华北地区南部晚古生代煤的变质成因——地下水热液对煤变质作用影响的进一步探讨

GENESIS OF COAL METAMORPHISM OF LATE PALEOZOIC COALS IN THE SOUTH OF NORTH CHINA -A FURTHER APPROACH TO THE EFFECTS OF THERMAL GROUNDWATER ON COAL METAMORPHISM

在分析造成华北地区南部晚古生代煤变质分带性的地质因素基础上,阐述了煤变质成因与区域构造格局演化的密切联系;从古地热异常形成机制出发,着重讨论了地下水热液对煤变质作用的影响,建立了煤的地下水效液变质作用地质模式;用古地热-煤变质系统的概念,根据热源、载热体和通道、聚热体3个要素的配置,分析了煤变质成因。

There are some complex genetic types for coal metamorphism of Late Paleozoic coals in the south of North China. It is not to be expected to establish a unique pattern for several genetic types. Based on the assessment of the geological factors which cause the zonation of coal metamorphism, the genesis of a vast extent of higher anthracite in western Henan can not be explained reasonably by any traditional models of coal metamorphism. Having considered the relationship among the coal metamorphism, evolution of the deeper earth's crust structure, characteristics of regional tectonics and mechanism of formation of geothermal anomalies, one could conclude that thermal groundwater had deeply influenced the formation of anthracites of western Henan. There might exist a complet set of geological factors for the thermal groundwater metamorphism of coal in western Henan, such as the secondary rise of the Moho and production of intermediate magma chambers, intersection of deep faults and development of open fractures in the covers, and transfer of heat energy by thermal groundwater circulation. Heat diffusion dominated by the circulation of heat-earring fluids, a fact that should be thought highly, must be favourable to forming a profound effective anomalous paleogeothermal field.The three elements-heat source, heat-bearer and path-way and heatcollector-are comprised in a system of paleogeotherm-coal metamorphism. The effects of these factors depended on mutual superimposition, compensation or conditioning of the three factors under different geological conditions. According to the notion of the system of paleogeotherm-coal metamorphism, there are the western Henan, subregion of thermal groundwater metamorphism the Yongxia-Huaibel subregion of magmatic thermal metamorphism and the Pingdingshan-Huainan, subregion of burial metamorphism, which respective correspond with a system of convective paleogeotherm-coal metamorphism, multitudinous saparated system of conductive paleogeotherm-coal metamorphism and a norma system of which temperature increase with the normal geothermal gradient.