Northern Slope of the South China Sea
Authors: Xiong PANG , Shaokun YANG , Ming ZHU , Jinsong LI
Published: September 2010

Abstract  The shallow shelf delta/strand arenaceous‐pelitic deposit region in the north of the Pearl River mouth basin, sitting on the northern continental shelf of the South China Sea, has already become an important oil production base in China. Recent researched has revealed that a great deal of deep‐water fans of great petroleum potentiality exist on the Baiyun deep‐water slope below the big paleo Pearl River and its large delta. Based on a mass of exploration wells and 2‐D seismic data of the shallow shelf region, a interpretation of sequence stratigraphy confirmed the existence of deep‐water fans. The cyclic falling of sea level, abundant detrital matter from the paleo Pearl River and the persistent geothermal subsidence in the Baiyun sag are the three prerequisites for the formation and development of deep‐water fans. There are many in common between the deep‐water shelf depositional system of the northern South China Sea and the exploration hotspots region on the two banks of the Atlantic. For example, both are located on passive continent margins, and persistent secular thermal subsidence and large paleo rivers have supplied abundant material sources and organic matter. More recently, the discovery of the big gas pool on the northern slope of the Baiyun sag confirms that the Lower Tertiary lacustrine facies in the Baiyun sag has a great potentiality of source rocks. The fans overlying the Lower Tertiary source rocks should become the main exploration areas for oil and gas resources.
Pressure Prediction for High‐Temperature and High‐Pressure Formation and Its Application to Drilling in the Northern South China Sea
Authors: Zhenfeng WANG , Xinong XIE
Published: September 2010

Abstract  There are plentiful potential hydrocarbon resources in the Yinggehai and Qiongdongnan basins in the northern South China Sea. However, the special petrol‐geological condition with high formation temperature and pressure greatly blocked hydrocarbon exploration. The conventional means of drills, including methods in the prediction and monitoring of underground strata pressure, can no longer meet the requirements in this area. The China National Offshore Oil Corporation has allocated one well with a designed depth of 3200 m and pressure coefficient of 2.3 in the Yinggehai Basin (called test well in the paper) in order to find gas reservoirs in middle‐deep section in the Miocene Huangliu and Meishan formations at the depth below 3000 m. Therefore, combined with the “863” national high‐tech project, the authors analyzed the distribution of overpressure in the Yinggehai and Qiongdongnan basins, and set up a series of key technologies and methods to predict and monitor formation pressure, and then apply the results to pressure prediction of the test well. Because of the exact pressure prediction before and during drilling, associated procedure design of casing and their allocation in test well has been ensured to be more rational. This well is successfully drilled to the depth of 3485 m (nearly 300 m deeper than the designed depth) under the formation pressure about 2.3 SG (EMW), which indicate that a new step in the technology of drilling in higher temperature and pressure has been reached in the China National Offshore Oil Corporation.
The Classification and Model of Coalbed Methane Reservoirs
Authors: Xianbo SU , Xiaoying LIN , Yan SONG , Mengjun ZHAO
Published: September 2010

Abstract  Coalbed methane has been explored in many basins worldwide for 30 years, and has been developed commercially in some of the basins. Many researchers have described the characteristics of coalbed methane geology and technology systematically. According to these investigations, a coalbed methane reservoir can be defined: “a coal seam that contains some coalbed methane and is isolated from other fluid units is called a coalbed methane reservoir”. On the basis of anatomization, analysis, and comparison of the typical coalbed methane reservoirs, coalbed methane reservoirs can be divided into two classes: the hydrodynamic sealing coalbed methane reservoirs and the self‐sealing coalbed methane reservoirs. The former can be further divided into two sub‐classes: the hydrodynamic capping coalbed methane reservoirs, which can be divided into five types and the hydrodynamic driving coalbed methane reservoirs, which can be divided into three types. The latter can be divided into three types. Currently, hydrodynamic sealing reservoirs are the main target for coalbed methane exploration and development; self‐sealing reservoirs are unsuitable for coalbed methane exploration and development, but they are closely related with coal mine gas hazards. Finally, a model for hydrodynamic sealing coalbed methane reservoirs is established.
Coalbed Methane‐bearing Characteristics and Reservoir Physical Properties of Principal Target Areas in North China
Authors: Shuheng TANG , Shenglin SUN , Duohu HAO , Dazhen TANG
Published: September 2010

