Rare earth elements and its development potential in the Longtan Formation coal of the Guxu mining area, South Sichuan coalfield

Objective Rare earth elements (REEs) are recognized as effective geochemical indicators and possess significant potential for industrial utilization. The Guxu mining area, a major coal−producing base in Sichuan Province, holds substantial research value in terms of elucidating the provenance of coal−bearing strata and reflecting sedimentary environments through REE studies.

Methods Seven coal samples from the C13, C14, C16, C17, C23, C24, and C25 coal seams of the Upper Permian Longtan Formation were collected. Inductively Coupled Plasma Mass Spectrometry (ICP−MS) was employed to determine REE concentrations. Geochemical parameters of REEs were applied to analyze the geochemical characteristics of the coal from the Longtan Formation.

Results The enrichment coefficients of REEs and their economic evaluation diagram revealed that the total REE content in the coal of the Longtan Formation ranges from 485×10⁻⁶ to 1629×10⁻⁶ (average: 863×10⁻⁶), classified as an enrichment grade. The C23, C24, and C25 coal seams fall within the prospective range for exploitation.

Conclusions The standardized REE distribution patterns and geochemical parameters (δCe, δEu, Y_N/Ho_N) indicate that the sedimentary provenance of the Longtan Formation coal−bearing strata was primarily derived from the weathering crust of the Mount Emei basalt in the Kangdian Oldland. The ∑REY–(La/Yb)_N discriminant diagram and negative Eu anomaly suggest that the peat swamp was also influenced by inputs of acidic rock debris. During marine−terrestrial transitional processes, clastic materials from the Mount Emei basalt weathering crust underwent further weathering, while seawater interactions promoted REE enrichment. The input of volcanic ash has led to the positive yttrium anomaly in the coal measures of the Longtan Formation in the Guxu mining area and contributed to the enrichment of rare earth elements.