Abstract:In the process of historical development, many researchers have done a lot of research work on the formation and evolution of each continent on the earth, but their opinions are quite different from each other. The earliest theory was continental drift, and later, there appeared the theory of sea floor expansion and plate tectonics. Based on years of research, the author believes that the six continents of the world do not drift, and it is impossible to divide the earth into several plates on a sufficient basis, because the dynamic mechanism of plate tectonics is basically reasonable. However, the basis of plate division is not enough, the boundary of each plate is not clear, and the geological differences and characteristics of each plate are not clear. Therefore, the author thinks that the whole continent of the world is inseparable, and the change of the geological period of each landmass is the result of the change of sea and land.

Abstract:The Hebukehe Formation is widely distributed in western Junggar. It is the synonym of the Hongguleleng Formation. This paper presents abundant fossils from the clastic strata which were previously assigned to the Lower Carboniferous Hebukehe Formation in Kelasaileke Mountain, western Junggar. These fossils include trilobites Phacops sp., ammonoids Manticoceras sp., brachiopods Tylothyris sp., Aulacella sp., "Mucrospirifer" sp. and Cyrtospirifer sp., plants Leptophloeum rhombicum, Syringodendron sp. and Knorria sp.. The age of these fossils is attributed to the Late Devonian. According to the lithologic association, the fossiliferous strata are redefined as the Upper Devonian Tielieketi Formation, rather than the Hongguleleng Formation. Regional geological survey reveals that the Upper Devonian of Mayili Mountain stratomicroregion is only composed of the Tielieketi Formation, without the Hongguleleng Formation. The latter is only distributed in the Shaerbuerti Mountain stratomicroregion. The boundary of the two stratomicroregions is the deep fault located in northern Mengbulake to south slope of Xiemisitai Mountain. These two stratomicroregions experienced obvious sedimentary differentiation during the Late Devonian, and gradually evolved into the evolutional stage of uniform basin environment until the early Early Carboniferous, announcing a gradual disappearance of stratigraphic regionalization of the stratomicroregions.

Abstract:The ages of rhyodacite in Jiangqiao-Nalan area of Pu'er City was determined by utilization of zircon-LA-ICP-MS in south Lancangjiang zone, and the result of U-Pb dating yielded (196.7±2.3)Ma and (198.1±3.5)Ma, which indicates that rhyolite in this area was formed in early Jurassic instead of in Late Triassic. The data fill in the record of volcanic-sedimentary activity in Jurassic's geological history. The analysis of the major elements, REE and trace elements of rocks shows that the volcanic rocks of lower Jurassic in South Lancangjiang zone were formed under the extensional tectonic background after collision, and were probably related to the subducted lithosphere plates or orogenic belt of Yamane delamination, and that they occurred after the closure of lower Cretaceous in this area were typically associated with the POG (post-orogenic granite) or A₂ granite. These data constrain the final time of Indosinian cycle. The granite has the feature of post-orogenic granite or "A" type granite, and it indicates the termination time of Indo-Chinese cycle in southwestern Yunnan.

Abstract:The exploration and development of low grade oil and gas resources which have become important alternative resources in China have made great breakthrough. Research on numerical simulation of shale gas is helpful to realizing the dynamic process of shale gas development, laying a technical foundation for understanding seepage law of shale gas, optimizing mathematical model and evaluating as well as predicting productivity. Based on intensive investigation of literature from China and abroad, this paper systematically expounds the research progress of numerical simulation methods of shale gas and summarizes advantages and disadvantages of these methods. Shale gas numerical simulation models can be divided into equivalent continuous medium model, discrete fracture network model and mixed simulation model. The equivalent continuum model is simple in principle, pursues the macroscopic equivalent, neglects the true flow mechanism inside the reservoir, and is hence suitable for homogeneous shale gas reservoirs with low development of fractures. The discrete fracture network model accurately can reflect the porous flow characteristics of complex fracture networks and describe the objective regularity of highly discrete fractures and is hence suitable for shale gas reservoirs with completed exploration and high fracture development. The mixed simulation model combines the advantages of these two models to accurately reflect the complex fracture network and fluid migration law, meet the calculation accuracy, and save a lot of computing resources. With the improvement of computing and processing capabilities, the mixed simulation model is the future development trend. Finally, various problems in the numerical simulation model of shale gas reservoir are analyzed, and the development trends of shale gas numerical simulation are pointed out.