Abstract  The coalbed methane (CBM) resources in North China amounts up to 60% of total resources in China. North China is the most important CBM accumulation area in China. The coal beds of the Upper Paleozoic Taiyuan and Shanxi formations have a stable distribution. The coal reservoir of target areas such as Jincheng, Yanquan‐Shouyang, Hancheng, Liulin, etc. have good CBM‐bearing characteristics, high permeability and appropriate reservoir pressure, and these areas are the preferred target areas of CBM developing in China. The coal reservoirs of Wupu, Sanjiaobei, Lu'an, Xinmi, Anyang‐Hebi, Jiaozuo, Xinggong and Huainan also have as good CBM‐bearing characteristics, but the physical properties of coal reservoirs vary observably. So, further work should be taken to search for districts with high pressure, high permeability and good CBM‐bearing characteristics. Crustal stresses have severe influence on the permeability of coal reservoirs in North China. From west to east, the crustal stress gradient increases, while the coal reservoirs permeability decreases.
Paleogene and Early Neogene Lacustrine Reefs in the Western Qaidam Basin, China
Authors: Jianhua ZHONG , Zhifeng WEN , Zeqing GUO , Haiqiao WANG , Jianbo GAO
Published: September 2010

Abstract Typical reefs in the Paleogene and early Neogene strata of the Qaidam Basin, Tibetan Plateau, China, reveal their internal structures and sedimentation environments and consist mainly of algal reef, stromatolite reef and thrombolite reef with distinct øeef structures, fore‐reef, back‐reef and reef‐plateau. The fore‐reef is characterized by a combination of pinnacle reef, thrombolite and algal reef. The back reef is composed of stromatolite reef and algal reef. The pinnacle reefs (micro‐atoll), most of which are several tens of centimeters in diameter (whereas some exceptionally big ones are over 200 cm in diameter), and several tens of centimeter to 2 m in height, are situated on the far front‐edge of the reef; the pinnacle reef is also often of recumbent form with a gravel‐filled circular hole in the center. The algal reef is in the form of dome and irregular beds, and filled with algal detritus, ostracodes, spirorbis fossils, ooid and terrigenous debris, and worm traces; cavities and scour marks are often developed. The algal reef is gray commonly when fresh and weathers to a brown color. The lacustrine thrombolite in the Qaidam Basin is light gray or deep gray when fresh, white‐gray or brown when weathered, dense and homogeneous with abundant pores filled by oil and bitumen. Observed under the microscope, the thrombolite consists mainly of brown or brown‐black clots with a little algal debris, ooid, pellet, ostracodes, spirorbis fossils and terrigenous debris, in some cases, terrigenous debris, even gravel, is abundant. Many features of the thrombolite suggest that it is formed in a high‐energy environment. The stromatolite reefs developed on the lacustrine algal reef in the Qaidam Basin are very complex whether in shape or in internal structure. The simplest ones form laminated layers and the most complex ones have intensely branching structures. The size is also variable.
Accumulation Conditions of Organic Matter during the Deposition of Black Shales of the Buxin Formation (Early Paleogene) in the Sanshui Basin, South China
Authors: Chunlian LIU , OSCHMANN Wolfgang , Yan BAI , Yixin DONG , Yecai XIE
Published: September 2010

Abstract  Analyses of organic carbon, nitrogen, sulfur and iron have been performed in order to understand sources and preservation of organic matter in black shale of the Buxin Formation (Early Paleogene) from the Sanshui Basin. The C/N ratios show that the organic matter is characterized by a mixture of terrestrial and phytoplanktonic contributions. The relative importance of different sources depend on climate conditions and most of organic matter is of terrestrial origin. The relationships between C, S and Fe indicate that the brackish environment with alternation of anoxia and low‐O2 developed in the bottom waters during the deposition of these organic‐rich sediments as a result of a mixed setting of thermal stratification and salinity stratification, the latter being the consequence of intermittent sea water incursion. Bacterial sulfate reduction is the most effective early diagenesis affecting the preservation of organic matter. The intensity of sulfate reduction is related to the relative proportion of metabolizable organic matter supplied to sediments.
Potential Hazards of Eruptions around the Tianchi Caldera Lake, China
Authors: Haiquan WEI , Hanjing HONG , SPARKS R.S.J. , WALDER J.S. , Bin HAN
Published: September 2010

