bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics and Genesis of Fine‐Clastic Rock‐Type Au Deposits in the Liaodong Rift
Authors: Dejiang YANG
Published: September 2010

Abstract  Gold deposits occurring in the Liaodong rift are located in interlayered carbonate rocks and fine‐clastic rocks, belonging to the middle and upper parts of the lower Proterozoic. Compared with the Carlin‐type Au deposits abroad and gold deposits in Yunnan‐Guizhou‐Guangxi, Qinling and western Sichuan Province, they are similar in many respects. This paper discusses the geological features of ore‐bearing formations and ore‐filling structures and metallogenetic characteristics. Through the discussion on the sources of ores, heat and water, it points out that the Au deposits belong to vadose reworked hydrothermal deposits. This conforms to the principle of “mineralization in the neighbouring areas”, i.e., the deposits are formed in nearby ore‐bearing layers, and the latest hydrothermal event was the main factor in forming the Au deposits.
Uranium Provinces in China
Authors: Zhaobo CHEN , Fengmin ZHAO , Weidong XIANG , Yuehui CHEN
Published: September 2010

Abstract  Three uranium provinces are recognized in China, the Southeast China uranium province, the Northeast China‐Inner Mongolia uranium province and the Northwest China (Xinjiang) uranium province. The latter two promise good potential for uranium resources and are major exploration target areas in recent years. There are two major types of uranium deposits: the Phanerozoic hydrothermal type (vein type) and the Meso‐Cenozoic sandstone type in different proportions in the three uranium provinces. The most important reason or prerequisite for the formation of these uranium provinces is that Precambrian uranium‐enriched old basement or its broken parts (median massifs) exists or once existed in these regions, and underwent strong tectonomagmatic activation during Phanerozoic time. Uranium was mobilized from the old basement and migrated upwards to the upper structural level together with the acidic magma originating from anatexis and the primary fluids, which were then mixed with meteoric water and resulted in the formation of Phanerozoic hydrothermal uranium deposits under extensional tectonic environments. Erosion of uraniferous rocks and pre‐existing uranium deposits during the Meso‐Cenozoic brought about the removal of uranium into young sedimentary basins. When those basins were uplifted and slightly deformed by later tectonic activity, roll‐type uranium deposits were formed as a result of redox in permeable sandstone strata.
Classification, Minerogenic Models and Prospecting of Realgar/Orpiment Deposits in China
Authors: Xianxiao XIONG
Published: September 2010

Abstract  China's realgar/orpiment deposits may be classified into three types, the stratabound, hot‐water sedimentary and hydrothermal, according to their mineralizing processes, geological occurrences, tectonic and geochemical features. The three types may be further distinguished into seven subtypes, namely, the Xiaguan, Shuiluo, Jiepaiyu, Songpan, Shixia, Wangzhuang and Ninghshan ones. On this basis three minerogenic models are established, and based on studies of their geochemistry and minerogenic mechanisms the prerequisites for prospecting for these types of deposits are given in the paper.
Immature Oils in China and Their Genetic Mechanisms
Authors: Tieguan WANG
Published: September 2010

Abstract  Immature crude oils are a kind of unconventional petroleum resources. They are generated through early low‐temperature biochemical/chemical reactions of some specific organic matter. Their geological reserves explored are as high as several hundred million tons in China. Based on a detailed organic geochemical study, five genetic mechanisms of immature oils have been proposed in this paper for early hydrocarbon generation from suberinite, resinite, bacteria‐reworked terrestrial organic matter, biolipids and sulphur‐rich macromolecules respectively.
Helium Isotope Geochemistry of Ultrahigh‐Pressure Metamorphic Eclogites From the Dabie‐Sulu Terrane in East China
Authors: Yanhe LI , Jincheng LI , Hebin SONG , Xiaochun LIU
Published: September 2010

Abstract: The 3He/4He ratios of most eclogites from the Dabie‐Sulu terrane range from 0.056 to 0.67 Ra; the data points fall into the mixing part of the crust and the mantle in the 3He‐4He diagram. The 3He/4He ratios of eclogites are obviously correlated with the types of their surrounding rocks. The helium isotope composition of the eclogites from the Bixiling complex possesses characters of mantle‐derived rocks with the 3He/4He ratio being 5.6 Ra. The 4He concentration of the eclogites exhibits visible inverse correlation with the δ18O value of the quartz in the eclogites from the Sulu area. The δ18O values of the eclogites change synchronously with those of the country rocks. Those results suggest that protoliths of the eclogites were basic‐ultrabasic rock bodies or veins intruding into the continental crust in the early stage; strong exchange and hybridization between the basic‐ultrabasic rocks and continental rocks and the atmospheric water during the intrusion led to abrupt increase of the 3He/4He ratios, δ18O values and Nd(0) values of the intrusive bodies or veins, which show characters of continental rocks. This indicates that the eclogites are autochthonous.
Types of Enclaves and Their Features and Origins in Intermediate‐Acid Intrusive Rocks from the Tongling District, Anhui Province, China
Authors: Cailai WU , Zhihong WANG , Dewu QIAO , Haibing LI , Meiying HAO , Rendeng SHI
Published: September 2010

