Abstract:This paper revised the chronology of major late Cenozoic tectonic events in east Tibetan Plateau, mostly based on records of stratigraphy in the basins and magmatism and deformation along active fault zones, with the purpose of establishing an evolution history of extrusion-related orogenic system. It is shown that the most important event, as previously named the Qingzang movement, was initiated at 12-8 Ma and lasted to early Pliocene, with a duration of 6-8 Ma. The crustal fragments in east Tibet, such as the Chuan-Dian, Chuan-Qing, Longzhong blocks, were orderly extruded eastward accommodated by large-scale sinistral strike-slip faults like the Xianshuihe, East Kunlun and Haiyuan faults. This eastward extrusion was concomitant with thrusting, which resulted in fast uplift of the ranges along its eastern edges, and went beyond this margin through decollement, generating folds of the cover rocks like the Longquanshan, Daliangshan in the Yangze craton. The deposition of late Pliocene conglomeratic layer, namely the Dayi conglomerates along the eastern foreland zone, the Jishi conglomerates and the Wuquan conglomerates at the northeast corner of Tibet, marked the emergence of contrast geomorphology in this region. Late Pliocene to early Pleistocene (3.6-1Ma) corresponds to a period of tectonically quiescence or relaxation, during which a set of N-S trending rift basins, such as Yuanmu, Yanyuan, and Anninghe, were developed along the eastern margin, and accumulated a series of fluviao-lacustrine facies deposits in these basins. This relaxation stage was followed in Early-Middle Pleistocene (1.0-0.6 Ma) by an important compressional event named the Kun-Huang or Yuanmu event, which caused further uplift of east Tibet. Active faulting pattern in east Tibet has been changed greatly since the late Pleistocene (about 120 Ka), featured along its southwest part by clockwise rotation around the east Himalaya syntax of two sinistral strike-slip fault zones, and along its central north part by a counter clockwise rotation accommodated by dextral strike-slip motion in the Longmenshan fault zone and eastward push of the Qinling range. The lower crustal flow could be a major driven mechanism for the deformation of this most recent stage.

Abstract:On the basis of previous studies in conjunction with granite dating and geochemical study results in this paper, the South Altun granite can be divided into five episodes:episode 1, characterized by the granite association of quartz diorite+granodiorite+monzogranite, with affinities of I-type granite and an age of >460 Ma; episode 2, characterized by the granite association of granodiorite+monzogranite+syenogranite, with geochemical affinities of I-type granite and an age of 435-450 Ma; episode 3, characterized by the granite association of monzogranite+syenogranite+alkali feldspar granite, with affinities of A-type granite and an age of 385-411 Ma; episode 4, characterized by the granite association of granodiorite+monzogranite with an age of 343-352 Ma, with geochemical affinities of S-type granite; and episode 5, characterized by the granite association of quartz diorite+monzogranite+syenogranite, with geochemical affinities of I-type granite and an age of 265 Ma. Zircon Lu-Hf isotope analysis of granite in various episodes showed that ε_Hf(t) values are positive in most cases and negative for a small number of inherited zircons, indicating that their source rocks were mainly juvenile crust mixed with a minor amount of ancient continental components. Based on the results of the above studies in conjunction with regional geological characteristics, it is considered that episode-1 granitic magma activity might be related to the subduction of oceanic crust, episode-2 magma activity might belong to post-collisional magma activity, episode-3 magma activity might be related to the isostatic adjustment of orogen blocks after plate collision, and episode-4 and episode-5 magma activity might be related to the delamination of deep blocks under the southern Altun orogen.

Abstract:Archean basement rocks are well preserved in the Lushan area. In this study, zircon SHRIMP U-Pb dating results suggest that two samples, collected from the Weizhuang gneiss in Lushan, record magmatic age of 2867±5 Ma and 2768±5 Ma, respectively. They underwent metamorphism at 2775±6 Ma and 2775±56 Ma, respectively. Together with data available, the protoliths of the Weizhuang Gneiss formed at two stages, i.e., 2867-2928 Ma and 2765-2768 Ma, while protoliths of the Yushuzhuang Gneiss and amphibolite formed at three stages (2829-2897 Ma, 2752-2778 Ma and 2723 Ma versus 2838-2845 Ma, 2747-2794 Ma and 2730 Ma). Although the three types of rocks are different in lithology, they record similar magmatism phases, indicating the existence of genetic connections among them. Recently, 2.8-2.9 Ga rocks were identified in many areas, indicating the existence of Mesoarchean basement on a certain scale in Lushan. Compared with the Precambrian evolution of Jiaodong and Huoqiu, it is concluded that a Mesoarchean block, which underwent a significant crustal growth event at 2.9-3.0 Ga, may be present along the southern margin of the North China Craton.

