A Discussion on the Structural Heredity of Coal-bearing Basin and Sandbody's Control on Coal Ash Composition

From the viewPOint of dynamic stratigraphy,and on the basis of series (55 sheets) isopach maPS of coal seam and sandbody in the coal region of Hou County, Shanxi, this study reveals that the prOCess of the development of coal-bearing basin's structure is very clear and is of obvious heredity.Form Benxi annnd Taiyuan age of Late catboniferous Shanxi age of Early Permian, the arrangement direction of all sedimentary bodies in this region is NE-NEE.It is well observed not only on the sand bodies with better orientation, but also on the limestones with worse orientation.This paper introduces 4 isopach maPS, indicating the arrangement of Benxi limestone and sandstone,Taiyuan sandstone under cpal seam No.11 and limestone K₂, K₃, K₄, Shanxi coal seam No.2 and sand they under coal seam No.2.On the basis of the heredity of coal-bearing basin's structure development the derailed analysis and correlation of lotS of isopach maps of coal seam ash content and the isopach maPS of the thickness of sand body under each of the coal seam reveal that the areaof hasher ash'content in all coal seams and the area of each underlying sand they with greaterthickness are in staggered position, in other words, the former is on the thinner belts of the latter or on the POints of disapperance of the latter, for example, the main workable coal seam No.10 and No.11 in the lower pert of Taiyuan FOrmation, the main workable coal seam No.2 and the partly workable coal seam No.1 and corresponding underlying sand theies are the cases.This relationship is even discovered in foreisn reference, for example, in 2 maPS cited by Galloway (1983) fromGairneros(1980), which were redrawn by the authors.It is suggested that the abated relationship depend on the difference of mini relief caused by the existence of underlying sand they in the opt-forming swamp, and the difference of mini relief caused the difference of underground water debit, which flowed through the swamp and brought the fine suspension of clast into it.As for the majority of sand theies and coal seams in the environment of the fluvial channel and the distributary channel of delay, the flood basin beyond the sand body hed a lower relief, so that the groundwater debit, which flowed through the swamp, was greater,and the suspension of clast,which was brought into the swamp, was also more.As discussed above that in these environments the area with thicker coal seam and with thicker sand body are arranged in staggered position, so that in such a case coal ash content in thicker coal seam is higher than in thiner coal seam.As for the coal seam formed on the basis of tidal flat barrier the thicker belt of coal seam and the underlying thicker sand body are in superimPOsed POsition.But in this case high ash content area was located in the place with lower relief far from the tidal flat barrier, where the groundwater debit was greater.The difference in the latter environment is that the higher ash content and underlying sand body by all appearance will have positive effect on the prediction of coal ash content in coal prospecting and is a useful auxiliary mark for the environment recognition.