Fengcheng, China
Fengcheng, China

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Qin X.-L.,Chang'an University | Qin X.-L.,Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits MLR | Li R.-X.,Chang'an University | Li R.-X.,Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits MLR | And 8 more authors.
Natural Gas Geoscience | Year: 2017

The Upper Palaeozoic gas reservoirs in the eastern Ordos Basin are typical tight sandstone reservoir. Petrographic observation and geochemical analysis were used to study diagenesis and diagenetic fluid of sandstone. Results show that two periods of altered mineral assemblages were formed after strong alteration. Early period of altered mineral assemblage includes kaolinite, flaky illites, sericite and quartz, which were altered by organic acidic fluid produced by thermal evolution of coal-measure source rock. Late period of altered mineral assemblage includes illite, epidote, ankerite, and idiomorphic pyriteetc. The δ13CPDB values of carbonate cement are from -1.18‰ to -11.97‰, with average of -5.57‰, and the δ18OPDB values are from -2.28‰ to -15.1‰ with average of -12.57‰. Illite and kaolinte are enriched in LREE but depleted in HREE characterized by downwards sloping and some extent of δEu and δCe anomaly. The peak homogenization temperature of fluid inclusions in late siliceous cements is 170℃, which is much higher than temperature of the maximum burial depth of strata. In early Cretaceousthe, Ordos Basin subsided. Meanwhile, a large-scale thermal anomaly event happened, which had facilitated the large scale hydrocarbon-generation of the Paleozoic coal-measure source rocks. The generated hydrocarbon fluid and hydrothermal fluid migrated into reservoir sandstone beds to alter the reservoir sandstone. Abundant of hydrothermal altered minerals were formed to fill pore space of reservoir sandstone which make reservoir compact. © 2017, Science Press. All right reserved.


Gao X.-F.,Research Center for Orogenic Geology | Xiao P.-X.,Research Center for Orogenic Geology | Kang L.,Research Center for Orogenic Geology | Zhu H.-P.,Shaanxi Geological Survey | And 3 more authors.
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2013

This paper presents petrological and geochemical features and zircon U-Pb age of a suite of bimodal volcanic rocks in the Bulunkuole Group from the Taishuihai Massif, NW China. The zircon U-Pb dating results yield a mean 238U/206Pb age of 521.3±3.3 Ma, representing the extrusion time of the dacites in the Middle Cambrian, which indicates that the previously defined Paleoproterozoic Bulunkuole Group also includes early Paleozoic volcanic rocks. The basalts and dacites belong to low-K affinities. The basalts show enrichment in Rb, Ba, K and LREE, and depletion in Nb-Ta and Th, suggesting that they were derived from a previously metasomatized depleted mantle. The dacites also show more enrichment in LILE and Th, and larger depletion in Nb-Ta, Sr and Ti in comparison with the basalts. Different REE patterns and trace element features between the two rock types, and the absence of differentiation trend from the basalts to dacites, argue against the origin for the dacites as the differentiates of the basalts. Combining the dacites geochemical features and the experimental data suggest that they are melts of lower crustal mafic protoliths heated by contemporaneous underplating basaltic magmas at relatively low pressure conditions. The occurrence of the bimodal volcanic rocks reflects that the region experienced an extensional tectonic-magmatic event during early Paleozoic. The new data suggests that the previously defined "Paleoproterozoic Bulunkuole Group" includes at least three components: (1) the Paleoproterozoic khondalite series; (2) the Indo-Sinian high-pressure metamorphic complexes and (3) the early Paleozoic volcano-sedimentary associations.


Fan L.-M.,Shaanxi Geological Survey | Fan L.-M.,Shaanxi Institute of Geo Environment Monitoring | Ma X.-D.,Chang'an University | Ji R.-J.,China University of Mining and Technology
Meitan Xuebao/Journal of the China Coal Society | Year: 2015

It is the unique geological environment conditions in northern Ordos Basin Jurassic coalfield that the issue “ water-preserved coal mining” is presented. After years of research, there have been some significant progresses in basic research and engineering practice. This paper summarized the latest achievements in the research of water-preserved coal mining. In the basic research phase: identified spatial distribution relation between coal bed with aquifers and impermeable layer; established the structure type of coal bed roof; divided the coal mining area into different partitions to protect aquifer; and specified the mining methods in different regions to protect groundwater. In the engineering practice phase: five kinds of aquifer-structure-preserved mining methods be employed to protect roof aquifer structure, including cut-and-fill mining, strip mining, slice mining, short-wall continuous mechanical mining and fast marching mining; reinforced bottom plate by grouting to protect Karst confined water in Weibei mining area; and transferred swallet into mined-out area to improve the utilization. ©, 2015, Meitan Xuebao/Journal of the China Coal Society. All right reserved.