Abstract:Located in the northeast of the Duolong ore concentration area in the Bangong Co-Nujiang metallogenic belt, Tibet, the Sena copper (gold) deposit has favorable prospecting potentiality. The quartz diorite porphyrite in the deposit whose zircon U-Pb age is (118.1±1.4) Ma is consistent with the age of reported arc-type ore-bearing porphyry in the Duolong ore concentration area. They belong to high-K calc-alkaline to calc-alkaline and metaluminous I-type felsic rocks. These porphyries are systematically enriched in large-ion lithophile elements (LILE such as Th, U, K, Pb and Rb) and LREE, relatively depleted in high strength elements (HFSE such as Ta, Nb, Ti and Zr) and HREE. And they are slightly rightly-oblique, show the fractionation between LREE and HREE, and display no Eu anomalies (δEu=0.92-1.04). According to the regional tectonic setting, the authors hold that the geochemical characteristics of the quartz diorite porphyrite are consistent with those of arc-type magmas in the world, and the closure time of this ocean should be later than early Cretaceous (118Ma). The Rb/Sr ratios (0.143-0.195), Zr/Hf ratios (31.23-34.14), and Nb/Ta ratios (9.21-11.59) suggest that the melts had characteristics of crust mantle mixing. The zircon (¹⁷⁶Hf/¹⁷⁷Hf)_i, ε_Hf(t) and T_DM2 are 0.282707-0.282719, 0.28-11.77 and 424-1159 Ma, respectively, indicating that the rocks probably represent the remelting products of juvenile crust, also impacted by minor mantle-derived mafic melts under the background of northward subduction of Bangong Co-Nujiang Tethys to Qiangtang massif.

Abstract:Triassic intrusive rocks (TIRs) are widespread in Binbalechagan area of Dong Ujimqin Banner in Inner Mongolia, and hence this area has advantage of studying Early Paleozoic evolution of central-east segment of Central Asia Orogenic Belt (CAOB). Based on regional geological survey, the authors recognized two Triassic magmatic activities by evidence from geochronology:mid-Triassic adamellites(with isotope ages of 238-230 Ma)and late-Triassic syenogranites (with isotope ages from 223 to 215 Ma). The former rocks whose geochemical features are between I-type and A-type granites are characterized by magnesia biotite, high silicon, rich K, peraluminum and calc-alkaline nature, abundant light rare earth elements and large ion lithophile elements, and significant negative Eu and Ba anomalies. However, the latter rocks belong to A-type granites and are characterized by high silicon, enriched alkali, abundant K and, weak peraluminum nature. Otherwise, total REE in the latter is lower, and negative anomaly degrees of Eu and Ba in the latter are more obvious than those of the former. These TIRs probably originated from partial melting of the lower crust which consisted of newly derived mantle. In combination with regional information, it can be concluded that the TIRS was formed after the closure of the Paleo-Asian Ocean. In mid-Triassic, the study area probably was in post-orogenic background, and hence this area was mainly in an intraplate tectonic setting in late Triassic.

Abstract:Late Carboniferous quartz diorites are distributed in the Xi Ujimqin Banner of Inner Mongolia. The results of LA-ICPMS zircon U-Pb dating of the quartz diorite samples indicate ages of 304.64±0.82 Ma and 309.84±0.86 Ma. In addition, new geochemical data from six quartz diorite samples are presented. All six samples show high Al₂O₃ values but low TiO₂ values, and are thus classified as calc-alkali basalt series. These samples are characterized by low REE abundance and slight LREE enrichment. They also show LILE enrichment, HFSE depletion and distinctly negative Nb and Ta anomalies. All of these characteristics resemble those of arc magmatic rocks. Furthermore, as shown in the correlation plots of La/Ba versus La/Nb, Ba/La versus Ce/Pb, and Nb/Y versus La/Yb, the magma source has experienced contamination and metasomatism from the subduction fluid. According to the Zr/Nb, La/Nb, La/Ta ratios and the diagram of Sm/Yb versus La/Sm, the magma was derived from the shallow lithospheric mantle and formed by moderate (10%-20%) partial melting of spinel-garnet lherzolites. Based on geochemical characteristics of these samples in this study, combined with regional geological data and previous research results, the authors hold that, in the late EarlyCarboniferous, there was a new limited ocean basin under an intensely extensional rift setting. Consequently, as the newly formed ocean basin was still immature or experienced subduction-related contamination and metasomatism, the Late Carboniferous quartz diorites of Xi Ujimqin Banner exhibited the continental margin-arc-like enriched signatures.

