| The main factors of the coal metamorphism are temperature, pressure and time, and the temperature is one of the most important factors among them. Late Paleozoic Permo-Canboniferous was an important coal accumulation period in North China where was rich in coal resources with variety coal type and regularly distribute. Therefore it could provide the natural area and abundant information for the study of coal metamorphism. Research on the coal metamorphism in Northern China has a history of nearly 100 years. In the early 1920 s, anthracite belt distributed in Jincheng and Gaoping areas where is located in the west of Jiyuan and south of Shanxi province. The geologists thought metamorphism of the anthracite were the result of comprehensive metamorphisms which included the dynamic metamorphism, regional metamorphism and the contact metamorphism. In the 1930 s, coalfield geologists were more emphasis on the dynamic metamorphism of coal. In the 1940 s, geologists from Soviet union focused on some big coal fields in China, and they claimed the main metamorphism of coal was plutonic metamorphism rather than dynamic metamorphism. In the early 1950 s, the former coalfield geologists can't use plutonic metamorphism, a universal standard, to explain China's coal metamorphism, because the coal rank of Paleogene –Neogene coal seams in Liaoning province also reached to the stage of long-flame coal- gas coal. Then, in 1956, Professor Wang Zhuquan summarized the law of coal metamorphism in North China, and put forward igneous rock metamorphism and hold the view that magmatic metamorphism played a leading role in the process of coal metamorphism. This view got a lot of supports, such as Wu Yurong who accepted that contact metamorphism play the main role on coal metamorphism in east of Northern China. There's no dynamic metamorphism. Previous opinions provide new ideas for further research.From late 1970 s to 1980 s, the formation mechanism and process of the coal metamorphism belt with EW-trending in Henan Province has been oft discussed. There are many theories and viewpoints, such as plutonic(burial) metamorphism, magmatic metamorphism and hydrothermal metamorphism. Then, the research of coal metamorphism in this area has been gradually replaced by the heat topic about the coal bed methane and shale gas exploration.It has been found that,in the south margin of the North China plate, centered around Jiyuan-Kaifeng-Yongcheng, there was a NWW-trending high rank coal belt, to the north side and south side(or to all around) that the coal rank decrease. Through the research about the metamorphism of coal belonged to the Permo-Carboniferous in Henan Province, there proposed some metamorphism such as the regional magmatic metamorphism, hydrothermal circulation and plates tectonic model. Further more, there were some different views about the formation age of the high rank coal belt, some claimed that formation age was Indosinian, but some supported in Yanshanian. There is no unified view about the issue. And for formation mechanism of the high rank coal belt, some people think it caused by the magmatic activities in Yanshanian, but some believed to be associated with the collision of the North China plate and the Yangtze plate in indosinian, there were also some people think it caused by fracture and atmospheric precipitation hydrothermal(water) cycle.From the former People's discussion, It was not difficult to find that differernt arguments were almost limited in Henan Province. Therefore, maybe there were more benefits if the study scope expanded. Since 1990 s, in the process of oil and gas exploration, Large number of igneous rock have been revealed, which intruded into the Carboniferous Permian layers. There were continuously reported and also got many achivements. In addition, many people discussed the tectonic conversion in the Indosinian and Yanshanian, when the trending of tectonic line changed from E-W to NE or NNE. The direction of tectonic line in Yanshanian was the same as the distribution trending of the magmatic rock, while the high rank coal belt distributed in different directions. Few people concerned about this issue.In view all aboved, based on these aspects of coal petrography character, molecular structure of coal, coal maceral and vitrinite reflectance and so on, the paper used the vitrinite reflectance to estimate the paleotemperature and studied the distribution and age of the magmatic rock, in particular the tectonic conversion of the Indoninian and Yanshannian period in order to discussed the feature, formation mechanism of the coal metamorphism in the southern margin of North China plate.This thesis studies the following aspects:(1)The thesis collected coal samples of the 21 coal seam systematically from the southern Pingdingshan to the North Anyang Hebi. These samples were characted by the maceral, vitrinite reflectance and XRD analysis. The paper also collected vitrinite reflectance data previous published by others scholars, then draw the map of coal metamorphism in the the southern marigin of the North China plate and detailed analysed and extracted the coal metamorphism information which reflected by itself of coal.(2) Using the vitrinite reflectance data, the thesis simulated the maximum palaotemperature with the Karweil method and Barker empirical formula in order to exact the palaotemperature field of the southern marigin of the North China plate(3)Based on the systematic investigation and collected of the previous data about outcrop in field, drills revealed magmatic rocks, the paper drew the distribution map of the magmatic rock in the study area and also discussed its peak age of magmatic activity, geochronology, intrusive period.(4)Thesis also studied on the response characteristics of the collision of Yangtze plate and North China plate in Indosinian. It included development of the foreland basin, the Songji uplifted in the eage of plate, and crustal got thinner under the force of tension, which caused by collision. In Jiyuan Kaifeng area, Triassic deposited as thickness as 3800 m and in some depression in continuous deposits of the Jurassic sediments.(5)The relationship of distribution direction of consistency between the Indosinian tectonic framework and direction of tectonic line and high rank coal belt has been studied. Then, combined with region background of the collision North China plate and Yangtze plate, the thesis aimed to construct the relation between the plate collision and the formation mechanism of coal metamorphism.(6)Conversion of the tectonic regime in Indosinian and Yanshanian in the east of Northern plate and the NE-NEE trending characteristics of the magmatic rock in Yanshanian, the thesis discussed their mutual relationship.Based on of the above research, the thesis got the following results.(1)From the southern Pingdingshan to Northern Anyang-Hebi, there were many mirco-structures, affected by the magmatic actions, could be seen in the coal samples, such as meso-sphere, pore, mosaic structure. In Huainan, Huaibei and Xuzhou magmatic actions were common phenomenons, which could reflect influence of Yanshanian magmatic actions in the role of coal metamorphism. However, the distribution of Yanshanian magmatic rock mainly limited to Tanlu fault and fracture of the Taihang Mountains area, and distribution direction was NE-NEE trending, which was inconsistent from the trend of the high rank coals. Therefore, there was no obvious relationship between the high rank coal formation and Yanshanian magmatic actions.(2)Tectonic line direction in Indosinian was nearly EW. Maximum thickness of Triassic was consistent with the distribution of high rank coals. By the palaeogeothermal simulation, thesis found out geothermal of regions was abnormal where the high rank coal distributed. All of these could reflect the high rank coal belt formed in Indosinian period. It is results of the lithosphere thinning.(3)It was easy to find the outcrop of the Magmatic rock of Yanshanian in the southern margin of the North China plate, particularly in in Qinling Dabie orogenic belt where was next to the Pingdingshan coal field and Huainan coal field. The main coal metamorphism types in these two coal fields were plutonic metamorphism. This was one of the fact to certify the limited effects of the magmatic rock to the nearly EW trending coal metamorphism in southern margin of the North China plate and it only changed parts of the coal metamorphic pattern.(4)Permo-Carboniferous coal seams had experienced multi-metamorphism. In Indosinian period, the NWW trending high rank coal belt formed. In the NE-NEE trending of Tanhang Mountains and Tan Lu fault area, magmatic actions in Yanshanian only changed parts of the coal rank and the coal metamorphism finished In Himalayan.(5)Based on these studies, the model of coal metamorphism under the tectonic regime of Indosinian was established. |
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