The Characters Of Coal-bearing Formation And Coalfield Prediction Of Ceshui Formation Of Carboniferous In Middle Hunan

The coal-bearing formation of Ceshui formation of Carboniferous in Middle Hunan is an important coal-bearing formation at the time of coal accumation at early Carboniferous in China, which is one of the coal measures with the best coal character at earl Carboniferous in South China. In order to enhance the reserves of coal resource in Hunan province, a further step research of coal geology in Middle Hunan is needed, sum up the characters and the regularities of distributions of coal measures of Ceshui formation, guide the new work of searching for coal resource, with the hope of some break through.The paper is established in the Ceshui formation of Carboniferous in Middle Hunan, through field investigation and integrated study of Stratigraphy,Petrology,Sedimentology,Geochemistry,Coal geology and Coal petrology, roundly analysised the sedimentary characters of Carboniferous and the characters of coal-bearing formation of Ceshui formation, basicly found out the coal-controlling factors and the coal accumulation of the coal-bearing formation of Ceshui formation, provided scientific reasons for predicting coalfield and choosing good coal-bearing region, especially carried out coalfield prediction on the distribution regions of rich coal and old diggings. The main understanding as below.1. The sedimentary environment of Carboniferous has experienced a process of marine transqression-marine regression-marine transqression and three different kinds appeared. One is terrigenous clastic rock environment, the second is carbonate rock environment, the third is the mixed environment of terrigenous clastic rock and carbonate rock. The main sedimentary environment is limited shelf-lagoon at early Carboniferous, thereinto, Shaodong and Ceshui formation are coastal-lagoon environment and it changed to be open shelf environment at late Carboniferous. The gesso is thought to be formed in the environment of supralittoral Sabkha.2. The parent rock of Ceshui coal-bearing formation is related with granite. The Ceshui coal-bearing formation can be divided into three periods, as frontal coal-forming period,coal-forming period and post coal-forming period, according to the change characters of each geochemic index in the profile of Ceshui coal-bearing formation. It is a marine transqression process since the top of Shidengzi formation to frontal coal-forming period, the ancient salinity is half salt-salt waver and the pH is neutral-acid at the time. The sea level is steady at coal-forming period, with half salt and acid-neutral water. The whole trend of sea level is gradual marine regression, with salt-half salt-fresh and alkaline water.3. The interluded fold zones formed at Caledonian-Indosinian in Middle and South Hunan have a dominant control action to the formation and transformation of Ceshui coal-bearing formation, and the upheavals and depressions of sub tectonic unit directly control the developmet of coal measures and coal-bearing characters, Generally speaking, which are good in the depressions and relatively bad in the upheavals. The development of paleoteconstruct and paleogeograpy have an influence to the coal accumulation at early Carboniferous.4. The depressions in the margin of ancient land are main locations of coal measures sediment and coal accumulation. Lagoon and tidal flat environment are good locations for coal measures' developing. Tidal flat with many tidal channels environment with low and middling energy are much better for coal-forming. The coal-bearing character has some relations with lithological association and the ratio of sandstone and mudstone, which is 1/2-1 in good regions. Deuteric constructs have important coal-controlling action and rich coal region generally located at rising end and gently flank of syncline.5. According to the coal-controlling action of construct and paleogeography and the rule of coal measures, combining the data of coalfield geology and mine development, have carried out coalfield prediction on the distribution regions of rich coal and old diggings-the deep part of Jinzhushan digging and the deep part and two flanks of Limin mine in Zhadu diffing. The predicted reserve of the former is 12.468 million tons and the latter is 24.830 million tons, total is 37.298 million tons.