bluuebunny/crossref_metadata_2025 huggingface dataset:
Cascaded Evolution of Mantle Plumes and Metallogenesis of Core‐ and Mantle‐derived Elements
Authors: Shuyin NIU , Quanlin HOU , Zengqian HOU , Aiqun SUN , Baode WANG , Hongyang LI , Chuanshi XU
Published: September 2010

Abstract  Mineral deposits are unevenly distributed in the Earth's crust, which is closely related to the formation and evolution of the Earth. In the early history of the Earth, controlled by the gravitational contraction and thermal expansion, lighter elements, such as radioactive, halogen‐family, rare and rare earth elements and alkali metals, migrated upwards; whereas heavier elements, such as iron‐family and platinum‐family elements, base metals and noble metals, had a tendency of sinking to the Earth's core, so that the elements iron, nickel, gold and silver are mainly concentrated in the Earth's core. However, during the formation of the stratified structure of the Earth, the existence of temperature, pressure and viscosity differences inside and outside the Earth resulted in vertical material movement manifested mainly by cascaded evolution of mantle plumes in the Earth. The stratifications and vertical movement of the Earth were interdependent and constituted the motive force of the mantle‐core movement. The cascaded evolution of mantle plumes opens the passageways for the migration of deep‐seated ore‐forming material, and thus elements such as gold and silver concentrated in the core and on the core‐mantle boundary migrate as the gaseous state together with the hot material flow of mantle plumes against the gravitational force through the passageways to the lithosphere, then migrate as the mixed gas‐liquid state to the near‐surface level and finally are concentrated in favorable structural expansion zones, forming mineral deposits. This is possibly the important metallogenic mechanism for gold, silver, lead, zinc, copper and other many elements. Take for example the NE‐plunging crown of the Fuping mantle‐branch structure, the paper analyzes ductile‐brittle shear zone‐type gold fields (Weijiayu) at the core of the magmatic‐metamorphic complex, principal detachment‐type gold fields (Shangmingyu) and hanging‐wall cover fissure‐vein‐type lead‐zinc polymetallic ore fields (Lianbaling) and further briefly analyzes the source of ore‐forming material and constructs an ore‐forming and ‐controlling model.
Kalligrammatid Lacewings from the Upper Jurassic Daohugou Formation in Inner Mongolia, China
Authors: Junfeng ZHANG
Published: September 2010

Abstract A new species, referable to a new genus, is erected, and named the Sinokalligramma jurassicum gen. et sp. nov. It is the second finding of kalligrammatids in the Daohugou Formation. The origin and migration of the family Kalligrammatidae are discussed. The geological age and stratigraphic correlation of the Daohugou and Karabastau Formations are briefly reviewed and reassessed.
First Occurrence of Mandarinoite in China
Authors: BELKIN Harvey E. , Baoshan ZHENG , Jianming ZHU
Published: September 2010

Abstract This report describes the first occurrence of the rare mineral mandarinoite (Fe3+2Se3O9 · 6H2O) in China. It occurs in the Lower Permian Maokou Formation carbonaceous shale in Yutangba Village east of Enshi City in southwestern Hubei Province. The shale is selenium‐rich and contains native selenium, V‐Mo‐Cr‐bearing iron oxide, clay and quartz. Weathering of the selenium in the bedrock under moderate to high redox conditions in the presence of ferric iron has formed mandarinoite.
Isotopic Ages of the Carbonatitic Volcanic Rocks in the Kunyang Rift Zone in Central Yunnan, China
Authors: Yongbei ZHANG , Guilan WANG , Jianfeng NIE , Chongshun ZHAO , Chengyan XU , Jiaxiang QIU , Hao Wang
Published: September 2010

Abstract The Mesoproterozoic Kunyang rift, which is located on the western margin of the Yangtze platform and the southern section of the Kangdian axis, is a rare massive Precambrian iron‐copper polymetallic mineralization zone in China. The Mesoproterozoic Wulu (Wuding‐Lufeng) basin in the middle of the rift is an elliptic basin controlled by a ring fracture system. Moreover, volcanic activities in the basin display zonation of an outer ring, a middle ring and an inner ring with carbonatitic volcanic rocks and sub‐volcanic dykes discovered in the outer and middle rings. The Sm‐Nd isochron ages have been determined for the outer‐ring carbonatitic lavas (1685 Ma) and basaltic porphyrite of the radiating dyke swarm (1645 Ma) and the Rb‐Sr isochron ages for the out‐ring carbonatitic lavas (893 Ma) and the middle‐ring dykes (1048 Ma). In combination of the U‐Pb concordant ages of zircon (1743 Ma) in trachy‐andesite of the corresponding period and stratum (1569 Ma) of the Etouchang Formation, as well as the Rb‐Sr isochron age (1024 Ma) and K‐Ar age (1186 Ma) of the dykes in the middle ring, the age of carbonatites in the basin is preliminarily determined. It is ensured that all of these carbonatites were formed in the Mesoproterozoic period, whereby two stages could be identified as follows: in the first stage, carbonatitic volcanic groups, such as lavas, pyroclastic rocks and volcaniclastic sedimentary rocks, were formed in the outer ring; in the second stage, carbonatitic breccias and dykes appeared in the middle ring. The metamorphic age of the carbonatitic lavas in the outer ring was determined to be concurrent with the end of the first stage of the Neoproterozoic period, corresponding to the Jinning movement in central Yunnan.
Gold Content of Mantle‐Derived Rocks from Eastern China and Its Implications
Authors: Ying HE , Zhenxin DONG , Kefen YUE , Zhanjun ZHANG , Xin WANG
Published: September 2010

