Abstract:Abstract：According to the lead isotopic composition and geochemical study of rocks, this paper further verifies that the xenoliths of the lower crust carried by an Early Mesozoic andesite-basaltic breccia pipe developed in the Minggang area on the northern boundary of the North Qinling belong to the South Qinling. From below upward the reconstructed section of the lower crust below the South Qinling consists of underplating gabbro, basic granulite (which contains lenses of granulite and gabbro) and acid granulite. The general lithosphere model of the Qinling orogenic belt is as follows: the South Qinling crust (Yangtze block) is detached and subducted northward, the North Qinling crust is obducted toward North China, and the lithosphere beneath North China is injected as a wedge into the Qinling orogenic belt, with the detachment surface lying between the middle and lower crusts. In a plan view, the subducting slab of the South Qinling possibly extends 400 km until it reaches here.

Abstract:Abstract：Simultaneously with the founding of the hypothesis of plate tectonics in the 1960s, another revolution, i.e. quantification of deformation structure analysis instead of qualitative analysis, took place. The important marker of the quantification is the introduction of the Mohr circle construction from mechanics into structural geology and improvement and development of it. The finite strain Mohr circle has been established for the analysis of large deformation and the polar Mohr circle has also been established in order to adapt to general shear deformation. Chinese geologists have made their due contributions.

Abstract:Abstract：The Meso-Cenozoic Yingjisu depression is a piggyback foreland basin developed in the setting of the Paleozoic thrust nappe structure. The sedimentation and deformation of the basin is strictly controlled by thrusts. From north to south the Meso-Cenozoic structure may be divided into seven belts: the northern slope belt, Qongkol-Xinkaiping anticlinal belt, northern Yingjisu synclinal belt, Alagan anticlinal belt, southern Yingjisu synclinal belt, Guchengxu slope belt and Luobuzhuang fault rise. The imbricate thrusts, upthrust structure, structural triangle zones, fault-propagating folds and drape structure are the main deformation styles of the Yingjisu depression. Since the Triassic, the depocenters in different epochs migrated from the orogenic belt to the foreland. The Meso-Cenozoic deformation dynamics and kinematics are related to the amalgamation of plates on the active continental margin of the southern Tarim plate margin and intracrustal detachment-shortening.

Abstract:Abstract：There has been a long dispute about the age of the Bayan Obo iron-niobium-REE deposit. This paper reports the Sm-Nd isochron age and Rb-Sr isochron age of iron-niobium-REE ore samples from the west orebodies of the deposit. The Sm-Nd isochron age is 809±80 (2σ) Ma, with INd=0.511182±34 (2σ) and MSWD=1.10； the Rb-Sr isochron is approximately 391±97 (2σ) Ma, with ISr=0.70453±72 (2σ) and MSWD=47. The Sm-Nd isochron age of the west orebodies is different from the ages of the principal and east orebodies of the deposit obtained with the same chronological method. The Bayan Obo deposit may have formed in the Meso- and Neoproterozoic and undergone subsequent modification of geological processes in the Early Paleozoic Caledonian. As is the case with the principal and east orebodies, the Sr isotope system of iron ore and dolomite of the east orebodies was disturbed or reset in the Caledonian.

Abstract:Abstract：The fundamental principle of Sr isotopic stratigraphy is introduced briefly in the paper. An evolutionary curve of the Sr isotopic composition of the Carboniferous has been constructed based on 19 unaltered carbonate samples collected from the Hiushui section, Guizhou. It was correlated with a contemporaneous Sr isotope curve of North America constructed by R.E. Denison. The very close similarity between the two curves supports the globally consistent evolutionary feature of the Sr isotopic composition of ancient seawater during the geologic history. So the curve is a reliable tool for the global chronostratigraphic correlation. This paper discusses the global sea-level changes during the Carboniferous and the chronostratigraphic division and correlation of the Huishui Carboniferous section. The authors suggest that the Lower-Upper Carboniferous boundary is broadly located near the base of the Bazuo Formation and that the Carboniferous-Permian boundary lies inside the Maping Formation.

Abstract:Abstract：An unusual mantle mineral group consisting of more than 100 species (or subspecies) minerals was discovered in chromite from the Yarlung Zangbo ophiolite belt, Tibet. It includes native element minerals, alloys, oxides (arsenides) and silicates. According to experimental data, some of the minerals are ultrahigh-pressure minerals, possibly formed at the Earth's core-mantle boundary, and are the products of chemical reactions between liquid iron of the Earth's outer core and silicates at the base of the lower mantle； others might be derived from the lower mantle, transitional zone and upper mantle. The mantle mineral group in Tibet has great significance in mineralogy and geodynamics.