Abstract: Enclaves in intermediate‐acid plutons from Tongling can be divided into three types: xenoliths, relics and magmatogenic enclaves. The magmatogenic enclaves consist of cumulates, micrograined dioritite mixtite and dioritic chilled border enclaves. Petrologically, relics with eyed and meta‐poikilitic texture are characterized by high content of biotite (>80%) and low content of cordierite and grossular. The cumulates with accumulate texture consist of a great amount of pyroxene, hornblende and minor spinel and phlogopite. The micrograined dioritic mixtite is composed of more hornblendes and feldspar and less needle apatites and an ellipsoid basic core included in plagioclase. The chilled border enclaves have the same mineral association, but more dark minerals than the host rocks consisting of plagioclase, quartz, alkaline feldspar, hornblende and biotite. Geochemically, the relics exhibit high REE content (455.8×10−6) and high ratio of LREE/HREE, more obvious Eu negative anomaly and are rich in Cr and Ni, poor in Ba, Nb and Sr. All kinds of magmatogenic enclaves have the same REE pattern without Eu anomaly, and the total REE is 74.9×10−6 for spinel pyroxene cumulate, 179.7×10−6 for hornblende cumulate, 226.9 × 10−6 for hornblende cumulate crystal, 289.9×10−6 for micrograined dioritic mixtite and 131.2×10−6 for chilled border enclaves. Calculation with the thermometer and barometer for minerals shows that the temperature and pressure of formation are 1126 °C and 8.44 kbar (7.15–9.04 kbar) for the spinel pyroxene cumulate, 1065 °C‐1029 °C and 8.23 kbar (7.13–9.50 kbar) for the hornblende pyroxene cumulate, 959 °C and 3.40 kbar (2.86–4.09 kbar) for the micrograined dioritic mixtite enclaves, and 951 °C and 0.59 kbar for the dioritic chilled border enclaves, respectively. Thus, the following conclusions can be drawn. Relic enclaves were derived from the crustal partial melting and all cumulate enclaves originated from deep magma chambers near the Moho in the lower crust, which are cumulate fragments formed by fractional crystallization of basic magma; mixtite came from shallow magma chambers in the middle‐upper crust, formed by the mixture of mantle‐derived magma and acid magma derived from the crustal partial melting; and the chilled border enclaves came from the border fragments of early intrusive bodies.
A New Family of Sauropod Dinosaur from the Upper Cretaceous of Tianzhen, Shanxi Province, China
Authors: Qiqing PANG , Zhengwu CHENG
Published: September 2010

A new gigantic sauropod, Huabeisaurus allocotus gen. et sp. nov., about 20 m in length and 5 m in height, was discovered in the Upper Cretaceous Huiquanpu Formation, Tianzhen County, Shanxi Province. It is notably different from Diplodocidae, Titanosauridae and Nemegtosauridae in the following aspects: the teeth are strong, peglike with a length ratio of the tooth crown to tooth root at about 3 to 1; the cervical vertebrae are long with forked spines; the spines in dorsal vertebrae are relatively high, unbifurcated; the caudal vertebrae are amphicoelous, with anterior neural spines and unbifurcated spines and chevrons; the femur is straight and long, narrow and flat and the tibia and fibula are long and flat. These characters show that the described genus should represent a new family, Huabeisauridae fam. nov. The discovery enriches the sauropod dinosaur record in China, and is quite significant to the study of the taxonomy, evolution, migration, extinction and palaeobiogeographic provincialism of the Late Cretaceous sauropod dinosaurs.
A New Sauropod, Gongxianosaurus, from the Lower Jurassic of Sichuan, China
Authors: Yaonan LUO , Changsheng WANG
Published: September 2010

The paper describes an early and primitive sauropod dinosaur, Gongxianosaurus shibeiensis (gen. et sp. nov.), from the Dongyuemiao Member of the Lower Jurassic Ziliujing Formation in Shibei Township, Gongxian County, Sichuan Province, China, which is one of the 5 dinosaur fossils discovered in Gongxian in 1997. Except the skull which is incomplete, the fossils are well preserved. It has some features of both sauropods and prosauropods. It is an intermediate type in the evolution of dinosaurs from prosauropods to sauropods and provides materials for the study of the origin and evolution of the sauropod dinosaur fauna. The discovery of this new sauropod furnishes a way for the stratigraphic correlation between the Early Jurassic Ziliujing Formation in the Sichuan basin and the Lower Jurassic Lufeng Formation in the Central Yunnan basin.
TEM and HRTEM Study of Microstructures in Omphacite from UHP Eclogites at Shima, Dabie Mountains, China
Authors: Xiuling WU , Yujing HAN , Dawei MENG , Weiran YANG , Douxing LI
Published: September 2010

Transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM) analyses have been performed on omphacite from ultra‐high pressure (UHP) eclogites at the locality of Shima, Dabie Mountains, China. TEM reveals that the microstructures consist dominantly of dislocation substructures, including free dislocations, loops, tiltwalls, dislocation tangles and subboundaries. They were produced by high‐temperature ductile deformation, of which the main mechanism was dislocation creep. Antiphase domain (APD) boundaries are common planar defects; an age of 470 ± 6 Ma for UHP eclogite formation has been obtained from the equiaxial size of APDs in ordered omphacites from Shima, coincident with ages given by single‐zircon U‐Pb dating (471 ± 2 Ma). HRTEM reveals C2/c and P2/n space groups in different parts of one single omphacite crystal, and no exsolution is observed in the studied samples, which is attributed to rapid cooling. It is suggested that the UHP eclogites underwent a long period of annealing at high temperatures, followed by relatively rapid cooling. These data provide valuable information for the formation and exhumation mechanism of UHP eclogites in the Dabie high‐pressure (HP) and UHP metamorphic belt.
Outline of Classical and Current Approaches to the Research of Morphology of Selected Mineral Crystals in China (CD‐ROM)
Authors: Wenkui WANG , Shanrong ZHAO , Xinrong LEI , Youcai WU
Published: September 2010