Abstract:The composition and characteristic parameters of rare earth elements (REE) in tungsten deposits provide mineralization environment as well as fluid and source information. The achievements in the study of geochemistry of rare earth elements in tungsten deposits in China are very abundant, but it is still necessary to make a national systematic summary from the perspective of single mines. In this paper, statistics of more than 300 sets of rare earth elements of tungsten deposits in different types of deposits published from 1990 to 2016 were investigated. The results show that total REE values and distribution curves in different types of tungsten deposits are different due to different sources and ore-forming physicochemical conditions. The Eu from different types of tungsten deposits exhibits negative anomalies, which implies that the ore-forming environment was somewhat reducing. There are some interrelations between wolframite and its ore-bearing granite, However, but REE in wolframite did not enrich with magma-fluid differentiation.

Abstract:The Cuonadong dome is a newly discovered gneiss dome in the Tethys-Himalaya area of southern Tibet. Early Paleozoic augen gneiss is developed in the core of the dome. Based on field investigation, the authors conducted LA-(MC)-ICP-MS U-Pb dating and Lu-Hf isotopic analysis for two samples from the granitic gneiss. Core-mantle-rim texture is well developed in the zircons from the gneiss in CL images:the core is the inherited zircon with erosion embayed texture, the mantle is the igneous zircon with oscillatory zone, and the rim is the black zircon with re-melting metamorphic genesis. The weighted mean ²⁰⁶Pb/²³⁸U age of igneous zircon varies in the range of (500.6±2.6) Ma-(501.1±2.5) Ma, which represents the Early Paleozoic magmatic crystallized age, whereas the Cenozoic re-melting age of margin metamorphic zircon is (37.7±0.5) Ma, which represents the onset of the southern-Tibet detachment. The ε_Hf(t) values and two-stage model ages (T_DM2) of mantle Paleozoic igneous zircons range from -2.1 to +5.3 (averagely +2.2) and from 1.1 to 1.6 Ga (averagely 1.3 Ga), respectively, indicating that the source was derived from the partial melting of the High Himalaya Paleoproterozoic strata. Considering the regional Early Paleozoic magmatism and Cenozoic metamorphic event, the authors hold that the Cuonadong granitic gneiss was formed in the orogeny triggered by the Early Paleozoic Proto-Tethyan Oceanic subduction beneath the Gondwana continent, and recorded the Cenozoic post-collisional metamorphic and anatexis events.

Abstract:Diabase dikes are extensively distributed in the Tangbai area on the southern margin of the Lhasa terrane. In order to discuss their formation age, genesis and tectonic implications, the authors investigated their petrography, geochemistry, zircon U-Pb geochronology and Hf isotope. Zircon U-Pb dating yielded an age of (54±1) Ma for the Tangbai diabase dikes, indicating that they were formed in the Early Eocene. The trace elements are characterized by enrichment of LILEs (such as Rb, Sr and Ba) and depletion of HFSEs (such as Nb, Ta and Ti). Compared with typical arc magmas, Sangri Group basalts and Yeba Formation basalts in this area, the Tangbai diabase dikes have higher values of Nb, TiO₂ and Zr. Trace element tectonic discrimination diagrams show that Tangbai diabase dikes fall in intraplate basalts field, and show geochemical affinities with intraplate magmatism. The race element geochemical characteristics and zircon Hf isotopic data suggest that the diabase dikes were likely derived from enriched lithospheric mantle which had been metasomatized by slab-derived fluids during previous subductions, and mixed with upwelling ashospheric mantle. The intrusion age of Tangbai diabase dikes was close to the peak period (52 Ma) of Linzizong volcanic activity. Combined with their genesis and tectonic setting, the authors hold that the formation of the Tangbai diabase dikes was related to slab break-off of the northward subduction of the Neo-Tethyan slab ca. 54~52 Ma in age. In addition, according to the latest 3-D numerical models of continental collision and slab break-off, it is shown that the onset of India-Eurasia continental collision should have occurred at 65 Ma or earlier.