Abstract:The Jiujingzi ophiolite belongs to the eastern segment of the Xar Monron River ophiolite belt in southeastern Inner Mongolia. In this paper, the authors carried out zircon U-Pb dating of a gabbro dike of the Jiujingzi ophiolite and the surrounding siltstone that is in fault contact with the ophiolite. The results indicate that the gabbro dike was formed in late Early Permian (274.7± 1.7 Ma, MSWD=0.079). Considering previous geological data on strata, paleontology and magmatic rocks, the authors hold that there was still an ocean basin in late Early Permian in southeastern Inner Mongolia. The detrital zircons of the adjacent siltstone constitute four age peaks:2350-2700 Ma, 1700-2100 Ma, 370-470 Ma and 250-290 Ma. A comparison with regional tectonothermal events shows that the provenance of the siltstone was mainly from the north margin of the Sino-Korean paleoplate. The age of the youngest zircon is late Early Permian-early Early Triassic (249±4.7 Ma), which is similar to the ages of the disappearance of the marine strata in southeastern Inner Mongolia, the mixing between the Cathaysian and Angaran floras, the convergence of the palaeolatitude curves of the Siberian and Sino-Korean paleoplates and the formation of the collision-related magmatic rocks. It is thus suggested that the tectonic emplacement of the Jiujingzi ophiolite might have occurred in late Early Permian-early Early Triassic, which might represent the final closure time of the Paleo-Asian Ocean.

Abstract:During the cone-forming stage of Tianchi volcano, activity of basaltic volcanism was frequent. In this paper, based on field geological survey and analysis of chronology and geochemistry, the authors determined active stages of the basaltic volcanism,and investigated magmatic source and evolution. The results show that the activity of the basaltic volcanism forming scoria cones or mini valley basalt can be divided into 2 stages:Laofangzixiaoshan period (about 0.87-0.54 Ma) belonging to alkaline basaltic volcanism and Laohudong period (about 0.34-0.1 Ma) belonging to alkaline and tholeiitic volcanism. Alkaline basalt is rich in Al, Ti, K and P, and poor in Mg, and tholeiite is rich in Mg, Fe and Ca, and poor in Na. The two types of basalt have similar characteristics in REEs, trace elements and Eu anomalies, exhibiting obvious right-declined REE patterns, slightly positive Eu anomalies, enrichment of Ba, K, Pb, P and Ti, and depletion in Th, U and Sr. Nevertheless, in contrast to alkaline basalt, content of REEs and trace elements, and fractional degree of HREE and LREE are lower in tholeiite. The basalt formed during the coneforming stage of Tianchi volcano was derived from evolutional magma, and was identical with the transitional position of uppermantle and lower-crust, which had characteristics of common fountain, and had the same or similar evolution process with significant crystallization differentiation and faint crustal contamination. Compositions of the evolutional magma were controlled by multi-stages crystallization differentiation and recirculation during early crystallization.

Abstract:The magmatic event of Yanshanian period in South China has been divided into two stages:Early Yanshanian (180-150Ma) (J₂-J₃) and Late Yanshanian (140-80Ma) (K₁-K₂). However, there exist only the data concerning Cretaceous mineralization associated with acidic intrusive rocks, but the record of the early magmatic events on the southwest margin of the Yangtze Plate has not been seen. In this paper, the authors newly discovered Maidicun lamprophyre in Jianshui area of eastern Yunnan. The U-Pb age of the zircon is 158.4±2.4 Ma (MSWD=4.2), and hence it is obvious that the lamprophyre was formed in the Late Jurassic, corresponding to the first stage of the thermal event in southeast China. The values of incompatible elements are significantly higher than those of the primitive mantle of Maidicun lamprophyre, showing different degrees of enrichment. The LILE (Rb, Ba, Ce) enrichment is not obvious, HFSE (U, Ta, Pb) show some enrichment, and Nb, Ti, Zr, Hf don't show significant enrichment and losses. LREE/HREE ratios are in the range of 5.65-6.07, averagely 5.89,(La/Yb)_N ratios are in the range of 7-12, indicating LREE enrichment and HREF relative losses. It has no negative anomalies of Nb-Ta-Ti and shows REE characteristics of OIB-type oceanic island basalts, and the Maidicun lamprophyre was formed under the condition of intraplate extension. NNE-trending structures were developed in the study area during the Mesozoic, and the early NNE-trending folds were superposed by late normal faults in the same direction. The fold axial surface is mainly SE-trending and partly NW-trending, indicating tectonic characteristics in response to SEE-NWW trending extrusion stress. Faults are mostly high-angle normal faults in the NW-SE direction, showing that they were influenced by EW-trending tensile stress. The lamprophyre's intrusion was mainly controlled by the action of deep asthenosphere mantle, from which the fluid experienced metasomatism with lithosphere mantle in response to partial diapering of asthenosphere and the stretch of lithosphere in eastern Yunnan in the Late Jurassic period, followed by the formation of the enriched mantle. And this kind of enriched mantle was partially heated, melted and migrated upward for emplacement finally. The intrusion age of the lamprophyre (Late Jurassic 158 Ma) is the starting time of extension in the study area.