The research on morphology of mineral crystals in China includes classical goniometry of 100 minerals such as hsianghualite, orthobrannerite, jamesonite and bertrandite and surface microtopography of 20 minerals such as wolframite and diamond, among which 5 new minerals and 34 uranium minerals were discovered and measured by Chinese mineralogists. These have enriched mineralogy and crystal morphology and strengthened the study of information of morphological genesis.
Rejuvenation of Fossil Sutures and Related Mesozoic Intracontinental Orogenies in South China
Authors: Genyao WU
Published: September 2010

The Huanan (South China) subcontinent was created by amalgamation of the Yangtze, Xianggan, Cathaysia and Zhemin microcontinents by the Guangxi orogeny in the Early Palaeozoic. The closure of the Tethyan Ocean and subsequent collision event outside the amalgamated continent reactivated fossil sutures and resulted in intracontinental (ensialic) orogenies in the Mesozoic. Based on evidence from deformation, molasse and granitoids, the Sichuan‐Guizhou‐Hunan—southern Hubei and Hunan‐Jiangxi‐Fujian Yanshanian fold‐thrust systems and the Lower Yangtze‐northwestern Fujian Indosinian fold‐thrust system are thought to be intracontinental orogens. Their main features are as follows: intracontinental orogenies occurred areally, thrusting propagated towards the interior of the continental, they extend parallelly to the strikes of the fossil sutures, and the details of the temporal‐spatial evolution of the orogens depend on subduction‐collision events.
An Exploration into the West Henan Large Sliding Structure in the South of the North China Plate
Authors: Chuanxi LIU
Published: September 2010

The West Henan large sliding structure is located in the southern part of the North China plate. It is a planar structural feature of a relatively large scale. To its northwest lie the Taihang Mountains, and to the southwest the Funiu Mountain. In the east it extends between the broad plain and hilly land. Formed in the early Indosinian Period, its main sliding surface is the coal seam II|, with the sliding direction from NW to SE, and a sliding area of about 23,000 km2. Affected by the big sliding, the coal seam II|, in West Henan occurs in the state of powder, and thickens to the SE. Some small penetrating sliding structures were developed over II| in the early Yanshanian Period, causing a disorder on the south border of the North China coal‐accumulating basin in the late Palaeozoic Era. An exploration into the West Henan large sliding structure is of great importance in the geological study.
Tectonic Evolution of an Early Precambrian High‐Pressure Granulite Belt in the North China Craton
Authors: Jianghai LI , KRONER Alfred , Xianglin QIAN , BRIEN P.O.
Published: September 2010

A large‐scale high‐pressure granulite belt (HPGB), more than 700 km long, is recognized within the metamorphic basement of the North China craton. In the regional tectonic framework, the Hengshan‐Chengde HPGB is located in the central collision belt between the western block and eastern block, and represents the deep crustal structural level. The typical high‐pressure granulite (HPG) outcrops are distributed in the Hengshan and Chengde areas. HPGs commonly occur as mafic xenoliths within ductile shear zones, and underwent multipile deformations. To the south, the Hengshan‐Chengde HPGB is juxtaposed with the Wutai greenstone belt by several strike‐slip shear zones. Preliminary isotopic age dating indicates that HPGs from North China were mainly generated at the end of the Neoarchaean, assocaited with tectonic assembly of the western and eastern blocks.
Surface Microtextures of Slipping Zone Soil of Some Landslides in the Three Gorges Reservoir District and Their Significance
Authors: Chunjie YAN , Yunzhi SUN , Huiming TANG
Published: September 2010

The mineral assemblage and content and surface microtextures of slipping zone soil of several landslides in the Three Gorges Reservoir District have been analyzed using the scanning electron microscope (SEM) and X‐ray diffractometer (XRD). All the mineral assemblages are similar in these landslides. The main minerals are montmorillonite, illite, kaolinite, chlorite, quartz and feldspar. There are two kinds of surface microtexture in the slipping zone soil, i.e., linear scratches and arcuate scratches. Based on analyses of the changes of the microtextures, one can obtain information about the number, directions and stages of landslide movements. The authors have also studied the mechanism of landslide formation, evaluated the stability of landslides and revival possibility of ancient landslides and forecasted the activity of similar landslides in different districts. The surface microtexture features of stable landslides and mobile landslides are summarized and it is concluded that the existence of filamentous bacteria may result in or increase movements of landslides.
Research on the Application of the Light‐Energy Spectrum Fusion Technique to Land and Resources Survey
Authors: Yingjun ZHAO , Dechang LIU
Published: September 2010

This paper introduces how to use remote sensing images including Landsat (MSS and TM) and airborne radioactivity images to identify the type of rocks in the areas covered by vegetation. The relationship between light spectrum (Landsat MSS and TM) and energy spectrum (U, Th and K) is discussed on the basis of correlation analysis, and it is proven that there are correlations between the Landsat MSS or TM data and the U, Th and K data. By using the fusion technique, new images were generated, which contain both the light spectrum and the energy spectrum information.

