Abstract:Abstract：The Yangtze paraplatform is a large craton characterized by development of carbonate formations. Typical Sinian to Middle Triassic cover sediments contain many carbonate formations. Many stratabound Pb-Zn deposits have been found in the carbonate formations on the perimeter of the Yangtze craton and on the margin of its uplifts since the founding of the People＇s Republic of China. In recent years, with the large-scale geological survey,an additional group of very promising Pb-Zn mineralization concentration areas have been discovered in the region. This paper sums up the geological features of these Pb-Zn deposits, compares them with MVT deposits abroad and discusses their ore material source, ore fluids, genetic mechanism and ore controlling factors.

Abstract:Abstract：For the first time trace fossils have been discovered in the Lower Ordovician Sandaokan Formation in the Zhuozishan area at the northwestern margin of the Ordos basin. Most of them are bioturbation structures whose ichnogenera and ichnospecies cannot be identified. The Sandaokan Formation comprises mixed deposits composed of alternating beds of carbonate rocks and terrigenous clastic rocks. It is divided into five members according to the lithology and rhythmicity. The distributions and characteristics of the bioturbation structures and the sedimentary environments where they were formed are analyzed and summarized in this paper. The paleoenvironments during deposition of the formation are mainly foreshore sand beaches, sandbars, dolomite flats, sandy dolomite flats, low-energy subtidal restricted platforms, coquina banks and subtidal open platforms. The characteristics of each paleogeographic unit and paleoenvironments in the depositional period of each member are expounded by the sedimentological and body fossil study, combined with the semi-quantitative analysis of bioturbation structures. It is suggested that the paleoenvironment in the early depositional period of the Sandaokan Formation was successively mainly marked by sandy dolomite flats and low-energy subtidal restricted platforms, while the subtidal open platform environment appeared repeatedly and predominated sometimes in the middle and late depositional periods of the formation, which reflects the general trend of sea-level rise. Meanwhile in the background of transgression, foreshore sand beaches, sandbars and dolomite flats, sandy dolomite flats or subtidal open platforms appeared alternately, which reflects that the Zhuozishan area was near an old land during the Middle Arenigian age. With the periodical rise of the old land or the sea level, transgression and regression and land and sea change occurred frequently; as a result, mixed deposits were developed. Study of the attitudes of the fossil orthocone nautiloids indicate that the paleo-currents were from north to south during the deposition of the Sandaokan Formation. According to analyses of the lithology and fossils, the climate was dry and hot during the deposition of the formation. The Zhuozishan area should be classed as an Early Ordovician North China subtropical dry climatic province.

Abstract:Abstract：Mesozoic volcanic rocks are widely distributed in western Liaoning. The Yixian Formation may be subdivided into four members. The Early Cretaceous Yixian volcanic cycle comprises four subcycles. The first subcycle includes 4 small cycles. From early to late, the magma of the Yixian volcanic cycle evolved gradually from basic through intermediate-basic and intermediate to acidic. The rock association of the Yixian Formation is composed of basanite, trachybasalt, olivine basaltic trachyandesite, trachyandesite, trachydacite and rhyolite. From Beipiao to Yixian volcanic activitiers younged. The diagram of main oxides shows that SiO2 content is positively correlated with K2O and negatively correlated with MgO, CaO and FeO+Fe2O3 .the TAS diagram reflects the volcanic rocks generally have a higher alkalinity. The SiO2-K2O+Na2O and AFM diagrams show that volcanic rocks are of the calc-alkaline series in the subalkaline series. On the SiO2-K2O diagram, most samples fall in the field of the high-K calc-alkaline series and some sample plot in the field of the shoshonite series. Therefore the volcanic rocks of the Yixian volcanic cycle predominantly belong to the high-K calc-alkaline series and partly to the shoshonite series, indicating that they have the basic characteristics of continental intraplate volcanic rocks.