Abstract We have analyzed the gold content of 65 samples of mantle‐derived xenoliths and their host rocks from eastern China, which is found to be inhomogeneous, falling in the ranges of 1.0times10−9‐8.2times10−9 (averaging 3.8 times 10‐9) and 0.2times10−9‐5.3times10−9 (averaging 2.7times10−9) in the mantle‐derived xenoliths and the host basalts respectively. Except the samples from Wanquan County of Hebei Province and Anding County of Hainan Province, the gold content is the highest on the margins of the North China platform and decreases spatially towards the north and south, and temporally the samples of the Tertiary have a higher gold content than those of the Quaternary. The gold content of the mantle‐derived xenoliths and the host Paleozoic kimberlites is 3.8times10−9‐180times10−9 and 0.1times10−9‐38.0times10−9 respectively, which are higher than that in the mantle‐derived xenoliths in basalt and the host Cenozoic basalts. The mantle‐derived xenoliths have a higher gold content than the host rocks, but their relativity is not very clear, suggesting that the genetic relationship between them is complex. Our data indicate that the average gold content of the lithospheric mantle in eastern China is approximately equal to or approaching 3.8times10−9, which is lower than the average abundance of the upper mantle (5.0times10−9), higher than the average abundance of the continental crust (3.0times10−9) and only slightly higher than the average abundance of the lower continental crust (3.4times10−9). Except the samples from Hainan Province, the mantle‐derived xenoliths in basalts with a high gold content are distributed on the two margins of the North China platform, corresponding to the gold deposits‐concentrated districts in northwest Hebei Province and Shandong Province, showing the control by the old continental lithospheric mantle and the lower continental crust on the margins of the North China platform. The gold content of the mantle‐derived xenoliths from Hainan Province ranges from 7.1times10−9 to 15times10−9, suggesting that some blocks of the lithospheric mantle in Hainan Province may be derived from the ancient gold‐rich lithospheric mantle of western Australia and that Hainan Province may possibly be an important gold deposits‐concentrated district. Some mantle‐derived xenoliths in kimberlite of Shandong Province have an excessively high gold content amounting to 180times10−9, which provides new evidence for the possibility of “finding gold deposits near kimberlite pipes or alkali‐basalt volcanic vents”. Thererfore, the gold content of the mantle‐derived xenoliths may be an indicator to the distribution of gold deposits‐concentrated districts.
The Junggar Immature Continental Crust Province and Its Mineralization
Authors: Jingbin WANG , Yuwang WANG , Lijuan WANG
Published: September 2010

Abstract  According to the study on the peripheral orogenic belts of the Junggar basin and combined with the interpretation of geophysical data, this paper points out that there is an Early Paleozoic basement of immature continental crust in the Junggar area, which is mainly composed of Neoproterozoic‐Ordovician oceanic crust and weakly metamorphosed covering sedimentary rocks. The Late Paleozoic tectonism and mineralization were developed on the basement of the Early Paleozoic immature continental crust. The Junggar metallogenic province is dominated by Cr, Cu, Ni and Au mineralization. Those large and medium‐scale deposits are mainly distributed along the deep faults and particularly near the ophiolitic mélange zones, and formed in the Late Paleozoic with the peak of mineralization occurring in the Carboniferous‐Permian post‐collisional stage. The intrusions related to Cu, Ni and Au mineralization generally have low Isr and positive ɛENd(t) values. The δ34S values of the ore deposits are mostly near zero, and the lead isotopes are mostly of normal lead. All these indicate that the ore‐forming material comes either directly from the mantle‐derived magma (for chromite and Cu‐Ni deposits) or from recirculation of the basement material of the Early Paleozoic immature crust (for most Cu and Au deposits).
Ore‐forming Conditions and Prospecting in the West Kunlun Area, Xinjiang, China
Authors: Yongguan DONG , Kunyi GUO , Huiliang XIAO , Chuanlin ZHANG , Yu ZHAO
Published: September 2010

Abstract  The West Kunlun ore‐forming belt is located between the northwestern Qinghai‐Tibet Plateau and southwestern Tarim Basin. It situated between the Paleo‐Asian Tectonic Domain and Tethyan Tectonic Domain. It is an important component of the giant tectonic belt in central China (the Kunlun‐Qilian‐Qinling Tectonic Belt or the Central Orogenic Belt). Many known ore‐forming belts such as the Kunlun‐Qilian Qinling ore‐forming zone, Sanjiang (or Three‐river) ore‐forming zone, Central Asian ore‐forming zone, etc. pass through the West Kunlun area. Three ore‐forming zones and seven ore‐forming subzones were classified, and eighteen mineralization areas were marked. It is indicated that the West Kunlun area is one of the most favorable region for finding out large and superlarge ore deposits.
Ore‐Bearing Formations of the Precambrian in South China and Their Prospects
Authors: Jurui HE , Aiguo WANG , Xingjian RUI , Chunhai LI
Published: September 2010

Abstract  In the Precambrian System of the Yangtze and Cathaysian plates six ore‐bearing formations can be identified: the Cu‐Pb‐Zn‐bearing formations in volcanic rocks of marine facies of the Neoarchean‐Paleoproterozoic, Cu‐Au‐bearing formations and Pb‐Zn‐bearing formations in volcanic rocks of marine facies of the Mesoproterozoic, Pb‐Zn‐bearing formations in volcaniclastic rock and carbonate rock of the Neoproterozoic, Fe‐Mn‐bearing formations in the volcaniclastic rock of the Neoproterozoic, and Ni‐Cr‐serpentine‐bearing formations in ophiolite and ultrabasic rock of the Meso‐ and Neoproterozoic. They were mostly formed in the marginal rift valleys of the Yangtze and Cathaysian plates, where occur stratabound and stratiform ore deposits, thermal deposits and porphyry polymetallic deposits. The six regions with ore‐bearing formations have good prospects for ore deposits.
Geochemical Trace of Silicon Isotopes of Intrusions and Ore Veins Related to Alkali‐rich Porphyry Deposits in Western Yunnan, China
Authors: Xianfan LIU , Zhengxi YANG , Jiaduo LIU , Dechao WU , Chenjiang ZHANG , Youguo LI
Published: September 2010