Taking the Lucong basin as the study area, the present paper demonstrates the successful identification of various types of rocks using the fusion technique. Different types of rocks are represented by different colours on the new light‐energy spectrum images, so that volcanic rocks of the Jurassic and Cretaceous periods can be discriminated. Another example, in the Lingquan basin in Northeast China, not only the different types of rocks are successfully distinguished, but corrections and modifications are also made on the original geological map after some field investigation. Practice has proven that the light‐energy spectrum fusion technique is a good way in lithologic identification.
Possibility of the Application of the Ultra‐long Electromagnetic Wave Remote Sensor to Marine Geological Exploration
Authors: Guiting HOU , Xianglin QIAN , Shuyuan WANG , Jing SUN
Published: September 2010

The ultra‐long electromagnetic wave remote sensing technique developed by Peking University is one of new future techniques, which can detect the submarine geological information from the depth of 20 to 10000 m below the surface by receiving natural ultra‐long electromagnetic waves (n Hz to n 100 Hz). The new remote sensor is composed of three parts: a main instrument with a portable computer, an antenna with an amplifier and an external power.

The new remote sensing technique is characterized by good stability and reproducibility at the same spot but at different times and high sensitivity and high signal‐to‐noise ratio, and can reveal geological and lithologic boundaries as well as strata and related mineral sources. Two years of marine geological experiments on this technique have indicated that it can solve many problems in marine geological exploration, e.g. the burial depths of sea‐floor mud, Quaternary sediments and submarine structures. This technique can be applied to detecting the sea bed depth and submarine sediment thickness.
Tests on Application of Soil Magnetic and Integrated Gamma Ray TLD and TC Methods to the Exploration of Sandstone‐Type Uranium Deposits
Authors: Ligui ZOU , Jiyun ZHANG , Jun YAN , Shaobin GUAN
Published: September 2010

This paper introduces the test results of the soil magnetic survey and the integrated gamma‐ray TLD and TC methods for sandstone‐type uranium exploration and describes the prospecting mechanism. The tests have proved that these approaches have yielded good results on classifying the sedimentary facies, defining the redox transitional zones and reflecting deep mineralization information. They may probably become new methods on searching for sandstone‐type uranium deposits.
Petrographic and SHRIMP Studies of Zircons from the Caledonian Xiongdian Eclogite, Northwestern Dabie Mountains
Authors: Ping JIAN , Dunyi LIU , Weiran YANG , WILLIAMS I.S.
Published: September 2010

The Xiongdian eclogite occurring in the Sujiahe tectonic mélange zone at Luoshan County, Henan Province, in the western Dabie Mountains, is typical high‐pressure (HP)‐ultrahigh‐pressure (UHP) and medium‐temperature eclogite. The occurrence, internal texture and surface characteristics of zircons in eclogite were studied rather systematically petrographically combined with the cathodoluminescence (CL) and scanning electron microscope (SEM) methods. Zircons are mainly hosted in garnet and other metamorphic minerals with sharp boundaries, have a multifaceted morphology and are homogeneous or exhibit a metamorphic growth texture in the interior, thus indicating that they are the product of metamorphism. SHRIMP analyses give zircon 206Pb/238U ages of 335 to 424 Ma and show a certain degree of radiogenic Pb loss; therefore it may be inferred that the age of 424±5 Ma represents the minimum age of a HP‐UHP metamorphic age. From the above analyses coupled with previous Sm‐Nd, 40Ar‐39Ar, U‐Pb and 207Pb/206Pb age data, it is suggested that the peak metamorphic age of the Xiongdian eclogite should be between 424 and 480 Ma. This study further validate the view of the existence of a Caledonian HP‐UHP metamorphic event in the western Dabie Mountains.
Geochemical Characteristics and Tectonic Setting of the Laohushan Basalts, North Qilian Mountains
Authors: Qing QIAN , Qi ZHANG
Published: September 2010

Abstract  The Ordovician Laohushan ophiolite, located in the eastern part of the North Qilian Mountains, is mainly composed of meta‐peridotites, gabbros and basalts alternating with sediments. The sediments are mainly turbidites, including sandstones, siltstones, cherts etc. Major elements show that the basalts are subalkaline tholeiites and may be analogous to ocean‐floor basalts. Except a few N‐MORBs, most of the basalts are E‐MORBs as indicated by incompatible element ratios such as (La/Ce)N, La/Sm, Ce/Zr, Zr/Y and Zr/Nb. Negative Nb anomaly is common but negative Zr, Hf and Ti anomalies are quite rare. Based on the geochemical characteristics, it is suggested that the Laohushan basalts were formed in a back‐arc basin. ENd (t) of the basalts ranges between +3.0 and +8.9 and (87Sr/86Sr), ranges between 0.7030 and 0.7060, indicating a depleted mantle source which was mixed with more or less enriched mantle components. Furthermore, the petrography of the sandstones and geochemistry of the cherts suggest that the sediments were deposited near a continental margin.
Relationship between Mesozoic Magmatism and Subduction in the Da Hinggan‐Yanshan Area
Authors: Ji'an SHAO , Futian LIU , Hui CHEN , Qingjun HAN
Published: September 2010

High‐resolution tomographic images of the belt crossing the Japan Trench‐Changbai Mountains‐Dong Ujimqin Qi are represented in this paper, revealing the shape of a subducted slab in the western Pacific region and characteristics of the lithospheric structures under the Changbai Mountains and the Da Hinggan Mountains. Studies of the spatial distribution, subduction time and the time‐lag between the subduction and magmatism, combined with petrology and isotope geochemistry of the Late Mesozoic volcano‐plutonic rocks from the Da Hinggan Mountains‐Yanshan Mountains have further proved the independence of magmatic activities from the subduction of the Pacific plate. The Mesozoic tectono‐thermal evolutionary history and structural characteristics of the lithosphere in the Da Hinggan Mountains and North China suggest that the formation and evolution of magma have probably a close relationship with the delamination and thinning of the continental lithosphere and the underplating resulting from the consequent upwelling of the asthenosphere. On the other hand, the large‐scale strike‐slip fault system, resulting from sinistral shearing of the Pacific plate relative to the Asian continent in the Mesozoic, is responsible for the formation and emplacement of magma on the continental margin. It was the intense crust‐mantle interaction, together with structural deformation at the shallower levels that led to the large tectono‐magmatic belt in the East Asian continental margin.
Geochemical Characteristics of a Veinlet Kupferschiefer Profile from the Lubin Mine, Southwestern Poland
Authors: Yuzhuang SUN , PÜTTMANN W. , KUCHA H.
Published: September 2010