Abstract  Since the eruption of the Tianchi volcano about 1000 years ago, there have been at least 3 to 5 eruptions of small to moderate size. In addition, hazardous avalanches, rock falls and debris flows have occurred during periods between eruptions. A future eruption of the Tianchi volcano is likely to involve explosive interaction between magma and the caldera lake. The volume of erupted magma is almost in a range of 0.1–0.5 km3. Tephra fallout may damage agriculture in a large area near the volcano. If only 1% of the lake water were ejected during an eruption and then precipitated over an area of 200 km2, the average rainfall would be 100 mm. Moreover, lahars are likely to occur as both tephra and water ejected from the caldera lake fall onto flanks of the volcano. Rocks avalanching into the caldera lake also would bring about grave hazards because seiches would be triggered and lake water with the volume equal to that of the landslide would spill out of the existing breach in the caldera and cause flooding downstream.
Effects of Overpressured Fluid Flow on Petroleum Accumulation in the Yinggehai Basin
Authors: Fang HAO , Weiliang DONG , Huayao ZOU , Jianqun JIANG
Published: September 2010

Abstract  The Yinggehai Basin is a strongly overpressured Cenozoic basin developed in the northern continental shelf of the South China Sea. The flow of overpressured fluids in this basin has given rise to strong effects on petroleum accumulation. (1) The overpressured fluid flow has enhanced the maturation of shallow‐buried source rocks, which has caused the source rocks that would have remained immature under the conduction background to be mature for hydrocarbon generation. As a result, the overpressured fluid flow has increased the volume and interval of mature source rocks. (2) The overpressured fluid flow has strong extraction effects on the immature or low‐mature source rocks in the shallow parts. This has increased, to some extent, the expulsion efficiency of the source rocks. More importantly, the extraction effects have strongly limited the effectiveness of biomarker parameters from oil and condensate in reflecting the source and maturity of the oil and gas. (3) The flow has caused the sandstones in the shallow parts to get into the late diagenesis stage, and significantly reduced the porosity and permeability of the sandstones. This study confirms that even in sedimentary basins in which no topography‐driven groundwater flow systems have ever developed, the cross‐formation migration of overpressured fluids and the resultant energy conduction and material exchange can significantly affect the thermal regime, source rock maturation and sandstone diagenesis. As a result, the effects of overpressured fluid flow must be taken into account in analyzing the mechanism of petroleum accumulation.
Enantiornithine Bird with Diapsidian Skull and Its Dental Development in the Early Cretaceous in Liaoning, China
Authors: Enpu GONG , Lianhai HOU , Lixia WANG
Published: September 2010

Abstract A large number of enantiornithine birds are discovered from the Early Cretaceous Jiufutang Formation in western Liaoning, China. They are all small‐sized birds with a few small teeth. The enantiornithine bird from the Jiufutang Formation in the Shangheshou area, Chaoyang, Liaoning Province reported in this paper is the largest individual known in all enantiornithine birds of the Early Cretaceous. However, its teeth possess a feature of pseudoheterodont. Some different development stages of the new teeth substitute the earlier stages and the stages of development are preserved in this specimen. This development pattern is similar to that of Archaeopteryx and alligator but not dinosaur. A well‐developed postorbital was also preserved in the skull, which was a diapsidian skull like that of Confuciusornis. Additionally, the distinctive preservation of its prefrontal distinguishes it from other enantiornithine birds of the Early Cretaceous.
Sequence of the Cenozoic Mammalian Faunas of the Linxia Basin in Gansu, China
Authors: Tao DENG , Xiaoming WANG , Xijun NI , Liping LIU
Published: September 2010