Abstract  Western Yunnan is the well‐known polymetallic province in China. It is characterized by copper‐gold mineralization related to Cenozoic alkali‐rich porphyry. This paper analyzes the silicon isotope data obtained from four typical alkali‐rich porphyry deposits based on the dynamic fractionation principle of silicon isotope. The study shows that the ore materials should originate mainly from alkali‐rich magmas, together with silicon‐rich mineralizing fluids. The process of mineralization was completed by auto‐metasomatism, i.e. silicon‐rich mineralizing fluids (including alkali‐rich porphyry and wall‐rock strata) replaced and altered the country rocks and contaminated with crustal rocks during the crystallization of alkali‐rich magmas. Such a process is essentially the continuance of the metasomatism of mantle fluids in crust's mineralization. This provides important evidence of silicon isotopic geochemistry for better understanding the mineralization of the Cenozoic alkali‐rich porphyry polymetallic deposits
Study of the Emplacement Mechanism of the Fenghuangshan Granite Pluton and Related Cu‐Au Mineralization in Tongling, Anhui Province
Authors: Ganguo WU , Da ZHANG , Dongxu LI , Xiangxin ZHANG , Yongjun SHAO , Wenshuan ZANG , Qunfeng WANG
Published: September 2010

Abstract  The Fenghuangshan Pluton is located in the Tongling polymineral‐cluster district in the middle‐lower section of the Yangtze metallogenic belt. In tectonic terms, it is in the middle of the Guichi‐Fanchang faulted fold bundle of the lower Yangtze Platform fold belt between the Dabie Orogenic Belt and the Jiangnan Massif. Analyses of the structural deformation characteristics of both the contact zone and the interior of the pluton are used to explain its emplacement mechanism. The foliation and lineation of the pluton, consisting of the oriented distribution of dark minerals and xenoliths, mainly concentrate along the margin of the pluton. Toward the center of the pluton, the foliation structure becomes weak, showing intense compression formation at the margin, and reflecting the conformable intrusion of the pluton. The relatively gentle lineation is evidence of a rotatory emplacement mechanism. Relatively steep marginal foliation reflects compression expanding. Affected by the thermal power of the pluton, the metamorphism of the contact zone has zonation. Both the strike of the axial plane of fold at the contact zone and that of the flow cleavage of the ductile shear zone are consistent with the boundary of the pluton, which reflects the speciality of conformable intrusion. The hinges of the folds are mostly inclined and erect, reflecting both the rotation of the pluton and its upward spiraling emplacement mechanism. Boudins developed in both the contact zone and the steep strata indicate the emplacement characteristic of the ballon expanding. The surrounding rock of the contact zone shortens horizontally. The average percentage of shortening is 39.7%, which further proves the mechanism of the pluton expanding, and the space occupied by the active expanding intrusion was provided by the shortening of the surrounding rock. The left‐lateral shear shown by the ductile shear zone and the rheomorphic fold reveals that the pluton emplacement and the deformation of surrounding rock are controlled by a NNE‐striking left‐lateral shear stress field. These characteristics of pluton structures provide a mechanism of emplacement. In the deep, the pluton apirally rose left lateral, and in the shallow, the one forcefully emplaced balloningly.
Magmatic Gold Mineralization in the Western Qinling Orogenic Belt: Geology and Metallogenesis of the Baguamiao, Liba and Xiaogouli Gold Deposits
Authors: Jianzhong FENG , Dongbo WANG , Xueming WANG , Yishan ZENG , Tiefeng LI
Published: September 2010

Abstract  The superlarge Baguamiao, large Liba and Xiaogouli gold deposits represent three typical gold deposits different from the Carlin type in the western Qinling Orogenic Belt. Based on Ar‐Ar dating of quartz from ores, U‐Pb dating of single zircon from granite, tracing of H and O isotopes and studies on the mineralogy and texture of spots and bleached alteration developed in wall rocks, this paper focuses the relations between gold deposits and granite to clarify the origin of gold deposits and the metallogenesis in the tectonic evolution of the Qinling Orogenic Belt. The comprehensive studies show that the age of the granite (148.1–244 Ma) is identical with that of the gold deposits (131.91–232.56 Ma). It is suggested that the granite has close temporal, spatial and genetic relationship with the gold deposits. The granite provides a heat source, water source and considerable amount of ore‐forming material. Finally, it is concluded that the orogeny by collision, emplacement of the granite and positioning of the gold deposits represent a successive process. Both the granite and gold deposits resulted from the syn‐orogeny and post‐orogeny tectonic evolution.
GIS Platform‐based Multi‐source Information System for Evaluation of Cu, W and Au Resources in the Northern Qilian, China
Authors: Chunxia LI , Shuixing FU , Shoulin ZHANG
Published: September 2010