Previous studies have shown that the ascending, oxidizing brines play a very important role in Kupferschiefer mineralization. Fractures could be the pathway of the brines. In order to clarify the influences of the brines on bulk organic matter, aromatic hydrocarbons and Kupferschiefer mineralization, one veinlet Kupferschiefer profile from the Lubin mine, southwestern Poland was studied with the microscopic, geochemical and Rock‐Eval methods. The microscopic results indicate that organic matter of the veinlet sample consists dominantly of bitumen. Its extract content is higher than in other samples. The dominant aromatic compounds are naphthalene and alkylated naphthalenes (Na‐PAH), which have migrated into the veinlet sample from other sediments. The content of phenanthrene and its methylated derivatives (Ph‐PAH) is much lower than in other samples. The reason may be due to their heavier mass than Na‐PAH. It is more difficult for Ph‐PAH to migrate. The Na‐PAH was probably removed from the shale by distillation and enriched in fractures because of their relatively low boiling point. The content of biphenyl and alkylated biphenyls (Bi‐PAH) indicates the influence degree of oxidizing fluids. Their content in the veinlet sample is higher than in other sample. The high Tmax value of the veinlet sample also reveals a more intense influence of the oxidizing fluids than in other samples. Besides the higher Tmax value, its HI value is higher than in other samples. One can presume that its original hydrocarbon content should be higher than this value because they could be partly depleted by the brines.

Five elements (As, Mo, Co, Ni and Bi) are enriched in the veinlet sample, perhaps due to the higher content of extractable bitumen in the fracture, particularly, the high content of Na‐PAH. The higher concentration of the five selected elements indicates that the Kupferschiefer mineralization of veinlet type occurred after the Kupferschiefer deposition.
Numerical Modelling of Ore‐forming Dynamics of Fractal Dispersive Fluid Systems
Authors: Jun DENG , Yun FANG , Liqiang YANG , Junchen YANG , Zhongshi SUN , Jianping WANG , Shijiang DING , Qingfei WANG
Published: September 2010

Based on an analysis of the fractal structures and mass transport mechanism of typical shear‐fluid‐ore formation system, the fractal dispersion theory of the fluid system was used in the dynamic study of the ore formation system. The model of point‐source diffusive illuviation of the shear‐fluid‐ore formation system was constructed, and the numerical simulation of dynamics of the ore formation system was finished. The result shows that: (1) The metallogenic system have nested fractal structure. Different fractal dimension values in different systems show unbalance and inhomogeneity of ore‐forming processes in the geohistory. It is an important parameter to symbolize the process of remobilization and accumulation of ore‐forming materials. Also it can indicate the dynamics of the metallogenic system quantitatively to some extent. (2) In essence, the fractal dispersive ore‐forming dynamics is a combination of multi‐processes dominated by fluid dynamics and supplemented by molecule dispersion in fluids and fluid‐rock interaction. It changes components and physico‐chemical properties of primary rocks and fluids, favouring deposition and mineralization of ore‐forming materials. (3) Gold ore‐forming processes in different types of shear zones are quite different. (1) In a metallogenic system with inhomogeneous volumetric change and inhomogeneous shear, mineralization occurs in structural barriers in the centre of a shear zone and in geochemical barriers in the shear zone near its boundaries. But there is little possibility of mineralization out of the shear zone. (2) As to a metallogenic system with inhomogeneous volumetric change and simple shear, mineralization may occur only in structural barriers near the centre of the shear zone. (3) In a metallogenic system with homogeneous volumetric change and inhomogeneous shear, mineralization may occur in geochemical barriers both within and out of the shear zone.
Geophysical Surveys over Karst Recharge Features, Illinois, USA
Authors: CARPENTER Philip J. , AHMED Shawkat , Xiling Edited By Zhu
Published: September 2010

Karst aquifers supply a significant fraction of the world's drinking water. These types of aquifers are also highly susceptible to pollution from the surface with recharge usually occurring through fractures and solution openings at the bedrock surface. Thickness of the protective soil cover, macropores and openings within the soil cover, and the nature of the weathered bedrock surface all influence infiltration. Recharge openings at the bedrock surface, however, are often covered by unconsolidated sediments, resulting in the inadvertent placement of landfills, unregulated dump sites, tailing piles, waste lagoons and septic systems over recharge zones. In these settings surface geophysical surveys, calibrated by a few soil cores, could be employed to identify these recharge openings, and qualitatively assess the protection afforded by the soil cover. In a test of this hypothesis, geophysical measurements accurately predicted the thickness of unconsolidated deposits overlying karstic dolomite at a site about 100 km south of Chicago, Illinois. Zones of elevated electrical conductivity and high ground‐penetrating radar (GPR) attenuation within the sediments coincided with subcropping solutionally‐enlarged hydraulically active bedrock fractures. These fractures extend to over 12‐m depth, as shown by 2‐D inverted resistivity sections and soil coring. Anomalous electromagnetic (EM) conductivity and GPR response may be due to higher soil moisture above these enlarged fractures. An epikarstal conduit at 2.5‐m depth was directly identified through a GPR survey. These results suggest that surface geophysical surveys are a viable tool for assessing the susceptibility of shallow karst aquifers to contamination.
Water Resource Development in the Quaternary Ryukyu Limestone Regions of Japan: Application of the GIS to the Site Selection of Underground Dams
Authors: JIANG Kaijun , FURUKAWA Hiroyasu , ONOYAMA Yuji , ESAKI Testuro , Xinzhu Edited By Liu
Published: September 2010