Abstract:The Sibao Group, outcropped in the north part of Guangxi and southeast part of Guizhou, is composed of over 5000 m thick succession of strongly-deformed, low-grade metamorphic volcanic rocks and terrigenous clastic rock, overlain unconformity by the Danzhou Group (Xiajiang Group). It is divided into three Formations:Jiuxiao Formation, Wentong Formation and Yuxi Formation. Sample A20140731-3 is lava, collected from the upper part of the Wentong Formation, and over 600 grains of zircon were sorted out from it. Fifteen of the zircons were analyzed with SHRIMP, and a weighed-mean U-Pb age of(860±13) Ma was obtained, which indicates that the volcanic rocks of the Sibao Group belong to Neoproterozoic. Based on this new zircon SHRIMP U-Pb age combined with the other high-quality ages obtained recently in the Jiangnan Orogen, the authors investigated the stratigraphic correlation between Sibao Group and the other main strata, such as Lengjiaxi Group, Shuangqiaoshan Group, and Fanjingshan Group.

Abstract:Systematic analysis of petrology and geochemistry of Xishanbulake Formation argillaceous rocks in Tseganbrark was made in this study. The purpose of this paper is to discuss sediment provenance, weathering and tectonic setting of sedimentation basin. The ratios of Al₂O₃/TiO₂, Th/Sc, (Gd/Yb)_N,(Eu/Eu^*)_N, ICV, CIA of argillaceous rocks in Qieganbulakedaban are 24, 0.9, 1.1, 0.6, 1.2, 70 respectively, while these ratios in Moheershan are 10.5, 0.2, 3.5, 1.01, 2.8, 75 respectively. These characteristics indicate that all of argillaceous rocks tended to occur in first-cycle deposit. The source rock of argillaceous rocks in Qieganbulakedaban were granitoids formed in a stable intracontinental environment, whereas the source rock of them in Moheershan were basicintermediate magmatic rocks formed in a volcanic uplift environment. Under the tectonic setting of Rodinia Supercontinent cracking, the cracking of Moheershan was stronger than Qieganbulakedaban. The CIA in the study area demonstrates that the source region of argillaceous rocks suffered from medium degree chemical weathering which reflects a warm and moist climate located in 30°S. The CIA characteristics of vanadium-bearing carbonaceous shales and phosphorite suggest that the sources of vanadium and phosphorus were connected with basic-intermediate magmatism in Sinian and Cambrian.

Abstract:Through field geological investigation and elaborate observation of Olongbluk micro-massif on the north margin of Qaidam Basin in combination with the rock, sedimentary structural characteristics and contact relationship of strata in the profiles,the authors studied features of the Early Paleozoic Cambrian to early Ordovician sedimentary and lithofacies palaeogeography in the study area. Olongbluk micro-massif is located in a volcanic island arc back-arc area, and ocean subduction and collision of continental plates control basin-orogen pattern and evolution of sedimentary fillings in North Qaidam. The lower Paleozoic period of Olongbluk micro-massif mainly developed a set of marine carbonatite, with some terrigenous detrital rock in Cambrian bottom and early Ordovician strata. According to lithological association, there are five kinds of sedimentary facies, i.e., evaporated tidal flat facies, restricted platform facies, open platform facies, platform edge facies and flysch sediment. The study area mainly experienced transgression impact in that epoch. In Early Cambrian period, the study area received evaporation tidal flat sediments. In middle and Late Cambrian period, the study area accepted a set of shallow sea carbonatite formation, and the transgression range was enlarged, thus belonging to an area of restricted platform-open platform sediments. In Early Ordovician period, the sedimentary environment shifted into shoal of platform margin facies-foreslope. In the late of Early Ordovician period, the platform migrated southward, and became platform margin or slope under the compensated deep shelf sedimentary environment.

Abstract:Located in the west beach of Pacific Ocean and the mouth area of Yangtze River, the Yangtze delta area is doubly affected by the sea and the regional big river. Therefore, the sedimentary environment is very complex. The NB5 hole is in the north of Yangtze delta area. The NB5 hole at Xiting Town of Nantong City was drilled 362 m deep with 354m thickness of Quaternary strata. According to testing results of paleomagnetism, ¹⁴C and ESR of NB5 core, analyzing the lithological character, and a comparison with other cores in this area or nearby areas, the strata were divided and the environment evolution since the Quaternary was investigated. The result indicates that the bottom of Holocence is at about 46 m, the top of middle Pleistocene is at about 163 m, the top of lower Pleistocene is at about 240 m, and the bottom of lower Pleistocene is at about 354 m. There are five marine face layers in the core which are located 2-47m and 125-163 m. they are the 1^st transgression layer (Zhenjiang transgression) and the 3^rd transgression layer (Kunshan transgression), because there exist remarkable different lithological characteristics and magnetic susceptibilities above 163 m and below 163 m in the core. The authors hold that the Gonghe movement that occurred in late middle Pleistocene might have affected the environment of this area greatly so that the main river flowed through this area.

