华北晚古生代成煤环境与成煤模式多样性研究

华北晚古生代聚煤盆地存在活动体系成煤环境和废弃体系成煤环境。前者的海相成煤环境主要为泻湖泥炭坪,陆相成煤环境以三角洲平原沼泽意义最大。晚石炭世至晚二叠世,海相为主的成煤环境逐渐被陆相为主的成煤环境所取代,由盆缘到盆内成煤环境总体呈环带状展布。成煤环境差异性影响了成煤特点,这些成煤特点成为识别海、陆相煤层的显著相标志。华北晚古生代聚煤盆地在时间上和空间上存在成煤模式的多样性,以陆表海滨岸成煤模式、废弃碎屑体系成煤模式和浅水三角洲成煤模式为主。

STUDY ON DIVERSITY OF LATE PALEOZOIC COAL-FORMING ENVIRONMENTS AND MODELS IN NORTH CHINA

The Coal forming environments of both the active and the abandoned depositional systems existed in coal accumulating basins in North China during Late Paleozoic, with many medium thick and thin coal seams formed in those active systems and the thick coal seams developing in large area mainly formed in those abandoned systems. The coal seams in Benxi Formation and most of those in Taiyuan Formation were formed in the marine environments, of which the lagoon peat flat is major type related to the active systems. The coal seams in Shanxi and Xiashihezi Formations as well as part of Taiyuan Formation were formed in the limnic environments, of which the delta plain swamp was the most important type for coal forming. Under the regressive background in the half graben basin, the coal forming environments show the following regular distribution and evolution: swamps of fan rim, back bank and lakeshore mostly distributing along south margin of the Yinshan old land and the periphery of Funiu old land, delta plain swamps mainly in the south part of the basin, peat flats mostly in the north part of the basin, and delta plain swamps and the peat flats alternately in the middle part. From Late Carboniferous to Late Permian, the majority of the marine coal forming environments were gradually replaced by the limnic ones. Between the marine and limnic coal forming environments,there are remarkable differences in water medium, plant ecology, paragenitic organism, controlling micro environment factors, associated environments, etc., which affect characteristics of coal formation. The compositions of macerals, minerals, organic components and element composition, sulphur content and occurrence, organic geochemistry, shape of coal body and sequences containing coal seams are effective facies remarks to recognize the marine and limnic environments. There are time and space diversities for coal forming models of coal accumulating basins in North China during Late Paleozoic. Three main models are summarized in the paper: 1)the epicontinental littoral coal forming model, the coal seams of Benxi Formation and the most of Taiyuan Formation being formed mostly in the middle and the north parts; 2)the abandoned debris coal forming model, the main coal seams in Taiyuan and Shanxi Formations being dominantly formed covering the most areas of the basin; and 3)the shallow delta model, the most coal seams in Shanxi and Xiashihezi Formations being formed mainly in the south and the middle parts.