Abstract  Based on the information of geology, geochemistry, geophysics and remote sensing, the GIS of multi‐source information is used to evaluate Cu, W and Au mineral resources in Northern Qilian, China. As the GIS evaluation system works out in the thinking of geological prospecting, its functions include file management, graph edition, database maintenance, information inquiry and comprehensive spatial analysis as well as prospecting target prognosis. Accordingly, the GIS evaluation system can be used directly and conveniently for inquiry and analysis of visual graphs or images.
Re‐Os Dating of the Pulang Porphyry Copper Deposit in Zhongdian, NW Yunnan, and Its Geological Significance
Authors: Pusheng ZENG , Zengqian HOU , Haiping WANG , Wenjun QU , Yifeng MENG , Zhusen YANG , Wenchang LI
Published: September 2010

Abstract  The Pulang porphyry copper deposit is located in the Zhongdian island are belt, NW Yunnan, in the central part of the Sanjiang area, SW China, belonging to the southern segment of the Yidun island arc belt on the western margin of the Yangtze Platform. In the Yidun island arc, there occur well‐known “Gacun‐style” massive sulfide deposits in the northern segment and plenty of porphyry copper deposits in the southern segment, of which the Pulang porphyry copper deposit is one of the representatives. Like the Yulong porphyry copper deposit, this porphyry copper deposit is also one of the most important porphyry copper deposits in the eastern Qinghai‐Tibet Plateau. But it is different from other porphyry copper deposits in the eastern Qinghai‐Tibet Plateau (e.g. those in the Gangdise porphyry copper belt and Yulong porphyry copper belt) in that it formed in the Indosinian period, while others in the Himalayan period. Because of its particularity among the porphyry copper deposits of China, this porphyry copper deposit is of great significance for the study of the basic geology and the evaluation and prediction of mineral resources in the Zhongdian island arc belt. However, no accurate chronological data are available for determining the timing of mineralization of the porphyry copper deposit. By field observation in the study area and Re‐Os dating of molybdenite and K‐Ar dating of hydrothermal minerals and whole rock from the typical geological bodies, the timing of mineralization of the porphyry copper deposit has systematically been determined for the first time. The K‐Ar age for the hydrothermal mineralization of biotite‐quartz monzonitic porphyry that has undergone patassic silicate (biotite and K‐feldspar) alteration ranges from 235.4±2.4 to 221.5±2.0 Ma and the Re‐Os age for molybdenite in the quartz‐molybdenite stage is ∼213±3.8 Ma. These data are very close to each other, suggesting that the ore‐forming processes of the Pulang porphyry copper deposit was completed in the Indosinian. But the K‐feldspar K‐Ar age of the main orebodies suggests that the hydrothermal activity related to porphyry copper mineralization continued till ∼182.5±1.8 Ma. This indicates that the lifespan of the hydrotthermal system related to porphyry copper mineralization may have lasted at least 40 Ma. This hydrothermal thermal system with such a long lifespan may be one of the necessary conditions for forming large porphyry copper deposits with a high grade. No late Yanshanian and/or Himalayan magmatism (mineralization) were superimposed in the Pulang porphyry copper deposit.
Lithologic Hydrocarbon Deposits in Rift Lake Basins in Eastern China
Authors: Herong ZHENG , Zongquan HE
Published: September 2010

Abstract  The rift lake basins in the eastern China have abundant hydrocarbon resources of lithologic deposits, which resulted from excellent source rocks and multi‐type sandbodies developed during strong rifting. Vertically, the lithologic deposits are mainly distributed in the lowstand, lacustrine invasion and early highstand systems of third‐order sequence corresponding to a secondary tectonic episode of strong rifting, and laterally they are closely related to various fans and turbidite sandbodies controlled by syn‐sedimentary faults. A variety of lithologic traps have been developed in the rift lake basins, and they generally have favorable conditions of source‐reservoir‐seal assemblage and hydrocarbon accumulation dynamics, indicating that there is a great exploration potential of lithologic deposits in the rift lake basins. In order to obtain satisfactory effects of lithologic deposit exploration, it is required to combine new theories with advanced technical methods.
Tectonic Evolution and Petroleum Systems in the Junggar Basin
Authors: Weifeng WANG , Yequan CHEN
Published: September 2010

Abstract  The Junggar basin is located in the northern part of Xinjiang of China. It is part of the Kazakstan plate, surrounded by the Paleozoic folded mountains: the Halaart, Zayier and Chepaizi Mountains in the northwest, the Qingelidi and Karamaili Mountains in the northeast, and the Tianshan Mountains in the south. In different evolution stages, the basin's types are different, and the stratigraphy and deposition are also different. From the Carboniferous to Tertiary the basin has in turn gone through rift basin, collision foreland basin, intraplate depression basin and regenerated foreland basin. Based on an analysis of thermal evolution history and buried history of the source rocks, three major periods of oil generation are found in the basin. According to the characteristics of source rock distribution, evolution, oil‐source correlation, structure and multi‐phase and mixed pools, the Junggar basin could be divided into 4 composite petroleum systems. Due to the variation in sedimentary facies, difference in structural patterns and development histories, the petroleum pool‐forming conditions in different areas and horizons are greatly different, so are the petroleum pool types, the accumulation mechanisms in different areas and horizons.
Predicting Terrestrial Flagstone Reservoirs in the Sha‐I Member of the Qibei Depression in the Dagang Oilfield
Authors: Huaiyan LEI , Zhihong LIU , Maoquan XU , Baocong GUAN
Published: September 2010