Abstract:The Bangong Co-Nujiang suture zone and its tectonic-magmatic evolution constitute one of the hottest scientific problems related to fundamental geology of the Tibetan Plateau. The Mesozoic volcanic-intrusive rocks are widely distributed in the north Gangdese belt, which is also located in southern Bangong Co-Nujiang suture zone. The petrogenesis and geodynamic setting of those rocks remain controversial. In this paper, the authors reported the newly found intermediate-basic dikes in Awengcuo area which is located at the west segment of Bangong Co-Nujiang suture zone so as to explore these problems, and detailed LA-ICP-MS zircon U-Pb dating geochronological and element geochemical studies were carried out for the intermediatebasic dikes. The basic dikes exhibit SiO₂ content of 50.03%-51.13%, Al₂O₃ content of 15.52%-16.03% with TiO₂ content of 1.22%-1.31%, MgO content of 6.12%-8.51%, Na₂O content of 3.10%-3.58%, with Na₂O/K₂O ratio of 1.73-1.87. The diorite dikes have values of SiO₂ (55.58%-56.22%), MgO (4.69%-4.64%), Al₂O₃ (1.01%-1.06%) with TiO₂ (1.01%-1.06%), Na₂O (1.55%-5.03%), and Na₂O/K₂O (1.81-3.61). The diabase veins belong to alkaline basalt series and the diorites are subalkaline-series rocks. All of their light rare elements are concentrated evidently and heavy rare elements are deficient with a right dip distribution mode of REE, slightly negative Eu anomalies and content of HREE. On primitive mantle-normalized trace element diagrams, the intermediate-basic dikes display different degrees of enrichment of LIFEs (e.g., Rb, U), relative depletion of HFSE (Nb, Ta, Ti). The zircon U-Pb dating of diorite-dyke yielded a weighted average age of (99.2±1.2)Ma, and the basic-dyke U-Pb dating yielded an age of (108.4±2.9)Ma, indicating that the diorite-dykes in Awengcuo area were formed at the late stage of early Cretaceous. The magma source region was mainly influenced by the crustal material and underwent different degrees of fractionation crystallization of mafic minerals and plagioclases when uplifting from the high magmatic chamber. The intermediate-basic dikes were generated in a contineral intraplate setting, as shown by analyzing tectonic setting, and its attitudes were controlled by the regional tectonic stress field. The tectonic dynamics background of the dikes formed in slab break-off caused asthenosphere upwelling extension during the Bangong Co-Nujiang Tethyan Ocean's southward subduction at the late stage of early Cretaceous, indicating that the Bangong Co-Nujiang Tethyan Ocean finished the subduction at 99.2 Ma at least, and the regional stress state turned from collision to intraplate extension at the late stage.

Abstract:The Xigaze ophiolite is located in the central segment of the Yarlung Zangbo Suture Zone, and its genesis and tectonic setting remain controversial. The ophiolite has a serpentinized peridotites in the lower part, and the ultramafic cumulates are absent in the mantle-crust transition zone. Small amounts of gabbro dikes with isotropic or rhythmic textures intruded into the mantle peridotites or diabase sills. The diabase sills generally intruded along the interface of the mantle peridotites or intruded into the mantle peridotites as diabase dikes. Based on studies of field relationships and geochemical features, the authors hold that, the Xigaze gabbro dikes, instead of being formed by in-situ crystallization of magma chamber in the oceanic crust, might have resulted from the intrusion of crystals-enriched magmas from magma pockets which were distributed in crust-mantle boundary and evolved in variable degrees into silicate-rich minerals. The diabase sills might have been formed from the intrusion of mafic magmas along the structurally weak boundary. The detachment faults probably resulted in the uplift and exhumation of the upper mantle which triggered the upwelling and partial melting of asthenospheric mantle. The gabbro dikes and diabase sills in the Xigaze ophiolite might have originated from small amounts of supply and discrete intrusion of magmas in a slow-spreading ridge.