Abstract In the Linxia Basin on the northeast margin of the Tibetan Plateau, the Cenozoic strata are very thick and well exposed. Abundant mammalian fossils are discovered in the deposits from the Late Oligocene to the Early Pleistocene. The Dzungariotherium fauna comes from the sandstones of the Jiaozigou Formation, including many representative Late Oligocene taxa. The Platybelodon fauna comes from the sandstones of the Dongxiang Formation and the conglomerates of the Laogou Formation, and its fossils are typical Middle Miocene forms, such as Hemicyon, Amphicyon, Platybelodon, Choerolophodon, Anchitherium, and Hispanotherium. The Hipparion fauna comes from the red clay of the Liushu and Hewangjia Formations, and its fossils can be distinctly divided into four levels, including three Late Miocene levels and one Early Pliocene level. In the Linxia Basin, the Hipparion fauna has the richest mammalian fossils. The Equus fauna comes from the Wucheng Loess, and it is slightly older than that of the classical Early Pleistocene Nihewan Fauna. The mammalian faunas from the Linxia Basin provide the reliable evidence to divide the Cenozoic strata of this basin and correlate them with European mammalian sequence.
Origin, Age and Significance of Pseudotachylites from the Eastern Dabieshan Orogenic Belt, China
Authors: Jianmin LIU , Shuwen DONG , Jiasheng ZHANG , Xiaochun LIU , Bailin CHEN
Published: September 2010

Abstract Recent field survey in the eastern Dabieshan Mountains has revealed extensive occurrences of pseudotachylite. The pseudotachylite tends to occur as simple veins and injected networks along the NE‐SW‐trending fracture zones or shear zones, which are parallel to the Tanlu fault zone and cut all the pre‐Cretaceous geological bodies. The characteristics of both the microstructures gained by the optical microscope and SEM imaging and the geochemistry between the pseudotachylites and their host rocks show that the pseudotachylites were formed mainly by ultracataclasis of their wall rocks in which they occur. The bulk K‐Ar ages of the pseudotachylites yielded a narrow range of 81–93 Ma, and moreover the laser‐probe 40Ar/39Ar dating of phengite overprinting on the pseudotachylite gave a weighted mean age of 78.9 Ma. These results show that the pseudotachylites from the eastern Dabieshan Mountains formed along the NE‐SW‐trending fault zone during the uplifting of the orogenic belt at 80–90 Ma, which places important constrains on the cooling and exhumation history of the Dabieshan Mountains during and after the late Cretaceous.
SHRIMP Dating and Recrystallization of Metamorphic Zircons from a Granitic Gneiss in the Sulu UHP Terrane
Authors: Hongyan LI
Published: September 2010

Abstract An unusual zircon SHRIMP dating result of a granitic gneiss from the Qinglongshan eclogite‐gneiss roadcut section is presented in this paper. The very peculiar and complicated internal structures, as well as the very low Th/U ratios (0.01–0.08) of the zircons indicate that they were formed by metamorphic recrystallization. Strongly in contrast with previously published zircon U‐Pb ages of the Dabie‐Sulu UHP metamorphic rocks where protolith ages of 600–800 Ma are commonly recorded, only metamorphic age of 218±5 Ma, defined by 18 analytical spots either in rim or in core of zircons, are recorded in this granitic gneiss. This age represents the time of the complete metamorphic recrystallization overprint on primary magmatic zircons. The recrystallization was derived by the UHP metamorphism, and was strengthened by the early stage of retrograde metamorphic fluid activity.
The Archipelagic Ocean System of the Eastern Eurasian Tethys
Authors: Hongfu YIN , Kexin ZHANG , Qinglai FENG
Published: September 2010

Abstract Unlike typical oceans such as the wide and “clean” Atlantic, the Tethys has been showing an archipelagic pattern during all its evolutionary stages. Compared with the traditional, wedge‐shaped and relatively “clean” ocean model, the archipelagic model is more suitable for the Tethys, especially the eastern Tethys. This paper demonstrates the eastern Tethys archipelagic system in terms of the subdivision, characteristics and evolutionary history of the Qinling‐Qilian‐Kunlun, South China and Xizang (Tibet)‐Yunnan Regions of the eastern Eurasian Tethys.
The Sequence of Magmatic‐Tectonic Events and Orogenic Processes of the Yanshan Belt, North China
Authors: Jinfu DENG , Shangguo SU , Xuanxue MO , Guochun ZHAO , Qinghiu XIAO , Guangyi JI , Ruizhao QIU , Hailing ZHAO , Zhaohua LUO , Yang WANG , Cui LIU
Published: September 2010

