Products of Combustion of the Yan′an Formation Coal Seam and Their Characteristics in the Northeastern Ordos Basin

The combustion metamorphic events of coal seams are a common geologic feature throughout the world,but there is no systematic study given in the product of combustion of coal seam.The coal seams in the Yan′an Formation of Northern Ordos Basin suffer spontaneous combustion universally during terrestrial time,and this study mainly focuses on the characteristics of the products of combustion metamorphic events in this area.The result shows that the burnt products contain burnt remnant coal,coal ash and burnt rock.These burnt products of combustion metamorphic events distribute with an obviously zonation in section.Compared with the primary rocks(i.e.coal,mudstone,sandstone),their petrophysics and geochemistry features vary with thermal activity,so they can be recognized as a special kind of metamorphic rock.