查看更多>>摘要：The Erguna ductile shear zone is situated in the Erguna Massif,which has been exposed along the eastern bank of the Erguna River in northeastern China. The authors present comprehensive study results on the macro-and micro-structures,finite strain and kinematic vorticity,quartz electron backscatter diffraction (EBSD) fabrics,and geochronology of granitic rocks in the Erguna ductile shear zone. The deformed granitic rocks have experienced significant SE-trending dextral strike-slip shearing. Finite strain and kinematic vorticity in all deformed granitic rocks indicate that the deformation is characterized by simple shear-dominated general shearing with S-L tectonites. Mineral deformation behaviors and quartz C-axis textures demonstrate that the deformed granitic rocks developed under greenschist to amphibolite facies conditions at deformation temperatures ranging from 450 to 550 ℃. New LA-ICP-MS zircon U-Pb ages indicate that these granitic rocks were formed in Early Triassic (～248.6 Ma) and Early Cretaceous (～136.7 Ma). All the evidence indicates that this deformation may have occurred in Early Cretaceous and was related to the compression resulting from the final closure of the Mongol-Okhotsk Ocean.
查看更多>>摘要：The Longgang Block is one of the most important parts of the eastern North China Craton,characterized by extensive Late Neoarchean (～2.5 Ga) granulite facies metamorphism. However,it remains uncertain whether it was influenced by Paleoproterozoic magmatism-metamorphism. The authors provide a comprehensive analysis of amphibolite in Laojinchang area,southern Jilin Province,through petrographic,geochemical,mineralogical,and zircon dating. The main findings are as follows:The mineral assemblage of amphibolite is Hb+Pl+Cpx+Bi+Kf+Q,characteristic of amphibolite facies;zircon U-Pb dating indicates that the metamorphic age of amphibolite is 1834±33 Ma;the amphibolite has geochemical characteristics of calcium alkaline,with depletion of Nb,Ta,Ti and P. The plagioclase in the amphibolite is oligoclase,belonging to acidic plagioclase. It is speculated that the protolith of the amphibolite is diorite;using geothermobarometer,the peak metamorphic P-T conditions of amphibolite are determined to be 536-593 ℃/3.4-5.0 kbar,and the post-peak conditions are 429-566 ℃/1.3-3.1 kbar. The above results indicate that the Paleoproterozoic metamorphism has been superimposed on Longgang Block,linked to a new orogenic event on the northern edge of North China Craton.
查看更多>>摘要：Volcanic oil and gas reservoirs are generally buried deep,which leads to a high whole-well coring cost,and the degree of development and size of reservoirs are controlled by volcanic facies. Therefore,accurately identifying volcanic facies by logging curves not only provides the basis of volcanic reservoir prediction but also saves costs during exploration. The Songliao Basin is a 'fault-depression superimposed' composite basin with a typical binary filling structure. Abundant types of volcanic lithologies and facies are present in the Lishu fault depression. Volcanic activity is frequent during the sedimentary period of the Huoshiling Formation. Through systematic petrographic identification of the key exploratory well (SN165C) of the Lishu fault-depression,which is a whole-well core,it is found that the Huoshiling Formation in SN165C contains four facies and six subfacies,including the volcanic conduit facies (crypto explosive breccia subfacies),explosive facies (pyroclastic flow and thermal wave base subfacies),effusive facies (upper and lower subfacies),and volcanogenic sedimentary facies (pyroclastic sedimentary subfacies). Combining core,thin section,and logging data,the authors established identification markers and petro-graphic chart logging phases,and also interpreted the longitudinal variation in volcanic petro-graphic response characteristics to make the charts more applicable to this area's volcanic petrographic interpretation of the Huoshiling Formation. These charts can provide a basis for the further exploration and development of volcanic oil and gas in this area.
查看更多>>摘要：The basin marginal fault system is the key to understand the formation and evolution of Songliao Basin. In order to investigate the influence of marginal fault system on the structural evolution of Songliao Basin,a comprehensive study was conducted on Shiling Town and Zhuanshanhu area of Yehe Town in Siping City of Jilin Province,where is the southeastern margin of the Songliao Basin and there are a series of well-exposed fault,fold and intrusive bodies belonging to the main marginal fault system of the Songliao Basin known as the Jiamusi-Yitong (Jia-Yi) fault zone. Through profile measurement and field investigation,samples with various lithologies and distinctive features were collected. Detailed field and laboratory works include component and microstructure analysis of these samples,rock-rock contact analysis,main strike measurement and statistics analysis. These data reveal the structural characteristics of the fold,fault and intrusive bodies in the study area. The research results show that the folds are distributed in the Mesozoic strata near the main fault of the eastern branch of the Jia-Yi fault zone,and the folded strata involve the Cretaceous Denglouku and Quantou formations. In addition,the section is dominated by high-angle strike-slip thrust faults. Light-colored veins and dark-colored veins are extensively distributed in the exposed granites. Statistical analysis of joint and fault attitudes in the study area reveals a right-lateral strike-sliping along the main fault. The large-scale right-lateral strike-slip and thrust fault system in Shiling Town occurred in right-lateral transpressive stage in Late Cretaceous. Based on the results above,tectonic evolution sequence in Shiling section of the Jia-Yi fault zone during the Mesozoic can be divided into five stages:Middle Jurassic left-lateral ductile strike-slip stage,Late Jurassic compression stage,Early Cretaceous tension stage,Early Cretaceous extension stage and Late Cretaceous right-lateral transpressive stage. These may have important constraint on understanding the Mesozoic evolution of the Songliao Basin.
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维普