Abstract:In this paper, the authors studied the comparison between lithologic assemblage and lithofacies assemblage SHIRIMP zircon U-Pb dating results and fossil chronology, and believed that the continental volcanic rocks of the former Santanghu Formation in Oetonggar area of Eastern Junggar Basin should be redefined as the Batamayineishan Formation. It is suggested that the widely distributed continental volcanic rocks at the northeast edge of Junggar Basin should be decomposed into the Batamayineishan Formation and the Santanghu Formation according to the geological age. The Santanghu Formation only represents the early Permian continental volcanic rocks. The study of chronology shows that the age of the Batamayineishan Formation in Oetolanagar is time-penetrating. The age of the first lithologic segment is (335.6±6.5)Ma, and the age of the second lithologic segment is (320.5±7.1)Ma, suggesting that the rocks belong to the late lower Carboniferous period to the upper Carboniferous period. Thus, the dispute over the lower and upper Carboniferous system for the Batamayineishan Formation has been solved. According to the comprehensive study, this set of continental volcanic rocks belongs to tectono-magmatic activities in the East Junggar tectonic belt from west to east under the background of chain suture. The residual ocean basin disappeared until the beginning of continental volcanic activity; in addition, it was affected by the tension environment on the western side and the island arc environment on the eastern side. Volcanic mechanisms, structures, and intermittent eruptions of the Batamayineishan Formation in the Oetanagar region suggest that it has petroleum geological significance.

Abstract:The Permian granitic rock near the Chaokewula Mountain in the north of Xilin Hot area are very important for the study of the structural and magmatic acitivities in eastern Xing'an-Mongolian orogenic belt. The purpose of this study is to discuss the petrogenesis and tectonic setting based on detailed investigation of petrography, litho-geochemical characteristics and zircon U-Pb chronology of the granitic rock. The rocks are mainly composed of syenogranite, monzonitic granite and orthophyre. Geochemically, the granites are characterized by rich silicon and alkalis as well as depletion of calcium and magnesium, thus belonging to aluminous-peraluminous alkali granite. The rare earth elements demonstrate a slightly high degree of fractionation, and are characterized by richness of LREE and poorness of HREE. The rocks exhibit significant negative Eu anomalies. Trace element analyses show that the rocks are enriched in Rb, Th, K, La, Ce, Nd, Zr, Hf and Sm and depleted in Ba, Ta, Nb, Sr, P and Ti. The zircon saturation temperature of rock is 802℃, with geochemical characteristics of low Sr and high Yb, showing that the rocks were formed in an environment of high temperature and low pressure. Combined with the geological and geochemical data, the authors hold that the rocks belong to aluminous A-type granite, and the sources of rocks were formed in an island-arc environment. The zircon U-Pb age of syenogranite is (275.6±1.3) Ma, and the zircon U-Pb age of orthophyre is (274.2±1.4) Ma, respectively. These results indicate that the rock body was formed in late period of early Permian. With a set of volcanic rocks of Amushan Formation as the research object, the authors obtained the zircon U-Pb age of andesite. Combined with the palaeontology, granitoids and chronological evidence, the authors consider that the Hegenshan Ocean was closed and completed the transformation from collision to post-collision during the period from late Carboniferous to late Early Permian.

Abstract:There exist different opinions concerning the petrogenesis and tectonic background of Mesozoic volcanic rocks developed in the Da Hinggan Mountains. The Late Mesozoic volcanic rocks in the Xi Ujimqin Banner of Inner Mongoliais a very important part of the huge volcanic rock belt in eastern China.The authors studied the volcanic rocks of Baiyingaolao Formation in Hanwula of Xi Ujimqin Banner in such aspects as field occurrence, petrology, zircon U-Pb isotopic geochronology and geochemisty in order to constrain their petrogenesis and tectonic background. The volcanic rocks of Baiyingaolao Formation are composed of rhyolite and volcanic clastic,which are a set of felsic volcanic rocks. The cathodoluminescence (CL) images of analyzed zircons of the pyromeride and dacite porphyry from Baiyingaolao Formation and their Th/U ratios(0.34-1.25) imply the igneous origin. LA-ICP-MS U-Pb dating shows that their ages are about(140±0.8) Ma and(133±0.7) Ma respectively, suggesting the early period of Early Cretaceous. Petrological and geochemical data reveal that the rocks belong to the high potassium calc-alkaline rock series characterized by rich Si and alkali, poor magnesium and calcium, high FeO^T/MgO ratio and low Mg^#,Nb/Ta ratio. LREE are richer than HREE.The trace element geochemistry is characterized evidently by enrichment of LILE, depletion of Ba,Sr and HFSE. All these geochemical characteristics of rocks show an affinity with the A-type granites, which were most probably formed in an extensional setting and originated from the partial melting of the crust. Combined with spacial distribution of the Mesozoic volcanic rocks, the authors hold that they were probably related to the post-orogenic extension following the closure of the Mongol-Okhotsk orogen, and were also affected by the subduction of the Paleo-Pacific plate.