Abstract  There are few 3‐D seismic profiles and drillings in the middle part of the Qibei depression in the Dagang oilfield, and more than 70% of the 2‐D seismic profiles were completed before the 1980s. Meanwhile, changes in the terrestrial formations in this region have been large and complex. These factors have made it difficult to predict reservoirs in this area. The purpose of this paper is to establish a methodology for predicting potential gas and oil reservoirs. Our research combines sequence stratigraphy, well‐logs, and seismic analysis to elucidate the prediction of flagstone reservoirs in the S1 (Sha‐I) Member in the middle of the Qibei depression. Previous research indicates that these rocks were deposited in an environment that had a semiarid, northern subtropical, and warm, humid climate. The objective strata currently consist mainly of lake facies, deeper lake facies, and shore‐shallow lake facies. The study reveals that the lower section of the S1 Member is an important objective region for exploration.
Internal Structure of the Incised Valley Fill in the Hangzhou Bay, Eastern China and Its Geological Implications
Authors: Chunming LIN , Guangyue LI , Baichang WANG , Lianxing GU , Hongchun ZHUO
Published: September 2010

Abstract  This paper presents the sedimentary facies and formation of the Qiantangjiang and Taihu incised valleys, and the characteristics of shallow gas reservoir distribution, based on a large number of data of drilling, static sounding and chemical analysis obtained from the present Hangzhou Bay coastal plain. The incised valleys were formed during the last glacial maximum and were subsequently filled with fluvial facies during the post‐glacial period. All commercial gases are stored in the flood plain sand lenses of the incised valleys.
Leaching Behavior of Fly Ashes from Power Plants
Authors: Guijian LIU , Lianfen GAO , Liugen ZHENG , Haoyuan ZHANG , Zicheng PENG
Published: September 2010

Abstract  The Yanzhou mine district, located in southwestern Shandong Province, is about 1300 km2 with more than 8times109 tons of proved coal reserves and there are 10 big power plants in this area. A large amount of coal ashes, which are regarded as waste materials, have been stockpiled in the area and have influenced the environment of the mine district. In this paper, analysis of fly ash samples from three power plants is carried out, the enrichment and concentration of trace elements, Pb, Zn, Cu and As, in coal ashes are analyzed, and petrological and mineralogical characteristics and chemical compositions of coal ashes are studied. The aim of this work is to provide basic scientific data for utilization of ashes and reduction of environmental pollutions.
Types of Karst‐fractured and Porous Reservoirs in China's Carbonates and the Nature of the Tahe Oilfield in the Tarim Basin
Authors: Kang ZHANG , Darui WANG
Published: September 2010

Abstract  Almost all the oil and gas reservoirs developed in marine sedimentary strata of China have undergone processes of multi‐phase reservoir formation and later modification. The irregular reservoirs are classified into three types as the Naxi, Tahe and Renqiu ones, increasing successively in the development degree of karstificated pores and fissures and the connection degree of independent reservoirs. In these reservoirs, the unity in the fluid feature, pressure and oil‐gas‐water interface also increases successively from the Naxi to the Renqiu type. The main body of Ordovician reservoirs of the Tahe Oilfield in the Tarim Basin is a network pool rather than a stratified, massive, stratigraphically‐unconformed or weathering‐crust one. The fluid nature of oil, gas and water, the interface positions and the pressures, as well as the dynamic conditions of fluids within the reservoirs during the production are all different from those in stratified or massive oil and gas reservoirs. Carbonates in the Akekule uplift and the Tahe Oilfield are assemblages of various types of reservoirs, which have an overall oil‐bearing potential and obvious uneven distribution. Testing and producing tests are the major means to evaluate this type of reservoirs and acid fracturing improvement is a key link in petroleum exploration and development.
Geochemistry of the Cenozoic Potassic Volcanic Rocks in the West Kunlun Mountains and Constraints on Their Sources
Authors: Zhaochong ZHANG , Xuchang XIAO , Jun WANG , Yong WANG , Zhaohua LUO
Published: September 2010

Abstract  The geochemical characteristics of the Cenozoic volcanic rocks from the north Pulu, east Pulu and Dahongliutan regions in the west Kunlun Mountains are somewhat similar as a whole. However, the volcanic rocks from the Dahongliutan region in the south belt are geochemically distinguished from those in the Pulu region; Nd, 207Pb/204Pb and 208Pb/204Pb. Their trace elements and isotopic data suggest that they were derived from lithospheric mantle, consisting of biotite‐ and hornblende‐bearing garnet lherzolite, which had undertaken metasomatism and enrichment. On the primitive mantle‐normalized patterns, they display remarkably negative Nb and Ta anomalies, indicating the presence of early‐stage subducted oceanic crust. The metasomatism and enrichment resulted from the fluid released from the crustal materials enclosed in the source region in response to the uplift of asthenospheric mantle. Based on the previous experiments it can be inferred that the thickness of the lithosphere ranges from 75 to 100 km prior to the generation of the magmas. However, the south belt differs from the north one by its thicker lithosphere and lower degree of partial melting. The different thickness of the lithosphere gives rise to corresponding variation of the degree of crustal contamination. The volcanic rocks in the south belt are much more influenced by crustal contamination. In view of the tectonic setting, the generation of potassic magmas is linked with the uplift of asthenosphere resulted from large‐scale thinning of the lithosphere after the collision of Indian and Eurasian plates, whereas the thinning of the lithosphere may result from delamination. The potassic magmas mainly resulted from partial melting of lithosphere mantle caused by the uplift of asthenosphere.
Thermal Evolution of the Tanlu Fault Zone on the Eastern Margin of the Dabie Mountains and Its Tectonic Implications
Authors: Guang ZHU , Minjin HOU , Yongsheng WANG , Guosheng LIU , Manlan NIU
Published: September 2010