Abstract:Abstract：Calidonian granites are widely developed in the Yema Nanshan area in the western segment of the Qilian orogenic belt. The geochemical characteristics of most of the granites are similar to those of adakites： SiO2≥56%, Al2O3≥15.0%, low MgO (average 2.04%), high Sr (257-889μg/g, average 546.42μg/g), low Y (7.1-25.3μg/g，average 16.67μg/g), average Sr/Y=5.89, no pronounced Eu anomaly and Sr positive anomaly. Adakites in this area have five rock types, quartz diorite, quartz monzodiorite, quartz monzonite, monzogrannite and hornblende granite. These rocks commonly contain hornblende, belonging to I-type granites. The geochemical diagram indicates that the granites formed in a pre-collision island-arc environment, with a zircon U-Pb age of 444±33 Ma, in a plate suduction convergence stage of the Qilian orogenic belt. Therefore, it may be inferred that adakite-like granites of Yema Nanshan formed by partial melting of the subducted slab and crust-mantle magma mixing. This discovery has enriched the study of adakite in China and has great significance for the study of the evolution, geodynamics and metallogenesis of the Qilian orogen.

Abstract:Abstruct：The conjunctional and transitional relation between the West Qinling and East Kunlun orogenic belts, both of which belong to the Central Orogenic System, has long been a focus of dispute in the study of the Central Orogenic System of China. Based on many previous studies of the Buqin Mountain, A′nyêmaqên and Kuhai-Sêrtang ophiolitic mêlange zones in the junction between the two orogenic belts and through further survey and isotope chronological study, the authors find that the three ophiolitic mélange zones are not independent but form a typical triple junction with respect to the composition, textures and structures, geometry and isotope chronology, i.e. the Qinling-Kunlun triple junction. This tectonic system generally experienced a temporal-spatial transition process from the Devonian graben-graben-graben (GGG) type through the Carboniferous-Permian ridge-ridge-aulacogen (RRA) type to the Late Permian subduction-subduction-subduction (SSS) type of triple junction. In the Late Triassic, the process ended, and thus the junction between the West Qinling and East Kunlun was finally completed.

Abstract:Abstract：Cathodoluninescence (CL) images show that there are two types of zircon in the Quli quartz diorite porphyry, Sanmenxia City, Henan Province, i.e. euhedral zircond with fine oscillatory zoning and rounded zircons with an inherited core and growth rims. SHRIMP U-Pb dating of the zircons with fine oscillatory zoning of magmatic origin indicates that quartz diorite porphyry was formed at 117.7±1.6 Ma (Early Cretaceous). SHRIMP U-Pb concordia ages of the cores of rounded zircons are 620 and 219 Ma, suggesting that the parental magma for the quartz diorite porphyry may have been derived from partial melting of basement materials of the South China block that had been modified by ultrahigh-pressure metamorphism.

Abstract:Abstract：The Qiangtang area is a key area to studying the Palaeo-Tethys，and the emplacement timing and tectonic setting of mafic dike swarms in southern Qiangtang have great significance in determining the breakup age of Pangaea and tectonic evolution of the Qinghai-Tibet Plateau. Mafic dikes were dated by using the single-grain zircon U-Pb and whole-rock Sm-Nd methods and the zircon U-Pb concordia age of 312±4 Ma and Sm-Nd isochron ages of 299±13 and 314±5 Ma were obtained.On that basis, combined with the regional geological data, the authors think that the mafic dikes are the product of the breakup of the Qiangtang block and that the isotopic ages represent their emplacement age. This constrains the age of breakup of the Qiangtang block and provides important information for the reconstruction of the formation and evolution of the Lungmu Co-Shuanghu Lake Palaeo-Tethys ocean basin.

Abstract:Abstract：Volcanic rocks in the source region of the Yangtze River contain all the information of the formation and evolution of Cenozoic volcanic rocks in northern Tibet, and its chronological research has important significance for the understanding of the temporal-spatial evolution of Cenozoic volcanic activities in northern Tibet. Based on K-Ar isotope chronological research，Cenozoic volcanism in the source region of the Yangtze River is divided into three phases. In the first phase (40.1-35.1 Ma) volcanism was weak, forming fine-grained latite and porphyritic trachyte of limited distribution. In the second phase (26.5-17.6 Ma), volcanic eruption was strongest,forming extensive thick-bedded, black,vesicular latite. In the the third phase (5.5-4.61 Ma), volcanic mounds of spherulitic-porphyritic trachyte were produced by subvolcanism.The three phases of volcanic eruption in the source region of the Yangtze River correspond with the phases of volcanic activities in northern Tibet. From early to late, the Cenozoic volcanic rocks in the source region of the Yangtze River evolved from high-potassium calc-alkaline series to shoshonite series and from latite to trachyte.