Abstract This paper emphasizes that the interactive constraints of geology and isotopic dating is the best approach to construct the geological event sequence, and has compiled 106 data of reasonable isotopic ages for the igneous rocks of the Yanshan belt. We propose a sequence of mgmatic‐tectonic events in the Jurassic‐Cretaceous Yanshan orogen of North China. Five orogenic episodes are divided, (1) pre‐and initial orogenic episode (Early Jurassic); (2) early orogenic episode (Middle Jurassic); (3) peak orogenic episode (Late Jurassic); (4) late orogenic episode (early Early Cretaceous), and (5) post‐orogenic episode. Each episode is a short cycle, all of the orogenic processes construct a longer cycle, and they, in general, followed a counter‐clockwise (ccw) PTt path. Finally, it is suggested that the Yanshanian movement was so intensive that the magmatism and tectonic deformation had involved all the lithosphere thickness and the late‐Achaean‐formed cratonic lithosphere had been significantly reworked.
Nd‐Sr Isotopic Geochemistry of the Late Archean‐Paleoproterozoic Granitoids in the Lüliang‐Wutai Terrain, North China Craton, and Implications for Petrogenesis
Authors: Bin CHEN , Shuwen LIU , Rui WANG , Zhichao CHEN , Chaoqun LIU
Published: September 2010

Abstract: In this paper we report geochemical and Nd‐Sr isotopic data for a late Archean gneissic granitic pluton (Hengling pluton), an early Paleoproterozoic complex (Xipan complex) and a late Paleoproterozoic granitic pluton (Yunzhongshan granites) from the Lüliang‐Wutai terrain, North China, to trace the source of these late Archean‐Paleoproterozoic granitoids and, particularly, to understand the nature and mechanism of continental growth at that time. The Hengling granitic gneisses (ca. 2.51 Ga) are characterized by high Na2O and LILEs, TTG‐like REE patterns (highly depleted HREE and minor Eu anomalies) and moderately depleted Nd‐Sr isotopic compositions (∍Nd(t) =1.2‐2.7, ISr=0.7015‐0.7019), and were considered as being products of arc magmatism that was developed upon the North China craton. The Xipan complex (ca. 2.2 Ga) contain gabbroic diorite and monzonite, mostly being Na2O‐rich, highly fractionated REE patterns and isotopically enriched (∍Nd(t) =−1.5 to −4.1, ISr=0.7038‐0.706). The gabbroic diorites probably originated from melting of an enriched mantle source, but significantly contaminated by lower crustal material, and the monzonites probably represent a product of a mixture between the gabbroic dioritic magma and granitic melts of crustal origin. The Yunzhongshan post‐collisional granitoids (ca. 1.8 Ga) are characterized by high‐K affinity and highly‐enriched and homogeneous Nd isotopic compositions (∍Nd(t) = −4.9 to −5.7), although they split into two groups in terms of REE patterns: one group showing elevated HREE (and Sc, Y and Zr) with significant negative Eu anomalies and the other showing highly depleted HREE and, to a lesser extent, mid‐REE with negligible Eu anomalies. These granites are genetically related to a process of extensional collapse of a thickened orogen. They formed through magma mixing between mantle‐derived basaltic magmas and crust‐derived granitic melts, followed by significant fractionation of ferromagnesian phases (like hornblende and Cpx) and feldspar and accessory zircons. Some Yunzhongshan granites show very old Nd model ages (2.9‐3.0 Ga), suggesting the existence of continental crust older than 2.7 Ga, which is supported by our zircon Hf isotopic data for these granites.
Features and Formation Mechanism of Faults and Potash‐forming Effect in the Lop Nur Salt Lake, Xinjiang, China
Authors: Chenglin LIU , Mili WANG , Pengcheng JIAO , Shude LI , Yongzhi CHEN
Published: September 2010