Abstract:The Langshan area, located on the northeastern margin of the Alxa block, was subjected to 3 deformation stages during the Cenozoic, which produced thrust faults formed by NW-SE compression in the late Miocene, left-lateral strike-slip faults caused by NNE compression and active normal faults in the late Cenozoic. Based on peripheral Cenozoic structures around the eastern Alxa margin, the authors infer that these Cenozoic faults were related to the gradual propagation of northeast Tibetan Plateau and the readjustment of the stress field. The Langshan piedmont fault zone is now at a stage of linkup, which is compatible with the constant-length fault model with the highest slip rate in the central part. The slip rate from Holocene seems to tend to become lower relative to the slip rate since late Pleistocene. Combined with the focal mechanisms as well as geometries and kinematics of faults in and around the Alxa block, the authors tentatively propose that the Hetao-Jilantai basin and the Yinchuan basin are two different extensional basins linked by a transfer zone, in which nearly NNE-trending dextral faults are developed. The Mw >5 earthquakes within the transfer zone probably occurred on the steep dextral faults as the result of regional SW-NE compression.

Abstract:Located in the west part of North Qilian orogenic zone, the Dishuishan gold deposit is one of the altered cataclastic rock type deposits hosted in volcanic rocks. LA-ICP-MS zircon U-Pb chronology indicates that the andesitic crystal tuff was emplaced at (479.7±6.9) Ma, the granodiorite was emplaced at (426.9±6.7)Ma, and the gold bearing beresite was emplaced at (482.7±9.5)Ma, which represent the ages of ore-bearing volcanic rocks, whereas metallogenic age should be later than (426.9±6.7)Ma. The geochemical data suggest that the trace elements of volcanic rocks are rich in K, Rb, Th, and relatively depleted in Nb, Ta, P, Ti. The volcanic rocks and related mineral ores have similar chondrite-normalized REE patterns, exhibiting right-dip curve, the LREE are relatively enriched and Eu negative anomaly is weak. Combined with the trace elements and the REE characteristics, the authors infer that the volcanic rocks were formed in an island-arc setting, related to subduction of Qilian oceanic crust. The volcanic magma contaminated by the upper crust probably came from the partial melting of the mantle wedge, which had undergone metasomatism induced by the subduction fluid. The chemical composition of the granodiorite reveals SiO₂ values ranging from 67.48% to 72.68%, K₂O+Na₂O values ranging from 7.15% to 7.44%, Rittmann index ranging from 1.78 to 2.07, and aluminous index A/CNK values ranging from 0.95% to 1.19%; the trace elements show enrichment of K, Rb, Th, U and relative depletion of Nb, P Ti. The LREE are relatively enriched and Eu negative anomaly is medium. The granodiorite belongs to Na calc-alkaline series weakly peraluminous I-type granitoid, and was formed in a volcanic island-arc setting of arc-continent collision and indicated crust and mantle source. According to regional geological data, the metallogenic tectonic background of the Dishuishan gold deposit was developed from the subduction of the North Qilian ocean basin beneath Alxa land block in Early Ordovician, which formed island-arc volcanic rock, and acted as main source bed→arc-continent collision in Middle Silurian period, which formed syncollisional granodiorite after Late Silurian period, and Qilian orogeny and intraplate extension in the post orogenic stage led to the enrichment of gold.

Abstract:North China landmass is the oldest landmass and one of the largest craton massifs in the world. Bengbu uplift is a part of the North China landmass, and its initial formation of continental crust is late Archean in the time limit. With the collisions and stitching of the Yangtze platform and North China continental block, the Bengbu uplift experienced complex evolution processes. In order to further explore the Paleoproterozoic magmatic activity in the Bengbu uplift, the authors updated the data of geochronologic and geochemical analysis. Based on field observation, geochronology and geochemistry of Paleoproterozoic intrusions in this area, the authors obtained zircon U-Pb ages of (2089±44)Ma and (2133±27)Ma for Zhuangzili and Muopanshan granites. The geochemical data show that granites have high-Na and low-K significantly, and belong to the quasi-aluminum supersaturated type. They are characterized by relative enrichment of LREE with a strong Eu negative anomaly and insignificant Ce anomaly. The elements of K, Nb, Sr, P and Ti are characterized by measurable depletion, and there exists relative enrichment of Rb, Th, U, Nd, Zr and Sm. Intrusion projection points are distributed in A type granite area in the discrimination diagram of genetic type. Nd twophase age (2.37-2.84 Ga) is consistent with the age of North China Craton formed in Archean, with 2.40-2.50 Ga being the main stage. ε_Hf(t) values vary between -9.77 and +9.59, with obvious differences, suggesting the complexity of the origin of the material, and the old two-phase Hf model age (2.27-2.96 Ga) suggests that the main material was derived during Neoarchean. The tectonic environment belongs to the granite category within the plate and non-orogenic tectonic environment, which implies its extensional tectonic setting.