Abstract:Abstract：The origin of sillimanite-quartz aggregates in the early Precambrian Wanzhi Group and related rocks in the Pingshan area, Hebei, has long been controversial. According to the geological and geochemical studies they may be divided into three types: (1) globular and nodular sillimanite-quartz aggregates, which form by anatexis of K-feldspar leucogranulitite and are lower in large-ion lithophile (LIL) elements and higher in rare earth elements (REE) and have stronger negative Eu and Ba anomalies than nearby anatectic derivatives; (2) planar sillimanite-quartz aggregates, which form by metamorphic differentiation of K-feldspar leucogranulitite under stresses and show depletion in LIL elements and strong negative Eu and Ba anomalies but no obvious variation in REE and Th contents compared with nearby leucocratic material; and (3) bedded sillimanite-quartz aggregates, which are of metamorphic origin and whose chemical composition are controlled by original rocks.

Abstract:Abstract：On the basis of regional geological mapping, the authors studied Yanshanian rocks in the Dabie area, re-determined the phases of Yanshanian magmatism and found the existence of a complete orogenic magmatic cycle in the area. They for the first time propose that the late Yanshanian magmatic rocks in the area constitute a bimodal association, which combines with the early Yanshanian magmatic rocks (belonging to high-K calc-alkaline-shoshonitic association) to form a compressional to extensional orogenic magmatic cycle. This is important evidence of Yanshanian orogeny. The features of origin of magmatic rocks have revealed that the lithosphere structure in the area experienced a process from double continental crust to normal continental crust in the Yanshanian stage. The deep geological process was the continuation of underplating and delamination.

Abstract:Abstract：Gneissic granites are exposed over large tracts in the Wugongshan (Wugong Mountains) in the eastern “segment on the northern margin of South China. Previous studies suggested that these rocks belong to migmatites” of migmatitic origin. This study has verified that these rocks belong to syntectonic granites. On the basis of a study of the hierarchical units of the rocks, five units have been distinguished, which may be grouped into two super-units. The rocks have U-Pb ages of 462.3±3.2 Ma and 409.4±5.1 Ma respectively, belonging to Caledonian orogenic granites. After their formation they underwent overprinting and reworking of Indosinian-Yanshanian extensional-sliding superimposed structure.

Abstract:Abstract：The West Kunlun area is geographically located at the junction between the northwestern margin of the Qinghai-Tibet Plateau and the southwestern margin of the Tarim basin and tectonically at the junction between the Paleo-Asiatic tectonic domain and the Tethys-Himalaya tectonic domain. It is an important component of the gigantic latitudinal tectonic belt (Kunlun-Qilian-Qinling tectonic belt) across central China. This area has excellent metallogenic conditions in terms of stratigraphy, structure, magmatism etc. The kinds and types of mineral deposit found in the area are highly varied and there is a full range of minerals. In space the minerals show distinct zoning and mineralizations are relatively concentrated. Many kinds of information regarding mineralization indicate that the study area is one of the favorable ore prospect areas for looking for large and superlarge mineral deposits.

Abstract:Abstract：From the Cambrian to Triassic several erosions took place in western Guangxi. It has been largely ascertained that paleokarst surfaces formed during 11 sedimentary hiatuses in the area. Subaqueous karstification that continued for a relatively long period of time during two extensive tectonic uplifts and one rift extension resulted in strong corrosion of mainly Paleozoic carbonate rock series and formation of extensive paleokarst surface. These paleokarst surfaces exerted very pronounced controlling effects on finely disseminated gold deposits. Part of gold deposits do not directly occur on the paleokarst surfaces, but the ore-controlling faults are mostly related to the hidden paleokarst zones at depths. The paleokarst surfaces have played an indirect role in controlling mineralization. The main mineralized rocks include fine clastic rocks, siliceous rocks and basic and intermediate-acid intrusive and extrusive rocks, which are all sialic rocks; whereas the ultimate footwall rocks of the mineralization are all carbonate rocks below the paleokarst surfaces. The mechanism of gold deposit formation is as follows: when tectonism and metamorphism repeatedly occurred on the buried paleokarst hills, gold leached from the strata was concentrated on the paleokarst erosional surfaces or their influence belts and thus the ore formed.

Abstract:Abstract：Through an integrated study of the data of uranium prospecting and exploration of the Shihongtan area in recent years, the paper systematically deals with the conditions of uranium deposit formation, such as the geological structure, depositional environment of ore-bearing rock series, distribution of sand bodies and development features of interlayer oxidation zones and also intensively studies the zoning of the ore-controlling interlayer oxidation zone, shapes, sizes and spatial distribution of orebodies, mode of occurrence of uranium, mineralization age and regularity of uranium mineralization. It further summarizes the regional formation conditions and ore prospects of sandstone-type uranium deposits. With progression of uranium prospecting, the southwestern margin of the Turpan-Hami basin is expected to become a large base of underground leaching sandstone-type uranium resources. This study has great significance for guiding prospecting for underground leaching sandstone-type uranium deposits in the Tianshan orogenic belt and similar areas.

