Lithium isotopic composition of two high‑lithium coals and their fractions with different lithium occurrence modes, Shanxi Province, China

Abstract

Coal and coal-bearing strata have been considered as potential economic sources of lithium, and, as such have attracted significant attention. Significantly high concentration of lithium has been found in the coals from Shanxi Province, North China. This study examined the lithium isotopic composition of two high-Li coals of different ranks (XJ-8 anthracite and DLT-11 bituminous coal) and their fractions (such as organic-, silicate-) obtained through sequential chemical extraction. Lithium was found to be predominantly associated with silicates. Lithium isotopic compositions in DLT-11 are more positive (δ7Li > 0‰) than those in XJ-8 coal (δ7Li < 0‰) irrespective of which are bulk coals or leachates. Specifically, the carbonate fraction in DLT-11 had the most positive lithium isotopic composition among all fractions. Carbonate fluid hosting positive lithium isotopic composition seems to have had an effect on the lithium isotopic composition of DLT-11 coal. Lithium isotopic composition of XJ-8 anthracite may be a result of lithium re-distribution between organic and inorganic components during coalification, and this was also responsible for lithium isotopic homogeneity in the coal seam.