Petrographic and chemical characterizations of coals from Hongsa coal mine, Xayabouly province, Lao PDR

This study presents the details of petrographic and chemical characterizations of the Cenozoic coal from the Hongsa coal mine, Xayabouly Province, Lao PDR. Eighty-nine samples from a drill core consist mainly of lignite, carbonaceous clays, and clays. From the petrographic study, the Hongsa coals are dominated by huminite, followed by liptinite, and the very few funginite of the inertinite group. They show both features of humic and sapropelic coals. A moderate amount of mineral matters are silica and clay minerals. Based on maceral and mineral assemblages, they indicate a forest swamp environmental setting with a moderate amount of sediments supplied by low-energy water flow. Moreover, the characteristics of maceral preservation indicated the depositional environment was an anoxic condition with low oxidation. The limnotelmatic environment points to the deposition of peat between an open moor and a wet-forest moor environment. According to a chemical analysis, the coals are classified as lignite A and lignite B with high ash content and low sulfur.