Abstract  Five samples of muscovite from mylonites of the earlier Tanlu ductile shear zone on the eastern margin of the Dabie Mountains yield 40Ar/39Ar ages ranging from 178 Ma to 196 Ma. Three of them have reliable plateau ages of 188.7±0.7 Ma, 189.7±0.6 Ma and 192.5±0.7 Ma respectively, which indicates a syn‐orogenic, sinistral strike‐slip thermal event. This displacement movement derived from the continent‐continent collision of the North and South China blocks took place in the Early Jurassic and after uplifting of high‐pressure to ultrahigh‐pressure slabs to the mid‐crust. It is suggested that during the collision the Tanlu fault zone was an intracontinental transform fault caused by differential subduction speeds. The 40Ar/39Ar ages of mylonite whole‐rock and muscovite from the later Tanlu ductile shear zone suggest another sinistral strike‐slip cooling event at 128 Ma. During this strike‐slip faulting, large‐scale intrusion and doming uplift occurred in the eastern part of the Dabie orogenic belt. Data of K‐feldspar 40Ar/39Ar MDD and apatite fission‐track analysis from metamorphic rocks indicate two high‐speed cooling events experienced by the Tanlu fault zone, which took place at 90 Ma and 45–58 Ma respectively. They correspond respectively to two phases of extensional activities in the Late Cretaceous and Eogene as well as development of the Qianshan fault‐controlled basin to the east of the Tanlu fault zone. The cooling times recorded by K‐feldspar and apatite show that the uplifting in the Dabie orogenic belt occured earlier than that on the eastern margin occupied by the Tanlu fault zone. The above phenomena suggest that the uplifting of the Dabie orogenic belt during the Late Cretaceous to Eogene was not controlled by the Tanlu normal faulting, but as a result of the lithospheric delamination.
Basin Structure and Numerical Simulation for the Mechanisms of Seismic Disasters
Authors: Zhixin ZHAO , Jiren XU
Published: September 2010

Abstract  In the present study seismic wave propagation in heterogeneous media is numerically simulated by using the pseudospectral method with the staggered grid RFFT differentiation in order to clarify the cause for the complicated distribution characteristics of strong ground motion in regions with basin structure. The results show that the maximum amplitudes of simulated ground acceleration waveforms are closely related to the basin structure. Interference of seismic waves in the basin strongly affects the distribution of maximum seismic waveforms, which may result in peak disasters during earthquakes. Peak disasters might be away from basin boundaries or earthquake faults. Seismic energy transmitted into the basin from the bedrock can hardly penetrate the bottom of the basin and then travel back into the bedrock region. The seismic energy is absorbed by basin media, and transferred into the kinematical energy of seismic waves with great amplitude in the basin. Seismic waves between basins may result in serious damage to buildings over the basin. This is significant for aseismatic research. Geological surveys in and around urban areas would benefit aseismatic research and mitigation of seismic disasters of a city. Such geological surveys should involve seismic velocity structure in the media above the bedrock besides such subjects as active faults and geological structure.
Biodegraded Oil and Its High Molecular Weight (C35+) n‐alkanes in the Qianmiqiao Region in the Bohai Bay Basin, Northern China
Authors: Tieguan WANG , Dan ZHU , Hong LU , Zhihuan ZHANG , Chiyin YANG
Published: September 2010

Abstract  With a production of 208.2 m3/d, heavy oil was produced by drill stem test (DST) from three shallow reservoirs in Sand Group Nos. I and III of the Neogene Guantao Formation (NgI and NgIII) and the Eogene Dongying Formation (Ed) in an exploratory well Ban‐14‐1 within the Qianmiqiao region, Bohai Bay Basin, northern China. Based on the GC and GC‐MS data of the NgI and NgIII heavy oil samples, all n‐alkanes and most isoprenoid hydrocarbons are lost and the GC baseline appears as an evident “hump”, implying a large quantity of unresolved complex mixture (UCM), which typically revealed a result of heavy biodegradation. However, there still is a complete series of C14‐C73 n‐alkanes in the high‐temperature gas chromatograms (HTGC) of the heavy oil, among which, the abundance of C30‐ n‐alkanes are drastically reduced. The C35‐C55 high molecular weight (HMW) n‐alkanes are at high abundance and show a normal distribution pattern with major peak at C43 and an obvious odd‐carbon‐number predominance with CPI37–55 and OEP45–49 values of 1.17 and 1.16‐1.20, respectively. According to GC‐MS analysis, the heavy oil is characterized by dual source inputs of aquatic microbes and terrestrial higher plants. Various steranes and tricyclic terpanes indicate an algal origin, and hopane‐type triterpanes, C24 tetracyclic terpane and drimane series show the bacterial contribution. With the odd‐carbon‐number preference, HMW n‐alkanes provide significant information not only on higher plant source input and immaturity, but also on the strong resistibility to biodegradation.
Geological Conditions and Petroleum Exploration Potential of the Albertine Graben of Uganda
Authors: Lirong DOU , Jianjun WANG , Dingsheng CHENG , Xuefeng RAN , RUBONDO Ernest N.T. , KASANDE Robert , BYAKAGABA Abdul , MUGISHA Frank
Published: September 2010

Abstract  The Albertine Graben in western Uganda is a Mesozoic‐Cenozoic rift basin with petroleum exploration potential. A fundamental evaluation of petroleum potential of the graben is given based on field research, data processing of gravity and magnetism, analysis of graben structure, geochemistry, reservoir and composition research. The basin has a double‐layered framework and a large thickness of sediments. Gravity highs shown in a residual anomaly map might indicate central uplift zones. There exist at least two sets of mature or low‐maturity source rocks corresponding to a certain source rock in the Cretaceous or Paleogene and Neogene strata. The graben has basement rock with potential reservoirs and Tertiary sandstone reservoirs and thus has petroleum exploration potential.
Determination of the Neoproterozoic Shicaogou Syn‐collisional Granite in the Eastern Qinling Mountains and Its Geological Implications
Authors: Danling CHEN , Liang LIU , Yong SUN , Anda ZHANG , Chengli ZHANG , Xiaoming LIU , Jinhai LUO
Published: September 2010