Abstract:The Wunite depression is one of the five depressions in the Erlian Basin. A series of grabens/half grabens were developed under the action of regional extension in Early Cretaceous. Extensional fault and transform structure form the extensional structures. The major boundary faults (MBF) are listric faults, slipping deep in the mélange zone and being shallow in complex synclines. The MBF extends like a simple arc or a wave. Accommodating/propagating displacement is realized through transfer fault or strike ramp. Divergent TZ and convergent are the main transfer structures between faulted-sags. And the MBF tendency often changes through the divergent or convergent TZ. In the early Early Cretaceous, lots of independent small-scale faulted-sags filled Wunite Depression; in middle Early Cretaceous, with the continuing of extension, adjacent faults were laterally propagating to become the regional boundary fault and adjacent faulted-sags were connected to become the complex faulted-sag; in late Early Cretaceous, the depression entered into the post-rifting stage.

Abstract:In this paper, the authors utilized cores and thin sections observations, SEM, cathodoluminescence and physical property analysis to study characteristics and diagenesis of the reservoir within Upper Permian Changxing Formation, and preliminarily established diagenetic evolution sequence. The interval is mainly featured by platform margin reef-shoal around KaijiangLiangping trough in eastern Sichuan Basin. Reservoir characteristics reveal that the Changxing reservoirs are developed well. Reservoir rocks are composed of"piebald"bioclastic dolomite and reef dolomite dominate, whereas reservoir spaces mainly comprise intergranular pores, dissolved intergranular pores and dissolved intragranular pores. The reservoir porosity is mainly between 2% and 6%, and the permeability is between 0.1 mD and 1 mD. Four types of reservoirs were found, i.e., "low-porosity and high-permeability" type, "medium-porosity and medium-permeability" type, transitional type and "high-porosity and lowpermeability" type. The diagenetic evolution indicates that Changxing Formation experienced cementation, compaction, dolomitization, dissolution and tectonic fracturing. A decreasing trend in porosity due to the superimposed modification by multiplephase diagenesis was observed. Cementation and compaction occupied most of primary pores and reduced the porosity after the deposition. Karstification and dolomitization improved the porosity by transforming the textures of pores. Tectonic fractures further optimized the reservoir. Research shows that primary intergranular pores and eogenetic secondary pores formed by eogenetic karstification and hydrothermal dolomitization not only serve as the prototype of reservoir space but also generally determine the final appearance of the reservoir.

Abstract:In order to study the pore characteristics of shale gas reservoirs on the eastern margin of Ordos Basin, the authors selected the shale in Ye-1,Ye-4 and DT803 wells for experiments including scanning electron microscope, nitrogen sorption-desorption experiments and related geochemical experiments. Meanwhile, the transitional facies shale pore types, characteristics and influencing factors of gas reservoir were analyzed. The results show that inter-granular pore and organic pores are most developed in the shale, the pore morphology of the shale is mainly in the narrow parallel-plate, the pore size distribution range is 1-60nm, and the main pore size distribution is between 1-6nm and 40-60nm. The mesopores make a major contribution to pores specific surface area and pore volume, the contribution of the micro-pores to the surface area cannot be ignored; the values of organic carbon and clay minerals are the main controlling factors of the pore development, and the influence of brittle minerals on the development of pores is not obvious.

Abstract:The Yalu River Basin is a typical multicycle and multiplex basin, which is potentially rich in oil and gas resources. Guided by the method of tectonic geology and petroleum geology and based on geophysical and geological data analysis, the authors emphatically studied Changbai Depression in Yalu River Basin and made scientific evaluation of its resource assessment according to investigating the petroleum geological condition and structure characteristics of the study area. The results show that the central extensional subsidence belt of Changbai Depression in Yalu River Basin with large thickness and continuous stratigraphic sequence seems to be the preferred favorable exploration area, which has various local structures in favorable directional zone of hydrocarbon migration.

Abstract:Dongda is located in the south of Xi'an City, Shaanxi Province. The region is of alluvial-pluvial plain and rich in geothermal resources. For the purpose of further exploration and sustainable use of geothermal resources, researchers should elaborate genetical mechanism of the geothermal field through the application of hydrogeochemical methods and analyzing regional geological conditions. The results obtained by the authors show that the geothermal field belongs to the low-medium temperature geothermal system of convective type. The regional heat flow is 74.5 mW/m2 without special additional heat source. The recharge area is located to the southwest of the geothermal field and geothermal water originates from precipitation of the Qinling Mountain with a recharge elevation of more than 1320 m. The temperature of the deepest reservoir is estimated to be 110℃, with a deep water cycling of 3120 m. The geothermal water age is about 14461 a. A number of different directions of active faults exist in the region. Under the effect of thermal convection, geothermal water flows upward along the faults and is mixed with more cold water. Because of the overlying Quaternary loose deposits, geothermal water is stored in the shallow reservoir, forming the Dongda geothermal field.