Abstract:There are numerous mafic rocks e.g., gabbro, diabase, basalt, pillow basalt, fumarolic-amygdaloidal basalt, in the Dahongshan area, Suizhou City, northern Hubei Province. They are mainly in the form of block structurally mixed in a set of clastic rock, characterized by mélange of exotic blocks and matrix strata, suggesting a typical orogenic belt. The mafic rocks from Dahongshan area show the features of tholeiite series, and are geochemically enriched in incompatible elements such as Rb, Ba, K, Th and U and depleted in high field strength elements such as Nb and Ta, similar to features of island arc basalts. Nevertheless, the features of flat REE patterns (ΣLREE/ΣHREE=1.41-4.48, La_N/Yb_N=0.76-4.79, Zr/Y=2.65-5.38 and Ti/V=29.19-54.97) are the same as features of mid-ocean ridge basalt. Therefore, the geochemical signatures and regional geological characteristics show that these mafic rocks should be part of MORB-like/fore-arc basalts, formed along intra-ocean arc where the subduction-initiation happened. Their parent magma was produced by the nascent depleted MORB mantle and interacted with the contribution of fluids from the slab sinking plate with decompression melting. The basalts from Nanfengya and Lulinzhai yielded LA-ICP-MS U-Pb zircon ages of (816.6±7.6) Ma (MSWD=0.47) and (813.1±4.8) Ma (MSWD=0.37) respectively, interpreted as their crystallization age. Combined with the previous research results of gabbro in Yangjiapeng (947 Ma), pillow basalt in Changhe (824 Ma), and diabase in Luling (820 Ma), it is held that mass mafic rocks were formed in Jinningian period (817-947 Ma) in the Dahongshan area. They may be the products of multi-stage intra-ocean subduction. The discrimination of Jinningian ore-arc/MORB-like basalt in the Dahongshan suggests that it experienced a certain scale of ocean-ocean to ocean-continent subduction and orogeny between Yangtze block and Tongbai-Dabie block in Jinningian period, and the two blocks might have been aggregated together in late Qingbaikou period.

Abstract:A large number of Late Mesozoic granitic plutons with dark enclaves are widespread in the coastal area of Zhejiang and Fujian Province. They are considered to be the product of large-scale crust mantle interaction and magma mixing. In this paper, the authors conducted the LA-ICP-MS U-Pb dating and obtained whole-rock geochemical data of the host granites and dark enclaves of Baihe intrusion in Tiantai area, eastern Zhejiang Province, with the purpose of exploring the geochronology, petrogenesis and tectonic implications. The results obtained show that the U-Pb zircon ages of the host granite and dark enclaves are(120.4±1.2) Ma and(120.6±1.1) Ma, respectively. They are products of the Early Cretaceous Yanshanian intrusive activities in eastern Zhejiang in a syncollisional-postcollisional environment. Geochemical analyses show that the host rocks are high-potassium calc-alkaline Itype granite, with enriched SiO₂, total alkalis, and weakly-peraluminous nature; they are enriched in Rb, Th, U and K, and depleted in Sr, Ba, P, Ti, Nb and Ta, with strong negative Eu anomaly. The dark enclaves belong chemically to partial alumina low-potassium tholeiite series, with lower SiO₂, enriched sodium, enriched LREE, relatively depleted HREE, and weak positive Eu anomaly. The Hf isotope composition of zircons from host granite and dark enclaves are all indicative of mixing of crustal and mantle materials. Based on the geochronological and geochemical data, the authors hold that the Early Cretaceous I-type granites and their dark enclaves in eastern Zhejiang were generated by mixing of mantle-derived basic magma and its induced crustal felsic magma in an extension environment which followed the Yanshanian arc-back collision.