Abstract The Shicaogou granite has been identified as a magnesian (Fe‐number=0.71–0.76), calcic to calc‐alkalic (MALI=3.84–5.76) and peraluminous (ASI=1.06–1.13) granite of the syn‐collisional S‐type, with high SiO2 (>71%), Al2O3 (>13%) and Na2O+K2O (6.28%–7.33%, equal for NaO2 and K2O). Trace element and REE analyses show that the granite is rich in LILE such as of Rb, Sr, Ba and Th, and poor in HFSE like Yb, Y, Zr and Hf. Its Rb/Sr ratio is greater than 1; the contents of Nb and Ta, and the ratio of Nb/Ta as well as the REE geochemical features (e.g. REE abundance, visible fractionation of LREE and HREE and medium to pronounced negative Eu anomalies) are all similar to those of crust‐origin, continent‐continent syn‐collisional granite. Moreover, the granite exhibits almost the same pattern as that of the typical continent‐continent syn‐collisional granite on the spider diagram and all samples fall within the syn‐collisional granite field.

The cathodoluminescence (CL) investigations have revealed that the zircon from the Shicaogou granite represents a typical magmatic product characterized by its colorless, transparent and euhedral crystals, and distinct zoning of oscillatory bands. Residual cores of irregular zircon can be found in a few enhedral grains. Trace element studies of the zircon grains, with high contents of P, Y, Hf, Th, U and REE and high ratios of Th/U, obviously positive Ce anomalies and HREE enrichment compared to LREE, also result in the same conclusion.

The LA‐ICP‐MS U‐Pb isotopic data from 24 spots of 21 zircon grains demonstrate that 20 spots in the oscillatory zone yield an average weighted 206Pb/238U age of 925±11 Ma, indicating that the Shicaogou granite was formed in the Neoproterozoic. Combined with other Neoproterozoic syn‐collisional granites found in the study area, the present geochronological determination can further reveal that collision‐amalgamation events could have occurred among some continental blocks in the Qinling orogenic belt during the Neoproterozoic. This in turn provides an accurate chronological constraint on the Neoproterozoic break‐up and convergence in the belt.
A TEM Study on Fluid Inclusions in Coesite‐bearing Jadeite Quartzite in Shuanghe in the Dabie Mountains
Authors: Xiuling WU , Dawei MENG , Yujing HAN
Published: September 2010

Abstract Fluid inclusions at a nano to sub‐micron scale in quartz from jadeite quartzite at Shuanghe, Dabie Mountains, have been investigated by using the transmission electron microscopy (TEM). Most fluid inclusions are spherical or negative crystal shaped, forming wide swarm‐like trails. The TEM reveals that the relationship between coesite and the host quartz is syntaxic and provides strong evidence of the occurrence of high‐salty fluids at peak metamorphic conditions. The fluid inclusions are often connected to dislocations, which are undetected at the scale of optical microscopy. Non‐decrepitation leakage of fluid inclusions may occur by pipe diffusion of molecule H2O or CO2 along dislocations from the inclusions into the host quartz, thus leading to original inclusion density and composition changes. It should be taken into full account for the correct petrological interpretation of micro‐thermometric results.
Calculation of the Model of Coesite Inclusions and Analysis of Their Retrometamorphic Paths
Authors: Dawei MENG , Xiaokun DING , Xiuling WU
Published: September 2010

Abstract The process and path of retrometamorphism of coesite have great significance to our understanding of the P‐T tracks of the exhumation of ultrahigh‐pressure metamorphic rocks. Most of the coesites in the eclogite from Shima, Anhui Province, the Dabie Mountains, China, are found degraded to quartz partly or wholly, with ruptures occurring in the shells, outside which include the coesite and quartz. According to the microscopic observation, the sample of coesite inclusion is composed of garnet, quartz and coesite, based on which we have built a three‐shelled composite sphere model to compute the transition of coesite. Based on the crystal growth formulas and pressure conditions of the ruptures in the garnet, we have calculated the radius of the quartz sphere, which depends on temperature, and eventually drawn the different retrometamorphic paths for different retrometamorphism rates.
Anchimetamorphism of the Neoproterozoic and the Lower Paleozoic along the Profile of Yuanguping in Western Hunan Province, China
Authors: Hejing WANG , Tao CHEN , Huan WANG , Zuqing ZHANG
Published: September 2010