Abstract:The Dongbeigou molybdenum deposit is a newly discovered large-sized cryptoexplosive breccia molybdenum deposit in Kuandian, Liaoning Province. In this study, the authors first carried out a comprehensive study including zircon U-Pb dating, petrogeochemical investigation and Hf isotope analysis of the monzonitic granite related to the Dongbeigou molybdenum deposit. LA-ICP-MS zircon U-Pb chronology indicates that the monzonitic granite was emplaced at (129.4±0.3) Ma. Geochemically, the monzonitic granite has rich silicon (SiO₂=62.21%-83.21%), high potassium (K₂O/Na₂O=3.35-20.27), and rich alkali (K₂O+Na₂O=5.82%-12.23%), belonging to shoshonite series peraluminous granite and characterized by LREE enrichment, HREE depletion, and weak negative Eu anomaly (δEu=0.63-1.07). The monzonitic granite is enriched in LILEs such as K, Rb and Pb, and depleted in HFSEs such as Nb, Ta, P and Ti. According to zircon Hf isotope analyses, the ε_Hf(t) values of monzonitic granite are-12.4——8.5, and two-stage model ages (t_DM2) vary from 442 Ma to 1610 Ma. These characteristics suggest that the primary magma was derived from the remelting of the Mesoproterozoic crustal materials. In combination with metallogenic geological background, the authors hold that the monzonitic granite and the Dongbeigou molybdenum deposit were developed from the subduction of the Pacific Plate beneath Eurasia associated with Cretaceous lithospheric thinning.

Abstract:Located along the Sankuanggou-Duobaoshan tectonic-metallogenic belt in Da Hinggan Mountains, the Sankuanggou skarn-type Cu-Fe-Mo deposit is a typical skarn-type deposit. On the basis of field geological survey and indoor rock ore identification, the authors analyzed the lithogeochemical characteristics of Sankuanggou (granite) tonalite related to metallogeny,and discussed the genetical type and tectonic setting of this rock mass. Studies show that the magmatic rocks of this deposit belong to the calc-alkaline I-type granite, with the characteristics of continental crust, and that these magmatic rocks were formed in a volcanic arc tectonic environment or a similar environment, mainly having close relationship with volcanic arc granite orogenic phase. REE distribution patterns show LREE-enriched patterns with gently rightly inclined shape, and strong REE fractionation with no pronounced negative Eu anomaly, suggesting that these magmatic rocks have the same or similar genesis and reflect the characteristics of comagmatic region. δEu values vary from 0.81 to 1.24, δCe values range from 1.00 to 1.13, indicating that weak fractional crystallization occurred in the process of magma evolution, with some influence of assimilation and contamination, and that their low oxygen fugacity of diagenetic environment might imply some anoxic environment.

Abstract:In order to deeply study the migration regularity of element and preliminarily infer the fluid evolution during alteration processes in the Mujicun Cu (Mo) deposit, the authors tested and analyzed the samples which were respectively collected from the strongly silicified zone, the potassic zone, the quartz-sericitic zone and the propylitic zone in the ore-bearing diorite porphyrite body. Through calculation based on the formula by Grant, the authors made a tentative quantitative discussion on characteristics of the gains and losses of elements during their migration. The results demonstrate that mass migration of different elements show certain regularities within the range of mineralized alteration:(1) the initial hydrothermal fluid is rich in K and is poor in Na. Compared with least-altered rocks (the propylitic zones), the losses of Fe₂O₃, MgO, P₂O₅ and TiO₂ turn into the gains in altered rocks from deep strongly silicified zone to shallow quartz-sericitic zone, with the generally opposite migration regularity of SiO₂ and MnO, and FeO is depleted in the three alteration zones. (2) The migration regularity of rare earth elements is similar to that of Fe₂O₃ and some other components. The REE curves assume a rightly dipping REE pattern, indicating obvious fractionation between LREE and HREE, with the enrichment of LREE and the losses of HREE. (3) Cu and Mo are especially enriched in the quartzsericitic zone and also relatively enriched in the potassic zone. These data suggest that the altitude of 400-500 m in the diorite porphyrite body is the main Cu and Mo enrichment area.

