MINERALOGY AND GEOCHEMISTRY OF TONSTEIN FROM COAL SEAM NOVY-1A, KHARANOR DEPOSIT (ZABAYKALSKY KRAI)

The relevance of the work is conditioned by the need to clarify the role of pyroclastic material in the formation of coal-bearing deposits and the geochemical background of rare elements in coal. The main aim is to discover the nature of tonstein from the Novy-1a coal seam of the Kharanor brown coal deposit. Objects: coal and tonstein of the Novy-1a coal seam from Kharanor coal field. Methods: sampling of the Novy-1a coal seam at the Kharanor coal deposit; chemical composition was determined by inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES), instrumental neutron activation analysis (INAA); mineral composition was studied by optical microscopy, scanning electron microscopy, X-ray diffractometry. Results. As a part of the study, tonstein from the Novy-1a coal seam at the Kharanor brown coal deposit was investigated. Mineral composition, structural-textural and geochemical features of tonstein allowed us to establish its altered volcanic genesis. A set of criteria made it possible to determine the composition of the initial pyroclastic material from which tonstein was formed. We established that the studied tonstein was formed from ashes of trachydacite composition. High concentrations of rare trace elements in coal are confined to contact zones with tonstein. The highest concentrations in the contact zones were noted for REE, Zr, Nb, Y, Ta, Hf, Th and U. List of chemical elements and their concentrations in tonstein and in coal ash on contact with the interlayer confirm the conclusions about the nature and initial composition of the pyroclastic material that formed tonstein.