Abstract:Abstract： According to the fossils contained in the Guantou Formation, traditionally the age of the Yongkang Group is assigned to Mid-Late Early Cretaceous. However, the isotopic ages of volcanic rocks of the Guantou Formation are in the range of 113-103 Ma. All the paleomagnetic samples in several basins show normal polarity. Especialy, recently dinosaurian fossil eggs of Faveoloolithidae have been found in the Chaochuan Formation in the Yongkang basin, and the fossil eggs of this family also occur in the Lanxi Formation of the Jujiang Group in the Jinju basin and the Liangtoutang Formation of the Tiantai Group in the Tiantai basin. Furthermore, the paleomagnetic polarity and isotope age of the Yongkang Group are essentially consistent with those of the Tiantai and Jujiang groups. These indicate that like the Tiantai and Jujiang groups, the Yongkang Group is late Early Cretaceous to Late Cretaceous in age, and that there do not exist overlying or underlying relationships between them. They are contemporaneous but heteropic deposits.

Abstract:Abstract：The Late Jurassic-Early Cretaceous strata mainly include the Zhaworong Formation, Xueshan Formation, Bailongbinghe Formation and upper member of the Suowa Formation in the Qiangtang basin. Up to now there are different views about their division, correlation and mutual relation. This paper summarizes the definition and age evidence of each formation and points out that these formations are lithostratigraphic units. The available data are not enough to make a further chronological division. By the statistics of the distribution of various formations and analysis of the sedimentary characteristics of various formations, it is found that the Bailongbinghe Formation is of continental shelf facies and distributed in the northeastern part. Thus the authors think that these formations are contemporaneous and heteropic deposits, and that it is not advisable to consider their relationships to be overlying and underlying. According to this, the authors proposes a new scheme of stratigraphic correlation and think that the highest marine horizon in the basin should extend to the Lower Cretaceous and that seawater retreated from the basin gradually from southeast to northwest.

Abstract:Abstract：The superlarge Carlin gold depost and a metollogenic belt extending over one thousand kilometers were discovered in the western region of the Unitid States in the 1960s. This aroused the attention of various countries in the world. The theory on Carlin type gold prospecting was introduced into China in the 1970s, and after the prospecting practice and preliminary study, the clues leading to finding Carlin type gold deposits were found in Shaanxi and Guizhou, China. A major breakthrough in gold exploration was made in China in the middle and late 1980s, and more than 40 large and intermediate Carlin-and Carlin-like type gold deposits have been delineated in the “nothwest gold triangle” and “southwest gold triangle” at the nothwest and southwest margins of the Yangtze block. Major advances have been made in the study of typical deposits. Mineral exploration reached a higher level in China in the 1990s. In addition to the discovery of a number of deposits, some superlarge gold deposits of this type were successfully found and an integrated study of the ore deposit genesis, metallogenic mechanism, deposit types and metallogenic dynamics was conducted. In the new century, gold deposits have still been found unceasingly. This shows the great potential and good prospects in looking for Carlin- and Carlin-like type gold deposits in northwestern and southwestern regions of China.

Abstract:Abstract：The mineragenic features such as the mineral assemblage of gibbsite, spatial distribution of minerals, mode of occurrence, generations of mineral formation, chemical composition, rare earth elements and water composition inside or outside orebodies in accumulation-type bauxite deposits in western Guangxi have been studied.The results of the study indicate that gibbsite in laterite formed by hydrolytic dissociation of diaspore. The formation of gibbsite occurred under special climatic and geological conditions in the area and was controlled by several factors such as the concentrations of Al3+ and [SiO4] 2- and pH in groundwater. It is supposed to have experienced the stages of precipitation, solidization, devitrification and crystallization of Al(OH)3. In the early stage kaolinite was formed by leaching and secondary quartz was formed at the sites of slight leaching. This kind of bauxite is considered to be not only a new type of deposit but its genesis is also unique. It is degenerating bauxite.

