Enrichment Characteristics and Genetic Analysis of Rare Earth Elements in the Lower Longtan Formation Coal of Qianbei Coalfield, Guizhou Province.

Rare earth elements and yttrium (REY) are enriched in the coal of the lower Longtan Formation, Late Permian, in western Guizhou Province. This study focuses on the No. 15 coal seam of the lower Longtan Formation in the Qianbei Coalfield, with coal samples collected from 14 coal mines. Inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence spectroscopy (XRF) were employed to determine the concentrations of REY and major elements in the coal, and to analyze the enrichment degree and genesis of REY in the study area. The results indicate that the REY content in the No. 15 coal seam of the Qianbei Coalfield ranges from 107.13 to 1953.18 ppm, with an average of 750.62 ppm, and enrichment is dominated by LREY. The primary material sources of this coal seam are intermediate-acid volcanic rocks and alkaline volcanic ash from the Emeishan Large Igneous Province (ELIP), which define the background of REY enrichment. The warm and humid paleoclimate promoted the weathering of source rocks. Additionally, the paleogeographic patterncharacterized by a west-high and east-low topographic configurationcoupled with flowing water bodies, provided the necessary transport dynamics for terrigenous debris. The transitional marine-continental sedimentary environment offered depositional sites for both terrigenous debris and volcanic ash. Following diagenesis, REY was preserved and further enriched in the coal.