Petro-chemical characterization and evolution of Vastan Lignite, Gujarat, India

The present paper entails the results of the chemical and petrological studies carried out on Vastan Lignites of Gujarat. Petrographically there is an unambiguous dominance of huminite group of macerals over the liptinite and inertinite groups and is chiefly represented by telohuminite and detrohuminite. Ulminite dominates among telohuminite while attrinite and densinite mainly contribute to detrohuminite. Liptinite and inertinite groups are recorded comparatively in small concentrations. Argillites are the main inorganic component while the carbonates and sulphides contribute meagerly to the total mineral matter content.Chemically these lignites are characterized by high moisture content with moderately high volatile matter and variable ash contents. The fixed carbon and the elemental carbon show a moderate concentration. The sulphur content is more in the Lower seam with an average content of 1.59%.The study reveals that these lignites originated under moderate to high water cover in limnic environments with evidences supporting anaerobic decay of the organic matter with a loss of structural components of vegetal matter to a lesser extent. Moreover, the influx of fresh waters raised the pH of the paleomire which was further raised by carbonate rich surface water and was responsible for high sulphur content in some of the sections.