Mineralogical and Geochemical Characteristics of Lithium and Rare Earth Elements in High-Sulfur Coal from the Donggou Mine, Chongqing, Southwestern China

Abstract

Coal and coal by-products are considered as the potential raw materials for critical elements (e.g., rare earth elements, Li, Ga, Ge, etc.), which have attracted much attention in recent years. The purpose of this study is to investigate the mineralogical and geochemical characteristics, and controlling geological factors of lithium and rare earth elements in the Lopingian (Wujiaping Formation) coal from the Donggou Mine, southeastern Chongqing Coalfield, China. Results indicate that lithium and rare earth elements are significantly enriched in the Donggou coals, which could be new potential alternative sources for critical elements. Concentrations of lithium and rare earth elements in the Donggou coals gradually increase from top to bottom. Lithium is mainly associated with kaolinite, while rhabdophane, florencite, goyazite, and xenotime are the main hosts of rare earth elements. The controlling geological factor is the groundwater leaching of underlying tuff, and to a lesser extent, the terrigenous clastic materials input from the top layer of the Kangdian Upland. This study provides mineralization information for lithium and rare earth elements exploration in coal measures.

Mineralogical and Geochemical Compositions of Ammonian Illite-Enriched High-Rank Coals of the Xingying Mine, Northeastern Chongqing, China

“…The subhedral and colloidal anatase and fracture-filling apatite also suggest a hydrothermal origin. Rhabdophane, a secondary mineral containing REY, is rare in coal but is not uncommon in late Permian coals from southwestern China and considered as a product in relation to the hydrothermal origin. , Rhabdophane was confirmed in the roof, coal, and floor samples and occured in the granular form in the matrix of NH 4 -illite (Figure A–F), indicating a hydrothermal origin.…”

“… 62 If the UCC-normalized Eu anomaly occurs positive or negative in coals, it is suggested that the inorganic materials derived from mafic or felsic compositions, respectively. 62 The Eu anomaly has been used in the Huayingshan, 71 Nantong, 50 and southeastern Chongqing Coalfields 34 for indicative of the sediment source region being not the mafic basalts of the Kangdian Upland. The REY distribution patterns indicate that the inorganic material of the Xingying coals is from the mafic basalts of the Kangdian Upland, owing to the significant positive Eu anomalies, which further confirmed the results mentioned above.…”

“…Five representative samples were analyzed for modes of occurrence of minerals using scanning electron microscopy in conjunction with energy-dispersive spectrometry (SEM-EDS). The SEM-EDS analysis procedure and conditions were also reported by Zou et al 34 …”

“…Then, the coal low-temperature ashes (LTAs) and roof, parting, and floor samples were subjected to mineral composition analysis. The analysis condition of XRD was reported in detail in previous studies. , Based on the XRD diffractograms, the minerals were quantitatively determined using the Siroquant technique. Five representative samples were analyzed for modes of occurrence of minerals using scanning electron microscopy in conjunction with energy-dispersive spectrometry (SEM-EDS).…”

Environmental Technologies to Treat Rare Earth Element Pollution: Principles and Engineering

“…This would offer the potential to reduce our dependence on other countries for these critical materials and also create new industries in regions where coal has played an important economic role. Zou et al (2020) carried out a detailed study to understand the controlling geological factors for the enrichment of not only REE but also another demanding element, Li, in coal from the Donggou Mine (southeastern Chongqing Coalfield, China). The possible recovery of REE from abundant coal and coal ash is an exciting new research area, representing a dramatic paradigm shift for coal, innovations to REE manufacturing and bypass mining.…”