Li C.-L.,China University of Geosciences | Yu X.-Q.,China University of Geosciences | Liu J.-L.,China University of Geosciences | Wang B.-Y.,Shaanxi Geological Survey | And 2 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2012

The Dongjikou pyroxene sysnite, appearing as irregular ovoid, intruding into the Palaeoproterozoic high-grade metamorphic rocks of Taihua group, and developing gneissic schistosity in Huayangchuan region, Xiaoqinling, is the only known Caledonian rock body. Detailed petrography and field work studies on Dongjikou pyroxene sysnite indicate that inner parts of the rock body, according to the different structural characteristics, can be divided into the earlier-formed fine-grained pyroxene syenite, developing optalic boeder and a little later-formed medium-grained porphyritic pyroxene syenite, developing chilled border. The mineral association in both types of rocks is composed of plagioclase, potassium feldspar, pyroxene, amphibole, quartz, etc. The phenocrysts are mainly composed of pyroxene and plagioclase. Pyroxene and amphibole have experienced the retrogressive metamorphism. LA-ICP-MS zircon U-Pb ages of the fine-grained pyroxene syenite and medium-grained porphyritic pyroxene syenite are (214.8±3.1) Ma(MSWD=0.48) and (212.9±3.1) Ma(MSWD=5.6) respectively, which represents that the formation age of the rock is Late Triassic instead of the Caledonian period. The isotopic dating results show that the Caledonian magmatism event was extremely weak or inexistent in Xiaoqinling area. According to isotopic dating in this paper and a systematical summary of the previous research on the geological characteristics, it can be concluded that the age of the Dongjikou pyroxene sysnite is very close to that of the Indosinian magmatic and metallogenic event in Xiaoqinling area. It's concerned that the Indosinian magmatism is related to the transition regime from oceanic slab subduction to intercontinental collision. Moreover, intensive crust-mantle interactions caused upwelling of the deep material and triggered the gold enrichment.


Fan L.-M.,Shaanxi Geological Survey | Zhang X.-T.,Shaanxi Geological Survey | Xiang M.-X.,Shaanxi Geological Environment Monitoring Station | Zhang H.-Q.,Shaanxi Geological Survey | And 2 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2015

The paper analyzed the damage situation caused by coal mining at Yushenfu coal mining area by field survey and remote sensing interpretation. The study results show: 1802 (group) fissures and 95 ground subsidence have been caused by coal mining since 1993 within a total area 94.47 km2; The distribution of ground fissures on the surface has significant zonation. Ground fissures are intensive, and seriously damage the topography at the loess donga region, however, due to their partial closure, the surface appearance is not obvious at the aeolian sand region; Mining intensity plays a decisive role in the development of fissures. Ground fissures mainly occur in the North of Shigetai-Daliuta, Dachanghan-Laogaochuan, Yujialiang, Jinjie, Ningtiaota and the area of Dabianyao-Mhuangliang where underwent high intensive coal mining activities. ©, 2015, China Coal Society. All right reserved.


Wang X.-L.,Shaanxi Geological Survey | Gao X.-P.,Shaanxi Geological Survey | Liu Y.-Q.,Shaanxi Geological Survey | Li X.-L.,Shaanxi Geological Survey | And 5 more authors.
Northwestern Geology | Year: 2010

Through regional geological survey and research, the authors consider that the Qimantage Group or Tanjianshan Group, established by predecessors, include epimetamorphic clastic rock, intermediate acidity volcanic rock and basic-ultrabasic rock in different epoch. Based on the graptolite fossil assemblage of Silurian collected in the first subgroup of formerly named Ordovician Qimantage Group at east Kunlun (it is the first time to prove that there exists Silurian strata) and isotope dating information (Yazidaban volcanics age), it is suggested that its age includes Ordovician, Silurian and Triassic etc. According to stratum guidelines and stratum cleaning, authors dismember the Qimantage Group and redefined it as Tanjianshan Group of Ordovician system (OT), Baiganhu formation of Silurian system (SA) back-arc basin flysch deposit and Yaziquan formation (Sy) island arc volcanics, Yazidaban silica rocks (Si) of carboniferous system, Elashan formation of triassic system (T3e;), Langyashan formation of the Jixianian system (Jxl) and Ayakekumu lake ophiolitic melange of Nanhua-Ordovician system C (Nh - O aΣ] . The result provides some new important evidences for the stratigraphic division and correlation, structural evolution of early-palaeozoic at Qimantage area.


Wang X.-L.,Shaanxi Geological Survey | Gao X.-P.,Shaanxi Geological Survey | Liu Y.-Q.,Shaanxi Geological Survey | Li X.-L.,Shaanxi Geological Survey | And 5 more authors.
Northwestern Geology | Year: 2010

Through research on the rock assemblage of basic volcanic rock and basic-ultrabasic volcanic rock as well as their feature on petrology, lithochemistry, trace element and REE etc, it is suggested that Heishan structural ophiolite belt is an important material component of Qimantage binding belt, which was formed gradually in the process of plate's dive-collision and connected with Nalinggele structural belt, and was the division fault between Qaidam basin and north block of East Kunlun. Comprehensive researches from isotopic dating have concluded that the Heishan ophiolite was formed in Nanhua Ordovician period and its structural location was formed in Silurian period-early Middle Devonian epoch. This paper provides new important information for the structural evolution of East Kunlun and indicates that in the Qimantage area (Qaidam basin), at the north of Heishan Structural Ophiolite Belt, generated some endogenetic deposits which were concerned with hydrothermal fluid and region metamorphism, such as copper, tungsten, titanium and iron, which were related to magmatic rocks and metamorphic rocks; and in the Kumukuli basin (the northern block of East Kunlun), at the south of Heishan Structural Ophiolite Belt, occur some exogenetic ore deposits, such as sandstone-conglomerate type copper deposits, placer gold, gypsum, and halite etc.