Based on the natural and social conditions as well as hydrogeological characteristics of the Ryukyu limestone, a major aquifer in the Ryukyu Islands, a conception of underground dam, was proposed in the early 1970s in order to develop ground water resources in the Quaternary Ryukyu limestone regions of Japan. The practice of nearly thirty years has shown that the underground dam is an environment‐friendly and effective way for developing ground water in these regions.

To further improve the technology associated with underground dam, the authors introduced related analytic methods. The application of the geographical information system technology to site selection of the underground dam is reported in this paper.
Engineering Geology of Limestone in Malaysia
Authors: Boon‐Kong TAN
Published: September 2010

This paper provides an overview of the engineering geology of limestone. Limestone is of rather wide occurrence in Malaysia. It is interesting in view of the unique landforms and karstic features that are encountered in limestone terrains, e.g. steep, subvertical limestone cliffs rising abruptly and majestically above the ground surface and highly variable and pinnacled subterranean limestone bedrock. The karstic features and associated engineering geological problems of both the limestone hills and the bedrock are discussed in the paper. Rockfalls, sinkholes, cavities, etc. are some of the common engineering geological problems associated with limestone terrains. Some local case studies are provided as illustrations. Finally the rock mechanical properties of limestone is discussed at the end of the paper.
On Continent‐Continent Point‐Collision and Ultrahigh‐Pressure Metamorphism
Authors: Shuwen DONG , Hongling WU , Xiaochun LIU , Huaimin XUE
Published: September 2010

Abstract  Up to now it is known that almost all ultrahigh‐pressure (UHP) metamorphism of non‐impact origin occurred in continent‐continent collisional orogenic belt, as has been evidenced by many outcrops in the eastern hemisphere. UHP metamorphic rocks are represented by coesite‐ and diamond‐bearing eclogites and eclogite facies metamorphic rocks formed at 650–800°C and 2.6–3.5 GPa, and most of the protoliths of UHP rocks are volcanic‐sedimentary sequences of continental crust. From these it may be deduced that deep subduction of continental crust may have occurred. However, UHP rocks are exposed on the surface or occur near the surface now, which implies that they have been exhumed from great depths. The mechanism of deep subduction of continental crust and subsequent exhumation has been a hot topic of the research on continental dynamics, but there are divergent views. The focus of the dispute is how deep continental crust is subducted so that UHP rocks can be formed and what mechanism causes it to be subducted to great depths and again exhumed to the shallow surface. Through an analysis of the continental process and mechanical boundary conditions of the Dabie collisional belt—an UHP metamorphic belt where the largest area of UHP rocks in the world is exposed, this paper discusses the variations of viscous stresses and average pressure in the viscous fluid caused by tectonism with rock physical properties and the contribution of the tectonic stresses to production of UHP. Calculation indicates that the anomalous stress state on the irregular boundary of a continental block may give rise to stress concentration and accumulation at local places (where the compressional stress may be 5–9 times higher than those in their surroundings). The tectonic stresses may account for 20–35% of the total UHP. So we may infer that the HP (high‐pressure)‐UHP rocks in the Dabie Mountains were formed at depths of 60–80 km. Thus the authors propose a new genetic model of UHP rocks—the point‐collision model. This model conforms to the basic principles of the mechanics and also to the geologic records and process in the Dabie orogenic belt. It can explain why UHP rocks do not exist along the entire length of the collisional orogen but occur in some particular positions. The authors also propose that the eastern and western corners of the Himalaya collision zone are typical point‐collision areas and that almost all UHP metamorphism of continental crustal rocks occurred in the two particular positions.
Forceful Emplacement of Granitic Plutons in an Extensional Tectonic Setting: Syn‐kinematic Plutons in the Yagan‐Onch Hayrhan Metamorphic Core Complex
Authors: Tao WANG , Yadong ZHENG , Tianbing LI , Yongjun GAO , Mingbo MA
Published: September 2010

Abstract  It is generally considered that granitic plutons are forcefully emplaced in a compressional setting and permissively emplaced in an extensional setting. This paper, however, shows that syn‐kinematic (extensional) elliptic granitic plutons in the Yagan‐Onch Hayrhan metamorphic core complex (MCC) have relatively strong forceful emplacement, which are indicated by (1) concentric distribution of the rock units, (2) a strain pattern with strong strains on the margins and low strains at the centre of a pluton, and particularly (3) syn‐emplacement shortening of the host rocks within the aureole. The strain analysis for the host rocks shows that the host‐rock ductile shortening, i.e. forceful emplacement, provides about 16–24% of the emplacement space for the present plutons. All these suggest that forceful emplacement occurs not only in a compressional tectonic setting, but also in an extensional setting. This study further demonstrates the significance of the multiple emplacement of granitic plutons and provides new information about the causality between granitic magmatism and the formation of the MCC and its dynamics.
Microtextural Characteristics and Origin of Dolomites in the Tepearasi Formation, SW of Beysehir‐Konya, Turkey
Authors: TEKIN Erdoǧan , SARI Ali
Published: September 2010