Abstract:There has been controversy for a long time that the large-scale volcanic activity of Late Mesozioc in Zhejiang Province began with Late Jurassic or Early Cretaceous? Through zircon U-Pb geochronologic study of volcanic rocks in Longquan area of southern Zhejiang Province, a batch of high precision chronologic data were obtained. These zircon U-Pb ages are between 163 Ma to 145 Ma which were confirmed by SHRIMP and LA-ICP-MS. These data indicate that large-scale volcanic avtivity in Zhejiang Province began with Late Jurassic. According to geochemical characteristics and Sr-Nd isotope analysis, these Late Jurassic volcanic rocks belong to peraluminous and high potassium Ca-alkaline series characterized by high SiO₂, K₂O but low P₂O₅, FeOT and MgO. Due to the subduction of the Pacific plate in Late Mesozoic, the lower crust material (basement metamorphic rocks) was extensively melted and the late Jurassic volcanic-magmatic rocks in this area were formed. In addition, the authors propose defining a new rock-stratigraphic unit named" the Late Jurassic Huangmaojian Group"so as to better express and contrast.

Abstract:Mayuan is one of the important lead-zinc deposits in northern Sichuan Basin, and its mineral formation is Cambrian Dengying Formation. Field and microscope studies revealed early bitumen and sphalerite, with associated galena. The biomarker of bitumen is very similar to that of the source rocks of Gjiaba Formation. The main sources of Pb-Zn deposits and paleo-oil reservoirs are the lower Cambrian Guojiaba Formation. The Rb-Sr isotopic isochron age of lead-zinc mineralization is(486.7±3.1) Ma, probably related to the formation and destruction of the first paleo-oil reservoirs. Sphalerite and barite inclusions contain CH₄ and a small amount of H₂S, bitumen, whereas lead-zinc mineralization fluids are rich in pyrolysis products of paleo-oil reservoirs. Hydrocarbon generation, hydrocarbon expulsion, the initial transport extraction of "double source layer" in the lead and zinc elements, the first paleo-oil reservoirs and the short-term TSR produced by the reduction of sulfur and lead-zinc complex precipitation all provided the material basis, and the first paleo-oil reservoirs eventually destroyed the residual early bitumen.

Abstract:The Matoushan copper-gold deposit is located in the Kangding-Jinping mountain metallogenic concentration area. It is located in the junction of the Jinping-kangding-Shuicheng fault. It is a one of medium-size copper gold deposit in Southwest Sichuan Province. Ore bodies was presented as sulfide quartz vein, which occur in Devonian carbonated mudstone limestone and Permian metamorphic basalt. They are obviously controlled by structures. Pyrite, bornite, chalcopyrite and galena are common sulfide minerals in the ore. The observation of primary fluid inclusions of quartz in the ore and Laser Raman spectroscopy analysis show that, the ore-forming fluid of Matoushan Cu-Au deposit is a system of H₂O-CO₂-NaCl, the average temperature of fluid inclusions ranged from 108.1 to 439.1℃, and the salinity ranged from 3.55% to 22.78% NaCleq with a density ranged of 0.51 to 1.12 g/cm³, the fluid inclusions at the major metallogenic stage has the characteristics of medium temperature, medium-low salinity, low density, and rich in CO₂. The δ³⁴S_V-CDT was -4.6‰ to 8.4‰ of sulfide minerals in ores, indicating that the characteristics of S isotopic are from the magmatic; the primary fluid inclusions in quartz veins are δD=-78.8‰—-48.7‰ and δ¹⁸O_H2O=-2.1‰-9.3‰, the carbon and oxygen isotopic compositions of the dolomite are δ¹³C_V-PDB=-5.3‰-1.7‰ and δ¹⁸O_V-SMOW=19.4‰-25.9‰, which indicates that the ore-forming fluid is magmatic water-mixed with meteoric water and formation fluid. Based on the geological features of ore deposit, fluid inclusions and the isotopic evidence of S, C, O and H, it can ben concluded that the Matoushan coppergold deposit belongs to the type of medium-low temperature-magmatic hydrothermal Cu-Au deposit.

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