Abstract:The polycycle volcanic eruptions as well as coal and hydrocarbon accumulations seem to have been controlled by the formation mechanism of the paleorift in Nortbeast China. These were links intimately associated with each other in the geotectonic evolution processes since Mesozoic time, i.e, the crustal extension led to the volcanic eruption, the formation of faulted basins and the deposition within them of the lacustrine coal seams; later, the most intensive extension resulted in the formation of the paleorift basins and oil and gas accumulations. From Jurassic to Cretaceous, the coal accumulation was intensified with the intensification of volcanic eruption. Late Jurassic and early Cretaceous (92 -95 m.y. ), therefore, have both the strongest volcanic eruption and the largest coal reserves. Nevertheless, coal could occur only in comparatively middle or small basins while oil and gas seem to accumulate in sediments of gigantic thickness in large rift basins formed since the end of early Cretaceous. In one and the same volcano-sedimentary cycle, the coal seams were usually formed later than volcanic eruption, and were followed by the formation of hydrocarbon during the later intense tectonic evolution, these three geological events therefore formed typical temporal-spatial relationships. A sub-circular coal-bearing denuded area took shape simultaneously with the formation of the paleorift basin. The denudation, transportation and reaccumulation of coal in large quantities as well as the in situ coal-bearing beds and lacustrine putrid mud would all turn into source materials of on and gas under favorable conditions. It bas been proved that the organic chemistry of coal allows the hydrocarbon to be derived from within the coal seams. The intense geotbermal flow in the rift area has had an important bearing on the maturity of organic materials in the source rocks. For example, the geothermal values in the area of Bohai Gulf-Xialiaobe basin might have reached 9.25℃/100m in Mesozoic and 5.4-8.2℃/100m early Paleozoic. Therefore, the tectonic setting of the continental paleoxift basin, the coal-rich region and its subcircular denuded area seem jointly responsible for the formation of gigantic oil and gas fields of continental facies. Based on the foregoing discussion, the author proposes the opinion that oil and gas accumulations might be found in coal-bearing basins. Consequently, a study of paleo-structure and paleogeography of the investigated area is of vital importance.
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王东方.1984.东北大陆裂谷与中新生代火山岩的时空分布及煤、烃的构造成因关系[J].矿床地质,3(4):71~79.1984.Space And Time Distribution Of Mesozoic-Cenozoic Volcanic Rocks In Northeast China And Its Tectono-Genetic Relationship With Coal And Hydrocarbon In View Of Continental Rifting[J].Mineral Deposits3(4):71~79
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