The Study Of Coal Petrology And Coal Geochemistry In Permo-Carboniferous Coal From Datong Coalfield

Datong coalfield was a double period coalfield that is composed of Late Paleozoic Permian-Carboniferous coal-bearing and middle Mesozoic Jurassic coal-bearing stratum. Following the resources of Jurassic coal is exhausted steadily, the Permian-Carboniferous coal become new explore object. At present, Permian-Carboniferpus coal-bearing stratum have got many attention from scholars, but the system study about it's coal petrology and geochemistry also is rare. So the author apply the theory knowledge and method include of coal geology, coal petrology, coal chemistry, coal geochemistry and deposition etc, further approach Datong Permian-Carboniferous 2^nd, 3^rd, 5^th, 8^th coal 's quality, petrology composition, geochemistry and coal facies characters from genetic angles. The aim is just for interpret the coal-bearing stratum problems such as coal quality and coal petrology and provide some basis for mine and application. The main conclusion is as follow:1. The Vitrinite average reflectance is 0.82%, belong to the second metamorphism period. Datong Permian-Carboniferous coal is low moisture content, rich ash and high volatilize. 2^nd and 3^rd coals are low sulfur, 5^th coal is middle sulfur and 8^th coal is high sulfur. The main composition of coal ash is Al₂O₃ and SiO₂.The coal quality pattern is gas coal and 1/3 coking coal, middle to strong cohesion, and medium coaling level. The major use is power coal and civil fire coal.2. The macro-petrographic units mainly are bright coal, dark and vitrain is secondary and fusinite is the lowest. In four coal seams, the majority of coal lithotypes is clarodurain, the durain and clarain is secongdary, vitrain is lowest. To the bottom the durain is more.In the maceral group, the Vitrinite and Inertinite content are similar, but the former is more; the Exinite is secondary and the semivitrinite is lowest. The microlithotype mainly is trimaceral, the trimaceral I in the 2^nd and 8^th coal is major and the trimaceral V is secongdary; and the distuibution situation of microlithotype in 3^rd and 5^th is opposite.There are many kind of mineral such as kaolinite, calcite, siderite, pyrite, quart, sphalerite rutile and aetite and so on.3. In each coal seam, macro elements content is lower than it's in crust obviously. Only the content of Fe from 8^th coal is higher than it's in crust.In all the discuss elements such as Mn,As,Se,Cd,Be,Pb,Cr, only the As in 8^th coal is beyond over the limitation. So should pay attention to its harm when integrated application. Through analysis we can think the Se in coal is relation to the eluviations of water and existing status of the rare-earth element, even in 5^th and 8^th it also correlations to the existing status of sulfur. The As be effected by sulfur is more than other elements, and the lowest content usually appear in the dirt partings samples, and it affected by origin sulfur more than pyrite-sulfur. The Mn in coal mainly exists in carbonas mineral and relation to organic matter and pyrite.4. In 2^nd, 3^rd, 5^th and 8^th coal there are four kinds of coal facies, they are wide waters marsh facies, wet land forest marsh facies, waters fores marsh facies and more waters forest marsh facies.