ABSTRACT

South Africa is an important participant in the global coal market. The four Upper coal seam situated in Springs-Witbank Coalfield was subjected to XRT sorting and subsequent mineralogical studies to characterize REE content. The average total REE content (LREE and HREE) of the coal were 280 ppm on ash basis. The surrounding elemental composition besides carbon primarily consisted of O, Si, S and Fe with minor quantities of Al, P and Ti. Major minerals, such as quartz, dolomite, illite, gypsum, siderite, pyrite correlated positively with ash content (r > 0.9) except kaolinite, and microcline, indicating incongruent source and formation mechanisms. Additionally, the HREEs Lu, Tm, Dy, Ho, Gd and Tb displayed strong correlations (r > 0.95) with ash content but were negatively associated with fixed carbon. Sc is negatively associated with coal ash. Fixed carbon is weakly associated with La but negatively associated with HREEs. La showed a weak association with Ce. Y is strongly correlated with HREE elements especially with Dy, Tm, Lu and Ho while at the same time LREE are strongly associated with Ce, Pr, Nd, La, Eu but negatively with Sc and fixed carbon levels.

摘要

南非是全球煤炭市场的重要参与者。位于 Springs-Witbank 煤田的四个上部煤层经过 XRT 分选和随后的矿物学研究，以表征 REE 含量。煤的平均总 REE 含量（LREE 和 HREE）以灰分计为 280 ppm。除碳外，周围的元素组成主要由 O、Si、S 和 Fe 组成，还有少量的 Al、P 和 Ti。石英、白云石、伊利石、石膏、菱铁矿、黄铁矿等主要矿物除高岭石、微斜晶外与灰分含量呈正相关（r>0.9），来源及形成机制不一致。此外，高稀土元素 Lu、Tm、Dy、Ho、Gd 和 Tb 与灰分含量有很强的相关性（r > 0.95），但与固定碳呈负相关。Sc与煤灰呈负相关。固定碳与 La 弱相关，但与 HREE 负相关。La 显示出与 Ce 的弱关联。Y 与 HREE 元素密切相关，尤其是与 Dy、Tm、Lu 和 Ho 密切相关，同时 LREE 与 Ce、Pr、Nd、La、Eu 密切相关，但与 Sc 和固定碳含量呈负相关。