Abstract:Based on field observation and microscopic and backscattered electron (BSE) images, the authors recognized a two-stage formation process of the skarn in the Nannihu-Sandaozhuang Mo (W) deposit. At the first stage, the fluid reacted with marble to form wollastonite, andradite, grossularite, hedenbergite and diopside. As the fluid migrated outward, the dark limestone was replaced by diopside skarn or wrigglite diopside skarn. At the second stage, the fluid spread into the wall rock along fractures to form new skarn which was superimposed on the earlier skarn. According to these observations, the skarn minerals such as garnet and pyroxene could be divided into two generations. The first generation of garnet Grt_I) (Gro_3-82And_15-96) is spot-like in wollastonite marble or skarn, and the first generation of pyroxene (Px_I) (Di_18-86Hd_13-70Jo_0-13) could intergrow with Grt_I in wollastonite marble or skarn and with plagioclase (Ab_55-70An_30-44) in wrigglite diopside skarn. The second generation of garnet (Grt_II) (Gro_23-58And_37-74) and the second generation of pyroxene (Px_II) (Di_0-68Hd_28-84Jo_3-16) were superimposed on GrtI and Px_I with smaller space area. The mineralization of molybdenite and scheelite commenced at the very beginning of skarnization and covered the whole skarn formation process. The local reducing environment, induced by the reaction between the fluid with adequate concentration of Mo and W elements and the wall rocks might have triggered metal precipitation.

Abstract:Lead, zinc and silver polymetallic deposits are intimately associated with the hypabyssal acidic rock mass in northern Zhangjiakou area. Middle-Upper Proterozoic carbonate strata are widely distributed in southern Zhangjiakou. Some polymetallic ore deposits (ore spots) have been found in carbonate strata, such as Liangjiagou, Huoshigou and Changzhuangzi. Dolomite formation of Gaoyuzhuang Group and Wumisan Group of Jixian System constitute the major ore-host rocks. Contrary to polymetallic deposits located in northern Zhangjiakou area, polymetallic deposit lies in the dolomite strata where intermediate-acid intrusive masses are not developed in the mining area. In addition, the orebody characteristics, ore fabric and ore deposit geochemistry have significant difference from the polymetallic deposits related to the hypabyssal acidic rock mass in northern Zhangjiakou area. Taking the Liangjiagou polymetallic deposit as an example, based on the field observation of the geological characteristics of ore deposit and ore, and taking into consideration various isotope test results for such elements as Pb, S, Rb, Sr, the authors have reached the conclusion that the sources of ore-forming material might have come from dolomite strata or substrata, the formation of the deposit was related to the large-scale overthrust nappe tectonic system, and the genetic type of ore deposit belongs to the Mississippi valley type (MVT) ore deposit.

Abstract:The Yushui copper polymetallic deposit is located in the east zone of the South China MVT (Mississippi valley type zinclead deposits) metallogenic belt. The orebody mainly occurs between the littoral quartz sandstone of lower Carboniferous Zhongxin Group and littoral dolomite of upper Carboniferous Hutian Group, with a small number of mineral veins hosted in dolomite. The ore grade is so high that the processing grade was 15.5% in 2013. The ore is mainly in massive form while a small amount of ore being disseminated. The ore minerals include chalcopyrite, bornite, chalcocite, galena, sphalerite, pyrite, hematite and magnetite, and the main gangue minerals consist of dolomite, calcite and a small amount of quartz. The mineralization can be divided into hematitemagnetite stage characterized by existence of gel texture gangue and sulfide stage. By analyzing the temperature and salinity of fluid inclusions in sphalerite and quartz from the main metallogenic stage (sulfide stage) the authors found that the fluid inclusions from the Yushui copper polymetallic deposit mainly consist of gas-liquid two phase inclusions, with the gas-liquid ratio ranging from 5% to 20%, and the homogenization temperature ranging from 90℃ to 289℃. In addition, the homogenization temperature of fluid inclusions in sphalerite ranges from 90℃ to 289℃; the homogenization temperature of fluid inclusions in quartz ranges from 110℃ to 287℃; the homogenization temperature of fluid inclusions in calcite ranges from 125℃ to 210℃, the inclusion salinity range is concentrated on 8wt%-15wt%. The laser Raman microprobe test shows that the gas composition of the fluid inclusion is H₂O with minor CO₂. Fluid inclusion study combined with geological and geochemical studies of the deposit suggests that the Yushui copper polymetallic deposit is a stratabound and epithermal deposit.

Abstract:The lithostratigraphy of the bauxite-bearing rock series of Dazhuyuan area in northern Guizhou is the upper Carboniferous Dazhuyuan Formation, which was deposited in Zhuoshui Lake in the late Carboniferous Maping stage. The lake was one of the offshore lakes in the southwest of Yu'e Bay. In the period of the early Dazhuyuan Formation, the high water lake with the area of 480 km2 was close to the coastline of Yu'e Bay. Sediments were mainly derived from the chemical deposition in the permanent low-energy shallow lake. It deposited amounts of chlorite rock, chlorite clay rock, ferruginous clay rock and a small amount of chamosite iron, hematite. In the period of the late Dazhuyuan Formation, the lake with the area of 288 km2 became shallow and small because of the augmenting of the distance between the lake and the coastline of Yu'e Bay. Then the lake became an intermittent flood control high-energy shallow lake. Huge areas of bauxite (bauxite rock) was deposited from the physical deposition.