Abstract The Neoproterozoic and Lower Paleozoic along the profile of Yuanguping in western Hunan Province, China underwent anchimetamorphism. The illite crystallinity (IC) of the <2 μm fractions ranges from 0.23–0.34° Δ2θ for the Neoproterozoic to 0.23–0.35° Δ2θ for the Lower Paleozoic (calibrated with the Kisch IC set, Kisch, 1991). This indicates that the metamorphic grade of the Neoproterozoic and Lower Paleozoic is the anchizone. The peak metamorphic temperature is estimated to be 290–210°C. This result does not agree with the greenschist or subgreenschist facies of the Banxi Group, nor with the lower‐greenschist facies or sedimentary cover of the Sinian to Lower Paleozoic, as most previous researchers thought. The illite (K‐mica) b0 values range from 0.9074 to 0.8963 (nm) for the Neoproterozoic and the Lower Paleozoic. Based on cumulative frequency curves of the illite (K‐mica) b0, the peak metamorphic pressure of the Banxi Group was derived to be of a type that is slightly higher than that of the N. New Hampshire low‐intermediate pressure type. Most illites occur as the 2M1 polytype and some in the Neoproterozoic as a mixture of the 2M1+1M types. The distributions of coherent scanning domains (CSDs) of illites along the profile, measured with the XRD method, display a lognormal model and spread out with decreasing Kübler Index of IC. It indicates that illites underwent an Ostwald ripening. The post‐anchimetamorphic structural movement not only results in a series of faults but also induces the lattice strain in minerals along the faults and hence impacts the illite crystallinity and causes diagenetic samples to occur within the anchizone. Compared with the cases in eastern and central Hunan Province, the Neoproterozoic and Lower Paleozoic rocks in the west underwent a lower‐temperature anchimetamorphism with a pressure lower than that in the east and higher than that in the center of Hunan Province.
Compositional Distribution and Growth Mode of Garnet Porphyroblasts during Deformation and Metamorphism
Authors: Guiping ZHAO , Shuwen LIU , Xiaohan LIU
Published: September 2010

Abstract Although porphyroblast microstructures play an important role in structural and metamorphic studies, there are still controversies in the interpretation. The focus is how porphyroblasts grow during deformation and metamorphism. In this paper, we introduce a new approach, the Synchrotron Radiation X‐Ray Fluorescence, to a hemi‐quantitative interpretation of the growth mode of porphyroblasts. The analysis was done at the Beijing Synchrotron Radiation Facility. The specimens were sampled from metapelite of the Baoyintu Group, northern Urad Middle Banner, Inner Mongolia. The new method is successful for determining the microscopic distribution of trace elements in porphybroblasts. The results support the theory of deformation partition, which has been brought forth by Bell and his colleagues, and demonstrate the existence of porphyroblast growth phases and the growth mode of porphyroblasts by hemi‐quantitative mineral chemical analysis. The porphyroblast grows stage by stage in the manner of the distribution of a roseleaf and is controlled by deformation. We call the growth stage of porphyroblast a growth phase.
Large‐scale Migration of Fluids toward Foreland Basins during Collisional Orogeny: Evidence from Triassic Anhydrock Sequences and Regional Alteration in the Middle‐Lower Yangtze Area
Authors: Zengqian HOU , Zhusen YANG , Yinqing LI , Pusheng ZENG , Yifeng MENG
Published: September 2010

Abstract The middle‐lower Yangtze area underwent a series of complex tectonic evolution, such as Hercynian extensional rifting, Indosinian foreland basining, and Yanshanian transpression‐transtension, resulting in a large distinctive Cu‐Fe‐Au metallogenic belt. In the tectonic evolution, large‐scale migration and convergence of fluids toward foreland basins induced during the collisional orogeny of the Yangtze and North China continental blocks were of vital importance for the formation of the metallogenic belt. Through geological surveys of the middle‐lower Yangtze area, three lines of evidence of large‐scale fluid migration are proposed: (1) The extensive dolomitic and silicic alteration penetrating Cambrian‐Triassic strata generally occurs in a region sandwiched between the metallogenic belt along the Yangtze River and the Dabie orogenic belt, and in the alteration domain alternately strong and weak alteration zones extend in a NW direction and are controlled by the fault system of the Dabie orogenic belt; it might record the locus of the activities of long‐distance migrating fluids. (2) The textures and structures of very thick Middle‐Lower Triassic anhydrock sequences in restricted basins along the river reveal the important contribution of the convergence of regional hot brine in restricted basins and the chemical deposition or their formation. (3) Early‐Middle Triassic syndepositional iron carbonate sequences and Fe‐Cu‐Pb‐Zn massive sulfide deposits alternate with anhydrock sequences or are separated from the latter, but all of them occur in the same stratigraphic horizon and are intimately associated with each other, being the product of syndeposition of high‐salinity hot brine. According to the geological surveys, combined with previous data, the authors propose a conceptual model of fluid migration‐convergence and mineralization during the Dabie collisional orogeny.
Quaternary Geology and Faulting in the Damxung‐Yangbajain Basin
Authors: Zhonghai WU , Xitao ZHAO , Zhenhan WU , Wan JIANG , Daogong HU , Chunjing ZHOU
Published: September 2010

Abstract The detailed geological mapping, conducted in the Damxung‐Yangbajain basin, shows that there are many types of deposits formed since the Pliocene. The oldest sediments are formed during the Pliocene. The most prominent sediments are three sets of moraines and fluvioglacial deposits. The ESR, U‐series and OSL dates indicate they are formed about 700–500 ka B.P., 250–125 ka B.P. and 75–12 ka B.P. respectively and indicate that there are three glacial periods since the mid‐Pleistocene in the Nyainqentanglha Range. Along the southeast side of the Nyainqentanglha Range, the main southeast dipping fault zone which bounds the Damxung‐Yangbajain Graben on its western edge was mapped. The fault zone consists of three secondary fault zones and their initiation ages that the fault zones became active gradually decrease southeastward. Prominent faulting occurred in about 700–500 ka B.P., 350–220 ka B.P., ˜140 ka B.P. and 70–50 ka B.P. since the mid‐Pleistocene. The height of fault scarps which offset the sediments formed since the mid‐Pleistocene suggest that the vertical slip rates change between 0.4–2 mm/a and the cumulative average vertical movement at rates of 1.1±0.3 mm/a during the Quaternary period and the Holocene vertical throw rate is 1.4±0.6 mm/a along the fault zones on the western side of the Damxung‐Yangbajain Graben.