Abstract:Abstract：The geochemical block theory has been applied to analysis and processing of geochemical prospecting data from the whole province of Gansu, and a total of 173 geochemical blocks of 14 elements has been outlined, including 25 geochemical megaprovinces and 148 geochemical provinces. The authors have summarized the spatial distribution characteristics of geochemical blocks and traced the possible localities of occurrence of large to superlarge deposits through a study of the internal structure of the geochemical blocks. By using the metal reserves identified inside the blocks they have calculated the ore potentiality, predicted the metal resources of other elements or other areas, delineated ore prospect areas and determined seven ore targets of giant deposits. Based on a study of the relations between different ranks of geochemical blocks and the metallogenic regions and belts, important geochemical blocks and sub-blocks, metallogenic sub-belts and ore fields have been correlated and the potentials of regional mineral resources inside the geochemical blocks have been evaluated.

Abstract:Abstract：Through 1∶50 000 regional geological survey, the authors have preliminarily ascertained that all the four rock associations in the original Wanbaogou Group are bounded by faults or ductile shear zones and distributed as banded tectonic slices. Mapping has found that the group actually consists merely of volcanic rock associations and carbonate rock associations, in which a Sm-Nd isochron age of 1441±230 Ma and some stromatolites have been obtainsed. So the two rock associations are determined to be of Meso- to Neoproterozoic age. During reconnaissance mapping, the authors found that the original upper and lower clastic rock associations of this group are synonymous, from which predecessors and the authors had found Early Cambrian microfossil plants and small -shelly fossils. On that basis, the original Wanbaogou Group is disintegrated. The disintegrated Wanbaogou Group is only composed of the volcanic rock association and carbonate rock association and renamed the Wanbaogou Group-complex, in which two formal formation-rank tectono-stratigraphic units are established, i.e. the Wenquangou Formation-complex and the Qingbanshisuzhan Formation-complex. On the basis of the fossils and rock associations, the age of the original upper and lower clastic rock associations are revised and identified to be Early Cambrian and a new formation, the Salawula Formation, is established.

Abstract:Abstract：The results of new regional survey has validated the sequence of the Paleoproterozoic Liaohe Group established in eastern Liaoning in the 1970s and the existence of the N-S facies change in the Liaohe Group. The Liaohe Group has all crossed the Yalu River and is distributed over various parts of the Langlin massif. Most of the Langlin Group is equivalent to the Liaohe Group. The main part of the original sedimentary basin of the Liaohe Group occurs as an E-W-trending narrow stripe. It takes the Archean continental crust as the base; in the basin bimodal volcanic rocks are developed. The tectonic attribute is the continental rift. In a few individual central parts, there appears oceanic crust separated from the massif. The paper also discusses the cause for the difference in geology between the northern and southern Archean continental blocks of the ancient basin.

Abstract:Abstract：Qinghai Province is located in the northeastern Qinghai-Tibet Plateau. It is characterized by unique relief and highly varied eco-environments. However, owing to the vast expanse of the province and harsh environmental conditions, the present general features of the eco-environment of the province are little understood. The authors used multi-time-image data and multivariate remote data for image processing methods, and supported by the computer image processing system and through experiments with different image processing methods, they selected the U.S. Landsat-5TM7.4.1 images for extracting remote sensing factors that reflect the integrated features of eco-environment; by referring to the features of the transitional factor and non-remote sensing factors, the authors made eco-environmental division in Qinghai. The whole province is divided into two eco-environmental regions, seven eco-environmental subregions and 31 districts. Through this study, the authors have got a macroscopic understanding of the present state of the eco-environment in Qinghai and also reached the aim of discussing the relevant techniques used in the application.

Abstract:Abstract：According to different hydrogeological and characteristics of karst areas as well as the characteristics of groundwater circulation and by applying the systematic analytic method, the karst water systems may be classified into three grades: the first grade is the karst water system; the second grade includes the shallow-circulating and deep-circulating karst water systems; the third grade may be further divided into six basic karst hydrogeological units or types, exposed, exposed-covered, exposed-buried, perched water, deep-buried stratabound and fault zone types. The paper also discusses the hydrogeological characteristics of the various types and points out the significance of various systems in water supply. This study is of reference value for the exploration and development of karst water resources in down-faulted basins.