Abstract  The Tepearasi Formation of the autochthonous Geyikdagi Group in the Central Tauride Belt, SE of Beysehir, is Dogger in age and consists dominantly of massive limestones and greyish dolomites occurring within the middle to upper sections. The total thickness of the dolomitic levels ranges from 100–300 m and laterally extends 500–700 m. Three types of dolomite were distinguished through petrographic analyses: homogeneous, mottled (saddle‐crystalline) and joint‐filling dolomite, which were interpreted to have formed in two different stages, early diagenetic and late diagenetic. The homogeneous dolomite of the early diagenetic stage is light‐coloured and monotonous‐textured and shows the form of a dolosparite mosaic. The mottled dolomite formed in the late diagenetic stage is light‐ to dark‐coloured and coarsely granular idiomorphic. The other type of late diagenetic dolomite, described as the joint‐filling type, presents a crystal growth pattern from the joint walls towards the centre of the joint space. It is associated with coarse calcite crystals as well as primary dolomite crystal clasts which were formed in the early diagenetic stage. In addition to these characteristics, cataclastic texture indicating the influence of tectonism is also observed. Microtexture‐oriented scanning electron microscopy (SEM) studies indicate that mottled dolomites show zonal structures and contain secondary dissolution vugs. SEM studies also revealed the existence of some remains (calcite, clay etc.) in joint‐filling dolomites. Analyses by energy dispersive spectrometry (EDS) indicate the existence of clay minerals (likely to be illite) in the pores of dolomite. Isotope studies conducted to shed light onto the origin of the dolomites of the Tepearasi Formation yielded the results of δ18O=‐2.48 to −3.87%‰ and δ13C=0.93 to 1.12%‰ for the early diagenetic homogeneous dolomites. Mottled and joint‐filling type dolomites of the late diagenetic stage, on the other hand, gave the results of δ18O = −5.42 to −7.12%‰, and δ13C=‐2.29 and −5.70 respectively. X‐Ray diffractometry (XRD) and energy dispersive analysis X‐Ray (EDAX), atomic absorption spectrometry (AAS) analyses, results of petrographic data, and δ18O and δ13C values suggest that the early diagenetic dolomitization in the Tepearasi Formation occurred under the control of hypersaline (rich in Mg) and fresh water mixing zone. The late diagenetic dolomites partly developed under the control of tectonic thrusting.
Collision Event during 177–135 Ma on the Eastern Margin of the Qinghai‐Tibet Plateau: Evidence from 40Ar/39Ar Dating for Basalts on the Western Margin of the Yangtze Platform
Authors: Zengqian HOU , Wen CHEN , Jiren LU
Published: September 2010

Abstract  Geochronology of continental flood basalts sampled from the Emei large igneous province (LIP) on the western margin of the Yangtze platform was investigated by the laser microprobe 40Ar/39Ar dating technique. These basalts yield a fairly wide range of 40Ar/39Ar ages, varying from 259 to 135 Ma. One basalt sample, at least altered, recorded the oldest 40Ar/39Ar age of about 259 Ma, corresponding to a peak eruption age of the Emei LIP continental flood basalts. Most of the samples yield much younger ages from 135 to 177 Ma, which are consistent with the K‐Ar ages for the same samples (122.8–172.1 Ma). The dating data suggest that these Permian basalts had been widely affected by the regional tectonothermal event at 177–135 Ma. The event was probably caused by the convergence and collision among the Laurasia, Yangtze and Qiangtang‐Qamdo continental blocks on the eastern margin of the Qinghai‐Tibet plateau after the late Triassic. The age of the event reflects the timing of the peak collisional orogeny.
Fluid Activity and Tectonic Evolution in the Northern Qilian High‐pressure Metamorphic Belt
Authors: Bin LIU , Kun SHEN
Published: September 2010

Abstract  The Northern Qilian high‐pressure metamorphic belt has experienced multiple deformation‐metamorphism, which consists of at least four stages.

In 550.8–526 Ma, eclogites were formed. High temperature and pressure caused the escape of a large quantity of gas‐liquid fluids from rocks while silicate melt was generated. In the late stage, small amounts of CO2 and H2O infiltrating along fractures were introduced.

In the formation of glaucophane schist (447‐362 Ma), devolatilization reactions were dominated during the subduction‐uplift stage of the paleoplate.

In the uplift‐exhumation stage (400‐380 Ma) the increase of internal space of fractures in the rocks favoured fluid infiltration and concentration. These fluids participated in hydration reactions in the retro‐metamorphism. The fluids participating in the mineral reactions have the compositions of CaCl2‐NaCl‐H2O.

In subsequent thrusting (<380 Ma), the metamorphic terrain was uplifted to the shallower crust and ductile‐shearing deformation took place, which caused mainly dehydration reactions of minerals. In a near‐surface environment the metamorphic terrain experienced brittle deformation, forming many accompanying fractures. Immiscible CO2 and low‐salinity aqueous fluids occurred in these secondary microfractures and were trapped and sealed.