Abstract:Abstract：Based on geological and regional geochemical data and study of the characteristics of regional geochemical anomalies and ore indications of the Wulonggou gold deposit, a regional geochemical anomaly model and ore indications of the Wulonggou gold deposit have been set up. The sieving and evaluation of 1：200,000 regional geochemical anomalies and further improvement of the results of gold geochemical reconnaissance have certain positive significance.

Abstract:Abstract：Permian hydrocarbon source rocks are an important potential hydrocarbon-generating sequence in the Turpan depression, northwestern China. Mainly based on the analytic data of dark mudstone on the outcrop sections, combined with the geochemical data from core samples of hydrocarbon source rocks, the trace geochemistry of mudstone is discussed in detail and the sedimentary environment of the source rocks is analysed by unsing the organic carbon content, organic matter types and saturated hydrocarbon chromatogram parameters of the source rocks. The studies demonstrate that the deposional environment was the weak reducing-reducing one. The terrigenous organisms predominate in the organic matter of the source rocks, and lower aquatic organisms are also present in large quantity. The hydrocarbon is the product of conversion of organic metter deposited in the reducing environment. The depression has a high genetic potential. The sedimentary zones with a strong reducing power and fairly deep water bodies are favorable sites for deposition of primary organic matter, where deposited organic matter can be buried and preserved in time. Therefore most hydrocarbon source rocks contain abundant organic matter and vice versa.

Abstract:Abstract：The paper focuses on the urgent technical issues arising in multi-purpose geochemical survey in plain areas.Based on the data of experimental study, the method for anomaly inspection and ecological appraisal of multi-purpose geochemical survey in plain areas is proposed. In the stage of anomaly inspection, the correlatiom method should be used to determine the geochemical base lines of the anomalous components first, and then classing of anomalies is made to make sure the origin and genetic mechanism of anomalies and provide a theoretical basis for the appraisal of anomaly ecological effect. In the stage of anomaly ecological effect appraisal, it is necessary first to make clear the correlation between the total content of anomalous components and their active components in soil, then to investigate the content correlation between the anomalous components in soil and crops and finally to evaluating the content of heavy metals in crops and their harm to human health through the food chain according to the relevant standards.

Abstract:Abstract:Based on the ore-forming geological backgrounds, the study area is divided into 4 geochemical districts. By using the concentration-area (C-A) multifractal method, the geochemical (anomaly) fields of major ore-forming elements from stream sediments in various geochemical districts have been studied. The results show that owing to different geological backgrounds and different geneses of element concentration, the geochemical (anomaly) fields in these districts have two different multifractal models: the simple multifractal model with only two non-scale sections and the highly clustered multifractal model with more than two non-scale sections, and the element assemblages with the same genesis have similar multifractal features. On that basis, the spatial distribution and concentration pattern of geochemical elements are discussed, and then geochemical backgrounds and anomalies are distinguished. By check and comparison, this method is proved effective and practical.

Abstract:Abstract：The Cretaceous greenhouse climate and paleoceanography is one of hot topics in the Earth sciences during the past twenty years. Observations and ocean models suggest that the climate system and oceanic dynamics during the greenhouse Cretaceous were quite different from their present icehouse patterns. Based on a wealth of geological, geochemical and paleontological data and climatic and oceanographic modeling data obtained in recent years, this paper reviews new advances in the study of the Cretaceous climate and paleoceanography. The fossils and oxygen isotope data reveal that the global mean annual temperature during the Cretaceous was generally 3–10℃ higher than today, and that the mean latitudinal temperature gradient of the ocean is estimated at only　0.15℃/1°– 0.3 ℃/1°. The global oceanic structures and ocean circulation were possibly completely different from those of today, since the forcing of ocean circulation was very likely to be the change in salinity, rather than temperature. Study of Cretaceous abyssal deposits suggests the transformation from the extensive occurrence of carbonate platform facies, black shale interbeds, black shale and oceanic red beds in the Early Cretaceous to predominance of oceanic red beds in the Late Cretaceous. The study of the mechanism of transformation of deposits and its relations to paleo-oceanography and paleoclimate is the main scientific objective of IGCP463/494.