Abstract:The Ordovician strata constitute an important target of marine potassium ore in the east of Central paleo-uplift, Ordos Basin. Based on core, logging and seismic data, the authors conducted researches on the middle combination of Majiagou Formation (from 5th to 10th intervals of the fifth member of Majiagou Formation), in the aspects of sedimentary microfacies, evaporate distribution, formation mechanism and preservation condition of evaporate. The results indicate that the middle combination of Majiagou Formation was deposited in a restricted platform environment which can be further divided into four sedimentary microfacies, i.e., tidal flat, tide marginal beach, outer lagoon and inner lagoon. These microfacies are distributed around the central paleo-uplift orderly. The inner lagoon is the main depositional environment of the potassium evaporate. The sediments of the inner lagoon present obvious cyclicity. The sedimentary environment of the sub-member 6, 8, 10 were under the regressive evaporation condition and produced evaporite and dolomite, while the sub-member 5, 7, 9 were of transgressive setting and formed limestone. In the regressive period, the centripetal enrichment effect formed a large salt sag in Mizhi area, Shaanxi Province. Furthermore, under the mechanism of"salt deposited in deep water", a lot of thick potassium evaporate series were deposited. These potassium evaporate series were mainly distributed under the post-karst basin coincidentally. The analysis of the intensity and depth of the Caledonian karst indicates that karstification did little damage to these potassium evaporate series.

Abstract:Hoh Xil in Qinghai has undergone complicated tectonic evolution and surface process since Carboniferous. Some plateau and alpine landforms were formed by these geological processes, such as high mountains, broad valleys, planation surfaces, glaciers, hot springs, rivers and lakes. In addition, Hoh Xil has preserved some geological heritages, like ophiolitic mélange zone, fault zones, earthquake sites and volcanoes. In this paper, the authors divided geological heritages of Hoh Xil in Qinghai into seven types, i.e., geological structure, volcanic systems, mountains systems, stratigraphic sites, fluvial and lacustrine systems, glaciers, and ice ages site, which constitute more than sixty sites of geological heritages in accordance with IUCN (2005), based on geological field survey and previous studies. The results show that the study of geological heritages in Hoh Xil of Qinghai has important geoscience significance in reconstructing ancient Tethys and investigating the mechanism of earthquake, the uplift process of the Tibetan Plateau and the relevant global climate change. Eight tectonic evolution stages of Hoh Xil from Carboniferous to Quaternary were recognized on the basis of geological heritages in Hoh Xil area.

Abstract:Land subsidence is one of the main geological disasters in Beijing area. In this study, the authors investigated the spatial distribution characteristics of land subsidence in Beijing area by using the permanent scatter interferometric synthetic aperture radar (PS-InSAR) technique and studied the relationship between the multiple factors of land subsidence and the deformation obtained by PS-InSAR on the GIS spatial analysis platform,. Some conclusions have been reached:(1) The land subsidence in Beijing area mainly occurs in the east, north and south of the plain, where there are multiple settlement centers, with the maximum settlement rate reaching 152mm/a. The regional uneven subsidence areas are obvious, and there is a trend that these areas are connected with each other to form a complete subsidence region. (2) The distribution of land subsidence areas is controlled by structures; the subsidence area is mainly located in the area of the sedimentary depression formed by several major active faults, which is in agreement with features of the Quaternary deposit. There is an obvious corresponding relationship between the development trend of the land subsidence and the strike of active faults. In the area of active faults, the land subsidence section line shows obvious turning or abrupt change, and the uneven subsidence on the two sides of the fault is very obvious. The layered settlement is directly proportional to the cohesive soil in the corresponding layer. The spatial distribution of the land subsidence has a good agreement with the stratigraphic structure and the thickness of the compressible cohesive soil layers in Beijing area. The range of the land subsidence area expands from the northwest characterized by the single structural zones to the southeast characterized by the multistructure zones. The areas where the settlement rate is more than 50 mm/a are mostly distributed in the area whose thickness of the compressible cohesive soil layers is more than 100 m. The settlement centers are in good agreement with the large thickness of the cohesive soil layers. (4) The second confined groundwater (top and bottom depth being 100~180 m) exploitation is the most influential factor responsible for the land subsidence, and the settlement centers are in agreement with the groundwater funnel.

Abstract:Strengthening the management and service of geological samples is an important task of the land and resources department. At present, the storage of the national geological samples is scattered, the utilization rate is low, and the information level is low, far from playing its due role. As a new generation of information network technology, the Internet of Things can be used to implement intelligent management and to achieve data aggregation and sharing. Combined with the actual situation of national geological samples, the authors analyzed the feasibility and the promotion effect of the application of the Internet of Things in the management and service of geological samples, put forward the construction method of the Internet of Things of geological samples, provided a practical solution for the intelligent management of geological samples and the integrated management and application of geological sample information.