The thermodynamic conditions of different deformation‐metamorphic stages of the metamorphic terrain were calculated and the corresponding P‐T‐t path was deduced, showing that the metamorphic terrain has experienced a clockwise path indicated by T‐ and P‐rising, and T‐ and P‐falling processes. This reveals that the subduction zone has undergone multiple tectono‐dynamic processes, i.e. initial deep burial, subsequent quick uplift and near‐surface tectonism.
The Shengli I Point Bar on the Yellow River Delta: Three‐Dimensional Structures and Their Evolution
Authors: Jianhua ZHONG , Xiaohua SHEN , Jinren NI , Guanmin WANG , Zhifeng WEN , Xibin WANG , Haiqiao WANG , Li LI , Kongyou WU , Yong LI , Mei HONG
Published: September 2010

Abstract  Point bars are well developed on the Yellow River delta, among which the Shengli I point bar is the most typical. The point bar, being about 4 km in length and several tens to more than 100 meters in width, is located on the south side of the Shengli Bridge in Kenli County, Dongying, Shandong. It is a typical fine‐grained point bar with silt, which is predominant, some clay and minor plant debris and clay boulders. The Shengli I point bar has complicated 3‐D structures. Firstly, in a plane view, it comprises mainly eight sedimentary units, bar edge, bar ridge, bar platform, bar plain, bar channel, bar gully, bar pond and bar bay, developing side by side and superimposed one by one in a complex way. Secondly, its vertical structures are very complex due to the partial superimposition of the 8 sedimentary units. Besides hydatogenesis, very intensive wind erosion, eolian, ice and meltwater actions are also visible on the Shengli I point bar. The complex form is made even more complicated because of the above co‐actions.
Temporo‐Spatial Distribution of Rare Metal and REE Deposits in Xinjiang, Northwest China
Authors: Fuwen CHEN , Huaqin LI , Yuanfa LU
Published: September 2010

Abstract  Many rare metal and REE deposits have been found in the Altay orogenic belt, on the northern margin of the Tarim massif and in the Kunlun—Altun orogenic belt, constituting three very important rare metal—REE mineralization belts in western China. These deposits belong to various genetic types with complex ore‐forming mechanism, and were formed in certain mineralization epochs. On the basis of a systematic sum‐up of geologic and geochemical achievements and 40Ar‐39Ar ages of potassium‐rich minerals as well as whole‐rock Rb‐Sr dating results, the authors systematically analyzed the spatial distribution and mineralization epochs of rare metal‐REE deposits in Xinjiang, northwestern China, and concluded that although the Hercynian rare metal‐REE mineralizations in this area are very important, pre‐ and post‐Hercynian (especially Indosinian and early Yanshanian) rare metal‐REE mineralizations also have important theoretical and economic significance.
Quaternary Lake Deposits of Nam Co, Tibet, with a Discussion of the Connection of Nam Co with Ring Co‐Jiuru Co
Authors: Dagang ZHU , Xitao ZHAO , Xiangang MENG , Zhonghai WU , Zhenhan WU , Xiangyang FENG , Zhaogang SHAO , Qisheng LIU , Meiling YANG
Published: September 2010

Shorelines are widespread and lake deposits and lake geomorphology are well developed on the northern Tibetan Plateau. Through field observations of lacustrine deposits of Nam Co—the highest and largest Quaternary lake in Tibet, the authors found four‐step shore terraces composed of sands and clays with well‐developed horizontal bedding and 3–12 m, 15–22 m, 25–30 m and 35–45 m higher than the lake surface respectively, lacustrine deposits resting on the bedrocks and 60–150 m higher than the lake surface, and up to −50 levees composed of oblate lakeshore gravels. Moreover they found lacustrine and lakeshore deposits making up the terraces and levees on the bottoms of wide dividing valleys connecting Nam Co with the Rencoyuema, Rencogongma and Jiuru Co northwest of Nam Co (the valley bottoms are 20 m, 90 m and 60 m higher than the above‐mentioned three lakes) and on slopes north of it, i.e. terraces II and III of Nam Co. Thus they confirm that Nam Co and Ring Co‐Jiuru Co had connected with each other several times, i.e. formed a unified large lake several times, rather than had been different lakes connected only by river channels. From indications such as the distribution of the highest shoreline and lake deposits and geomorphology, the authors conclude that the total area of the old large lakes on the northern Tibetan Plateau is a few times larger than that of the modern lakes and that the last‐stage old large lakes formed in the interglacial interval of the last glaciation.
A Comprehensive Investigation of an Offshore Active Fault in the Western Sagami Bay, Central Japan
Authors: Shiguo WU , SAKAMOTO Izumi , Jiren XU , WONG How Kin
Published: September 2010

Offshore active faults, especially those in the deep sea, are very difficult to study because of the water and sedimentary cover. To characterize the nature and geometry of offshore active faults, a combination of methods must be employed. Generally, seismic profiling is used to map these faults, but often only fault‐related folds rather than fracture planes are imaged. Multi‐beam swath bathymetry provides information on the structure and growth history of a fault because movements of an active fault are reflected in the bottom morphology. Submersible and deep‐tow surveys allow direct observations of deformations on the seafloor (including fracture zones and microstructures). In the deep sea, linearly aligned cold seep communities provide indirect evidence for active faults and the spatial migration of their activities.

The Western Sagami Bay fault (WSBF) in the western Sagami Bay off central Japan is an active fault that has been studied in detail using the above methods. The bottom morphology, fractured breccias directly observed and photographed, seismic profiles, as well as distribution and migration of cold seep communities provide evidence for the nature and geometry of the fault. Focal mechanism solutions of selected earthquakes in the western Sagami Bay during the period from 1900 to 1995 show that the maximum compression trends NW‐SE and the minimum stress axis strikes NE‐SW, a stress pattern indicating a left‐lateral strike‐slip fault.