Yang X.,Chang'an University | Han K.,Chang'an University | Wu X.,Chang'an University | Wang B.,Shaanxi Geological Survey | And 5 more authors.
Earth Science Frontiers | Year: 2016

Intra-continental orogeny has recorded a complex geological process. The research area, Ann Kang Shiquan-Hanyin-Xunyang belt, belongs to South Qinling orogen, and lies on the convergence parts of South Qinling intra-continental compound orogen and the northern Yangtze plate. And there develops the early Paleozoic deformed metamorphic rock sheets of the Silurian system, which mainly is overthrust structure and multi-level ductile slip overthrust rock sheet. There widely produces new multi-stage foliations that can be classified into 3 stages since the Indosinian period; the foliation replacement shows distinctly, and S2 foliations replacing S1 foliations appears dominantly in the covering stratum area. Considering the following facts that the multi-stage structural deformation, the granite invasion into cap rock, the magma diapir-stretch and heat dome rising of the basement, the thermal metamorphism with the late granite veins and high temperature mineral pairs that consist of secondary enlargement biotite porphyroblasts and garnet phenocrysts, the wide development of many types of hydrothermal alteration, the differences between the temperature and pressure characteristics of the fluid inclusions in quartz veins that exist in different stage foliations, that the Ar-Ar dating of biotites along the ductile shear deformation foliations is 161-169 Ma in Shiquan area, that the Ar-Ar dating of micas along the ductile shear deformation foliations is 178-163 Ma in the northern part of Fenghuangshan dome etc., it is suggested that the research area has undergone at least the Indosinian and the Yanshanian, the two tectonic deformation periods. Particularly, S2 foliation roughly corresponds to Yanshanian period, it is typically an intra-continental orogenic structural deformation. The characteristics of plastic flow in solid state and brittle-ductile shear deformation are significant. Through the structure-petrography mapping, we conclude that the S2 foliations are predominant in the area, their strike is mainly to the northwest; most of the new minerals and rocks are distributed along the S2 foliation, those suggest that Yanshanian period have a close relation to intra-continental orogeny. The brittle-ductile shear zones can emerge in the intense portion of structure deformation. The late Indosinian-Yanshanian period has been mainly presented by the combination of folds+S2+3 foliations+overthrust faults, the Cenozoic has been shown by the fault-blocks with different degree in strike-slip and uplift. The evolution of intra-continental orogeny can be divided into three sub-stages: (1)the collapse stage in the late Indosinian-early Yanshanian period (T3-J1+2); (2)the extrusion-overthrust stage in the mid-late Yanshanian period (J3-K2); (3)the block uplifting and transformation stage in the Himalayan period. Intra-continental tectonic convergence and strike-slip induced the condensation of tectonic thermal power in the upper crust, and formed the Fenghuangshan-Niushan magma-heat dome, leading to the partial melting of crust and the invasion of granite veins. The southern part, Annkang fault belt and the northern part, Ning Shann fault belt has undergone dextral strikne-slip deformation and sinistral strike-slip deformation respectively in Yanshanian period, which formed the more distinct east extrusion slip shear deformation in the study area, showing that the strike-slip of intra-continental orogeny cannot be neglected. © 2016, Editorial Office of Earth Science Frontiers. All right reserved.


Wang X.-L.,Shaanxi Geological Survey | Gao X.-P.,Shaanxi Geological Survey | Liu Y.-Q.,Shaanxi Geological Survey | Zhou X.-K.,Shaanxi Geological Survey | And 4 more authors.
Northwestern Geology | Year: 2010

Based on (1970±47) Ma (zircon U-Pb) isotopes age data obtained from the granite-gneiss, combining petrology, rock geochemistry and region stratigraphie correlation, we dismember Kalakashi rock-group from formerly Ailiankate group. Studying on petrology, rock geochemistry, structural feature, deformation metamorphic feature, isotopes age and metallogenetic specialization, it is suggested that the basement of Tiekelike fault-uplift is a double structure basement, and the crystal basement is formed by Kalakashi rock-group, the transitional basement is formed by Ailiankate rock-group and Sailajiacitage rock-group( the Sedimentary cover is composed of Bochatetage formation and Sumalan formation of the Jixianian system, Sukuleke formation of the Qingbaikou system, and strata of Sinian system. Kalakashi rock-group is conducive to the formation of iron-copper-gold polymetallic ore deposits. This result has important significant for researching on development and evolution of Tiekelike faultuplift's crystal basement.

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