The Research Of Upper Paleozoic Metamorphism Characteristics In Northeast China

There are marine facies strata in upper Paleozoic,Northeast China, especially in the Late Carboniferous and Early Permian marine strata in the Songliao, Erlian basins are widely developed. The tectonic position of the study area is located between Siberia Plate and the North China Plate, regional structure has undergone the orogeny plate mosaic from different directions and different periods before Mesozoic, and also undergone the tectonism later in Mesozoic and Cenozoic, these show a complex tectonic evolution. Late Paleozoic volcanic-sedimentary rocks are widely distributed in Northeast China, formations are mainly marine limestone, mainly carbonate rock, a little clastic rocks, volcanic rocks, rich in fossils which contain a number of categories.According to the analysis by field, combinations of minerals, fluid inclusion thermometry, vitrinite reflectance, illite crystallinity in order to discuss the Upper Paleozoic metamorphic type characteristics, type of metamorphic facies, metamorphic grade and metamorphic phase partition Upper Paleozoic in Northeast China experienced varying degrees of thermodynamic and dynamic fields and other factors, some of later reformation is not obvious, basically remained the primary sedimentary - volcanic features; some stood post reconstruction, showing different types of metamorphic rocks, tectonite and so on. According to the transformation characteristics of these rocks in the research area, we divided four main types of metamorphism. The contact metamorphism; liquid metamorphism; dynamic metamorphism; regional low-temperature dynamic metamorphism. Based on the comprehensive identification of the samples collected in the research region, the metamorphic rocks in the area are involved in thermal contact metamorphic (no account of the role), the maximum metamorphic intensity to medium temperature, but the low-temperature contact metamorphism are still more common. The characteristics and the types of the gas-liquid alteration are very complex, the magma-liquid phenomenon is very obvious and the intensity is very strong in many Upper Paleozoic stratums in the research area. Upper Paleozoic stratigraphy and lithology changes in the region involved in gas-liquid samples primarily for low-temperature hydrothermal alteration. The characteristics of the alterations depend on the rock types. Some samples are cataclastic rock which turned from brittle rock in some fault zone of this area, but the ductile tectonism-mylonite, phyllonite, structure slate, and phyllite are the common rock types. Regional low-temperature dynamic metamorphism often has large areal or zonal distribution of the green schist facies metamorphism single-phase zone occurs in the shallow crust (typically no more than 7-8km), is a product under the strong stress deformation and low temperature conditions which turned by recrystallization and metamorphic crystallization. The regional low temperature-dynamic metamorphic rock which widely distributed in the study area can be further divided into very low grade metamorphic rocks(equivalent to low greenschist facies) and low grade metamorphic rocks(equivalent to low greenschist facies), the first three kinds of metamorphism is the regional metamorphism, the last one is the major factor about the metamorphism in the Northeast China.In this paper we identified metamorphism into very low level, low level, middle level in the Upper Paleozoic. The very low level metamorphism we mentioned in this paper means a condition which changed between no obvious diagnostic metamorphic mineral and no metamorphism, especially the mud type metamorphic rocks. The basic metamorphic rock is not developed in the research area, the rock type is dominated by the metamorphic rock which have characteristics minerals like sericite, hydromica, while the vitrinite reflection Ro is between 2.5～4.0%,illite crystallinity ranged between 0.25～0.42. That shows the undergo maximum temperature is between 200～350℃. Then we further divided the very low grade metamorphism into very low grade metamorphism A and B period. The middle-low grade metamorphism mainly in the local contact metamorphism, liquid and dynamic metamorphism zone. Besides, we can find biotite,garnet, zoisite, actinolite as the characteristic minerals, in the other hand pumpellyite and lawsonite disappear. Meanwhile the vitrinite reflectance Ro>4.0%, illite crystallinity<0.25, the maximum temperature has been subjected to >350℃.Higher degree of contact metamorphism metamorphic, liquid metamorphic, metamorphism is only partial, the metamorphic facies widely distributed in the study area can be divided into no result and sub-greenschist facies. Based on these classification of the metamorphic grade and the metamorphic mineral assemblage, we give a further description on the metamorphic facies. The study area is divided into the"overall no metamorphism(D0), the regional low-temperature dynamic metamorphism-sub-greenschist facies(D1)"two caegories. And further we divided the"overall no metamorphism(D0) into"no metamorphism"(D01),"no metamorphism-regional gas and liquid A type metamorphism"(D02),"no metamorphism-regional gas and liquid B type metamorphism(D03) there metamorphic facies area, and then divided the"regional low-temperature dynamic metamorphism-greenschist facies"(D1) into"regional low-temperature dynamic metamorphism-gas and liquid A type metamorphism(D11),"regional low-temperature dynamic metamorphism-local gas and liquid A type metamorphism(D12) and"regional low-temperature dynamic metamorphism-local gas and liquid B type metamorphism(D13) there facies areas. According to the basic parameters of metamorphic facies characteristics combined with the tectonic and environment evolution in different areas,Northeast China, through Paletology and mineral identification, vitrinite reflectance, illite crystallinity, fluid inclusion thermometry distribution characteristics, then remove rock contact zone, fault zone and other Highlevel metamorphims zone, finally we divided the Upper Pleozoic metamorphic zone into 6 types and 8 areas which are : no metamorphism area in the south of Songliao basin, Erlianhaote-Aershan no metamorphism-regional gas and liquid A type metamorphic zone, Jiamusi no metamorphism-regional gas and liquid A type metamorphic zone, Erguna no metamorphism-regional gas and liquid B type metamorphic zone, South of Daxinganling regional low-temperature dynamic-local gas and liquid A type metamorphic zone, North of Songliao basin regional low-temperature dynamic-local gas and liquid A type metamorphic zone, Daqing regional low-temperature dynamic-local gas and liquid B type metamorphic zone, east of Jilin regional ow-temperature dynamic-local gas and liquid B type metamorphic zone...