Geochemistry of two high-lithium content coal seams, Shanxi Province, China

Prospecting for trace and rare earth elements will only increase in the coming decades as the world expands into sustainable energy and the use of digital technology. A key component of finding these resources is understanding how they are distributed, mobilized and emplaced. The coal beds in Shanxi Province in China have already been identified as a resource with elevated trace elements, especially lithium. This study has extended the understanding of trace elements in the region from examination of two sites, one in the Ningwu coalfield (the No. 11 coal seam) and the other in the Qinshui Basin (the No. 8 coal seam). Lithium, in particular, but most trace elements, in general, were found to be associated with the inorganic fraction of the coal seams. Specifically, trace elements are highest in the sediments overlying the coal and in the interbedded partings. The coal beds themselves were also enriched, especially in Li, but their concentrations vary in direct proportion with ash yield. Differing degrees of maturation (the Ningwu site ~0.70% Ro; the Qinshui site ~2.50% Ro) seem to have little effect on the association of trace elements with inorganics. Using the relationship between Rb vs Y + Nb, the ultimate provenance of the sediment (and thus the trace elements) may be from the weathering products of regionally proximal granites. However, two high ash coal outliers, both from the Qinshui Basin sampling site, appear to have a different trace element source, as yet unidentified, compared to all other samples. The REY (rare earth elements and Y) patterns indicate hydrothermal fluids are also responsible for REY enrichments in the coal seams.