滇东田坝黔西土城晚二叠世煤系上段煤岩特征及煤相分析

PETROGRAPHIC CHARACTERISTICS OF COAL AND COAL FACIES ANALYSIS OF THE UPPER MEMBER OF THE LATE PERMIAN COAL FORMATION IN TIANBA AND TUCHEN

本文通过滇东田坝黔西土城晚二叠世煤系上段沉积相、煤层特征和煤岩煤质的综合研究,系统分析了区内煤层形成时的沉积环境.按成煤的古地理位置分为上三角洲煤相和上、下三角洲过渡带—下三角洲煤相两大类型.根据成煤的原始质料、结构构造、煤岩特征和成煤前后环境,详细划分出八种泥炭沼泽相.着重探讨3号煤层形成时的泥炭沼泽相特征及其变化.

The upper member of the Late Permian coal formation is a set of shallow water delta deposits in studied area. The sedimentary environments of the coal seams belong to three facies . In the upper member of the coal formation there are ten coal seams and the main seams are number 3. 6 and 12. The layers of the coal seams are stable. Their thickness varies obviously and the structures are from simple to complex. The anamal and plant fossils are contained both in seam tops and floors. There is 1-2 clayrock with cash in the seam. The coal seams contain: water (Wf) 0.81-2.47%, ash (A8) 9.16-26.42%, volatile (Vr) 26.47-41.63*5, gelatinlayer (Y) 8.0-42.5mm, the total surfur content (SQ8) 0.103-3.935%. The R癿ax of the vitrinite (0.76-1.11%,) shows that the metamorphic grade of the coal is II-IIIstage. The coal -forming matters are mostly gelatificated, so that thick cell-walls are common. The maceral mainly consists of the nonstructural gelatinized matrix and vitrain . Barkinite , cutinite and sporinite are commonly seen . Fusain and xylovitrain-fusain are locally gathered as lens . Also there are a certain amount of transitional macerals in the coal. All of the macerals can be found in broken and crumbled occurences ect. The occurcnces of mineral impurities in the coal which assume as clastic, nodular, filled and lenticular forms are comples and variable. The peat swamp facies which formed the main coal scams are unstable environments covered by relatively deep water, in which the water level and medium properties are changable . The peat swamp faeies in the studied area belong to two types of coal facies: The upper delta facies and the coalffacies from upper-lower delta transitional zone to lower delta . In accordance with genetical marks, The peat swamp facies can be subdivided into eight kinds. The coal seam number 3 is a good example to show the characters and changes in the peat swamps facies as it was forming.