Geochemistry of trace elements of Tertiary coals of India

Abstract

Forty-one coal samples from seven Tertiary basins of the Himalayas, representing coalfields of the States of Assam (sub-bituminous), Meghalaya (lignitous to sub-bituminous), and Jammu and Kashmir (low volatile bituminous to semi-anthracite) have been spectrographically analyzed. The trace elements analyzed were Ge, Ni, Co, Cu, Pb, Mo, Zr, Mn, Cr, Ba, Ga, V, Sr, B, Nb, Sn, La and Y. There are differences in trace element concentrations between the Eocene coals of northeastern and northwestern India. A significant difference also exists between the Eocene and Oligocene coals of northeastern India. The results show that some of the elements are significant for the identification and correlation of the coal seams. The element Cr can be used as a marker or index element for the Oligocene coals of the Makum and Dilli-Jeypore coalfields of northeastern India, and Mn for the Ecocene coals of Meghalaya of northeastern India. The interpretation of organic/inorganic association of the trace elements indicates that elements such as Ni, Co, Ba, V, Sr, Cr, Y, Ge and Nb are associated with the organic fractions. Pb and Cu show affinity with both the organic matter and sulphides. Mn shows affinity with the organic matter and mineral matter, while Ga is exclusively related to the mineral matter. Further, it has been revealed that the Eocene and Oligocene coals of northeastern India originated under marine conditions. In contrast, the Eocene coals of northwestern India give significant evidence of a high influx of fresh water during coal development and show parity with the fluviolacustrine coals of Lower Gondwana, so far as the concentrations of the trace elements are concerned.