Abstract: The Lop Nur Salt Lake, located in the eastern part of the Tarim Basin, Xinjiang, China, has become a playa in the Quaternary. Rhombic in shape, the Lop Nur depression is mainly controlled by the NE‐striking and nearly N‐S‐striking sets of faults. Since 1995, a superlarge brine potash deposit with potash resources of 2.50times108t has been found in the Luobei subbasin in the northeastern part of the Lop Nur. We intensively studied the features and formation mechanism of faults inside the Lop Nur through satellite images, geomorphologic survey and continuous conductivity imaging and found seven subparallel graben faults formed under the action of nearly N 10° E principal compressional stress during deposition of the Lop Nur Salt Lake. These faults are up to >60 km long and 1–4 km wide and may extend downward for 1000 m or more. It is just under the action of these tensional faults that potash subbasins formed. The largest subbasin is the Luobei subbasin and the smaller ones are the Luoxi hollow, Erbei hollow and Tienan hollow. Investigation also indicates that the graben faults in the Lop Nur not only control the origin of the potash subbasins, but they themselves are also good brine reservoir structures, in which abundant potash‐rich brines are stored. Therefore, The faults had played an important role in the potash formation of the Lop Nur.
Acid Mine Drainage and Heavy Metal Pollution from Solid Waste in the Tongling Mines, China
Authors: Xiaochun XU , Qiaoqin XIE , Fang CHEN , Jun WANG , Wentao WU
Published: September 2010

Abstract: Based on investigation of the characteristics of solid waste of two different mines, the Fenghuangshan copper mine and the Xinqiao pyrite mine in Tongling, Anhui province in central‐east China, the possibility and the differences of acid mine drainage (AMD) of the tailings and the waste rocks are discussed, and the modes of occurrence of heavy metal elements in the mine solid waste are also studied. The Fenghuangshan copper mine hardly produces AMD, whereas the Xinqiao pyrite mine does and there are also differences in the modes of occurrence of heavy metal elements in the tailings. For the former, toxic heavy metals such as Cu, Pb, Zn, Cd, As and Hg exist mostly in the slag mode, as compared to the latter, where the deoxidization mode has a much higher content, indicating that large amounts minerals in the waste rocks have begun to oxidize at the earth surface. AMD is proved to promote the migration and spread of the heavy metals in mining waste rocks and lead to environmental pollution of the surroundings of the mine area.
Formation Dynamics and Quantitative Prediction of Hydrocarbons of the Superpressure System in the Dongying Sag
Authors: Fenggui SUI , Xuefeng HAO , Qing LIU , Qin'gong ZHUO , Shouchun ZHANG
Published: September 2010

Abstract: Based on the theory of formation dynamics of oil/gas pools, the Dongying sag can be divided into three dynamic systems regarding the accumulation of oil and gas: the superpressure closed system, the semi‐closed system and the normal pressure open system. Based on the analysis of genesis of superpressure in the superpressure closed system and the rule of hydrocarbon expulsion, it is found that hydrocarbon generation is related to superpressure, which is the main driving factor of hydrocarbon migration. Micro fractures formed by superpressure are the main channels for hydrocarbon migration. There are three dynamic patterns for hydrocarbon expulsion: free water drainage, hydrocarbon accumulation and drainage through micro fissures. In the superpressure closed system, the oil‐driving‐water process and oil/gas accumulation were completed in lithologic traps by way of such two dynamic patterns as episodic evolution of superpressure systems and episodic pressure release of faults. The oil‐bearing capacity of lithologic traps is intimately related to reservoir‐forming dynamic force. Quantitative evaluation of dynamic conditions for pool formation can effectively predict the oil‐bearing capability of traps.
Determining the Main Gas‐generation Phase of Marine Organic Matters in Different Occurrence States using the Kinetic Method
Authors: Yunpeng WANG , Changyi ZHAO , Zhaoyun WANG , Hongjun WANG , Yanrong ZOU , Jinzhong LIU , Wenzhi ZHAO , Dehan LIU , Jialan LU
Published: September 2010

