TONSTEINS AND THEIR ROLE IN THE FORMATION OF THE PETROGRAPHIC COMPOSITION OF COALS

Abstract

The tonsteins were found in the coal seams of all divisions of the Carboniferous deposits of the Donbas. They are thin clay interlayers of kaolinite composition and, according to most researchers, are of volcanic origin. The object of this study is the tonsteins of the Lower Carboniferous deposits of the Western Donbas. Analysis of the chemical composition of the ton - steins indicates their predominantly kaolinite composition. The aluminosilicate modulus (Al2O3 /SiO2 ratio) for tonsteins from a number of mines of the Western Donbas is close to the kaolinite norm (0.85). The titanium modulus (TiO2 /Al2O3 ratio) indicates that the tonsteins of the c11 seam were formed from volcanic ash of intermediate composition (titanium modulus 0.02-0.08). The tonsteins of all the other underlying layers studied (from c1 to c8low) were formed from acid volcanic pyroclastics (titanium modulus less than 0.02). In order to establish the role of the tonsteins in the formation of the petrographic composition of the coals adjacent to them, the coal seam c11 is considered. Comparison of the weighted average contents of vitrinite (in %) for the coal patches located under and above the tonsteins showed the absence of any regula - rity in the distribution of microcomponents in the coal. Reconstruction of the conditions of peat accumulation of coals according to their microcomponent composition confirmed that the role of tonsteins in the formation of the petrographic composition of the coals of certain deposits should be assessed taking into account the specific conditions of the accumulation of paleo-peat bogs.