Petrographic,chemical and trace-elemental composition of the coal of Sohagpur coalfield,Madhya Pradesh,India

The Sohagpur coalfield is a remnant of the Son valley basin of Gondwana deposition and can be subdivided into three major subbasins from west to east: Rungta-Amlai, Kotma and Bijuri. Thick coal seams occur in the Barakar Formation (Lower Permian) and are being worked extensively.Petrographic, reflectance, chemical and trace-elemental studies on samples of coal representative of the coal seams of the different subbasins have been carried out, and the results are presented here. Petrographically, the coals of one subbasin are different from those of another subbasin and are mainly composed of vitrinertite I, and vitrinertite V, that alternates with fusite. Vitrite increases in proportion in the coal seams towards the eastern part of the coalfield, and sclerotinite occurs in increased proportion in coal seams towards the western part. The reflectance in oil (Ro_max) varies from 0.50 to 0.58% in the coals of Rungta-Amlai, 0.46–0.56% in Kotma, and 0.53–1.05% in Bijuri subbasins. Chemically, the coals belong to type High Volatile Symbol B 4 of Class Bituminous. The significant trace elements are V (20–400 ppm); Cu, Ni, Co (up to 300 ppm); Mn, Ba, Sr, Zr (up to 800 ppm); and La (up to 1200 ppm). The trace elements show a tendency to increase in proportion towards the eastern part of the coalfield.To the immediate east of the coalfield lies the Chirimiri coalfield, of which the compositional characteristics are also presented. These data clearly suggest that the coals of the Son valley are different from those of the other Gondwana basins, i.e., Mahanadi, Godavari, and Damodar valley basins.