Abstract: This paper probes the determination of the main gas‐generation phase of marine organic mattes using the kinetic method. The main gas‐generation phase of marine organic matters was determined by coupling the gas generation yields and rates in geological history computed by the acquired kinetic parameters of typical marine organic matters (reservoir oil, residual bitumen, low‐maturity kerogen and residual kerogen) in both China and abroad and maturity by the EasyRo(%) method. Here, the main gas‐generation phase was determined as Ro%=1.4%–2.4% for type I kerogen, Ro%=1.5–3.0% for low‐maturity type II kerogen, Ro%=1.4–2.8% for residual kerogen, Ro%=1.5–3.2% for residual bitumen and Ro%=1.6–3.2% for reservoir oil cracking. The influences on the main gas‐generation phase from the openness of the simulated system and the “dead line” of natural gas generation are also discussed. The results indicate that the openness of simulation system has a definite influence on computing the main gas‐generation phase. The main gas‐generation phase of type II kerogen is Ro%=1.4–3.1% in an open system, which is earlier than that in a closed system. According to our results, the “dead line” of natural gas generation is determined as Ro=3.5% for type I kerogen, Ro=4.4–4.5% for type II kerogen and Ro=4.6% for marine oil. Preliminary applications are presented taking the southwestern Tarim Basin as an example.
Early Uplift History of the Tibetan Plateau: Records from Paleocurrents and Paleodrainage in the Hoh Xil Basin
Authors: Haisheng YI , Chengshan WANG , Zhiqiang SHI , Jinhui LIN , Lidong ZHU
Published: September 2010

Abstract: Paleocurrent indicator data collected in field work were used to study the early Cenozoic regional paleodrainage patterns in the Hoh Xil basin in northern Tibetan plateau. The paleocurrent directions of the Eocene Fenghuoshan Group obviously show that the flows were northward with a unidirectional dispersal pattern. This probably reflects the uplift of the Qiangtang terrain during the initial basin deposition period and indicates that the Tanggula Moutains occurred as topographic highlands at least in the Eocene. Paleoflows of the Oligocene Yaxicuo Group were dominantly oriented to the north and then flowed eastwards during its late deposition. This regional variability of paleodrainage patterns of the Yaxicuo Group is interpreted to record the dispersal style of sediments from transverse rivers to longitudinal river systems. It is inferred that the Oligocene uplift of the Kunlun Mountains obstructed by northward paleoflows and created longitudinal river systems parallel to the orogenic belts. The temporal and spatial changes of the paleodrainage patterns suggest that the northern boundary of the Tibetan plateau during the early Cenozoic was situated in the Hoh Xil area and its uplift has progressed northwards through time.
Annelid from the Neoproterozoic Doushantuo Formation in Northeastern Guizhou, China
Authors: Yue WANG , Xunlian WANG
Published: September 2010

Abstract: Wenghuiia jiangkouensis gen. et sp. nov., characterized by modern annelid taxonomy in morphology and functional biology, is found in black carbonaceous shale from the Neoproterozoic Ediacaran Doushantuo Formation (about 555 Ma) near Wenghui, Jiangkou, northeastern Guizhou Province. The elongate, cylindrical body is composed of many homologous metameres with a true coelom and coelomic pouches. The mouth is at the front of the first segment and the anus at the end of body. A long 11th or 12th segment is probably functionally for procreation, being a clitellum. There are parapodia on the venter of the segments from the rear of the second segment to the front of the clitellum. The setae on all metameres, on the parapodia, and around the anus, differ. In the centre of body, a line probably represents the alimentary canal passing through the body from mouth to anus. A closed vascular system consists of a dorsal vessel at least. W. jiankouensis might represent the oldest discovered ‘modern’ annelid but it is not a primitive type. It lived on the depositional surface of a shallow sea with an environment of calm‐water and abundant light.
The Most Complete Pistosauroid Skeleton from the Triassic of Yunnan, China
Authors: Lijun ZHAO , SATO Tamaki , Chun LI
Published: September 2010

Abstract: A new specimen discovered from the Falang Formation in northeastern Yunnan represents the most complete skeleton of Triassic pistosauroids. The new specimen is referred to Yunguisaurus Cheng et al., 2006 on the basis of the skull features, such as the presence of a separated nasal entering the external naris, a large pineal foramen located at the frontal/parietal suture and an interpterygoid vacuity with a narrow anterior extension. The new specimen differs from the type species of Yunguisaurus liae Cheng et al., 2006 in some aspects. Most of these differences can be attributed to ontogenetic variations. The new specimen is provisionally considered as Yunguisaurus cf. liae although its relatively short snout of the skull and slenderer hyoid may not be explained ontogenetically. Whether or not the new specimen represents a different taxon has to wait for a detailed study of the whole skeleton.