Pb—Isotopic Characterization of Major Indian Gondwana Coalfields: Implications for Environmental Fingerprinting and Gondwana Reconstruction

An extensive database of the isotopic composition as well as content of lead (Pb) has been created in this study from Indian Gondwana coal deposits. Indian Gondwana coal are mostly bituminous to sub–bituminous and occurs as seams inter-banded with sediments. They typically have high ash content (35–50%), which makes them a potential heavy pollutant, considering that very large quantity of coal is burnt for thermal power plants, smelters etc. 110 from different seams spread over the major Indian Gondwana coalfields, that are primarily used for power generation in thermal power plants and fly ash from respective five thermal power plants, have been analysed for their isotopic composition as well as the content of Pb. The results indicate variability of coals from Gondwana basins of India in terms of their concentration and Pb—isotopic ratios. The Pb isotopic composition of Indian Gondwana coals range 0.7150–0.8845 for ²⁰⁷Pb/²⁰⁶ Pb and 1.9484–2.2231 for ²⁰⁸Pb/²⁰⁶ Pb with Pb concentration within 3.2–566 mg kg⁻¹. The variability of the Pb—content and its isotopic composition can be attributed to high and variable ash—content of the coal seams including its pyrite content as well as more radiogenic behaviour. However, within a seam Pb—isotopic ratios vary within a narrow range. Similarly the Pb isotopic composition obtained in the fly ash analyses range 0.8478–0.8757 for ²⁰⁷Pb/²⁰⁶ Pb and 2.1070–2.1706 for ²⁰⁸Pb/²⁰⁶Pb. These values have an increasing trend with respect to the feed coal Pb isotopic compositions when compared to the respective coal—deposits. The inventory generated in terms of Pb isotopic composition and content in Indian Gondwana coals would contribute to establish a background for identifying relative contribution of coal, especially those used in coal-based thermal plants for the Pb pollution in India. Not only this, the unique Pb isotopic composition of coals from south Indian Gondwana coalfields can be compared to the coal deposits of Amrey Group of Antarctica to offer a good constrain to achieve a tighter fit between India and Antarctica in a Gondwana framework and hence can have a wider implication for Gondwana reconstruction, once data set from Amrey Group becomes available.