Mineralogical and Elemental Analysis of Some High-Sulfur Indian Paleogene Coals: A Statistical Approach

The northeast (NE) region of India has a prominent reserve of Oligocene to Eocene coals of significant interest. An extensive study on the mineralogical and elemental composition of nine high-sulfur coal samples from the various Paleogene coalfields of the NE portion of India was conducted to understand the modes of occurrence and distribution patterns of the minerals, as well as the trace and rare-earth elements (REEs) in these coals. The majority of minerals associated with the NE region coals mainly includes, kaolinite, illite, mixed-layer illite/smectite, zircon, pyrite, goyazite, chlorite, xenotime, siderite, titanium oxide (anatase or rutile), iron-bearing gahnite, rhabdophane, carbonate, and jarosite. The minerals are of different origins, such as authigenic, syngenetic, and epigenetic. The presence of ferropseudobrookite is observed for the first time in any Paleogene Indian coals. Calcite is dominant in the coals. The NE region coals are enriched in F (70.40 mu g/g), Pb (21.84 mu g/g), Sr (125.69 mu g/g), Zr (285.93 mu g/g), and Ba (117.80 mu g/g). However, NER coals contain lower REEs (on average), such as Ce (17.92 mu g/g), Eu (0.30 mu g/g), Y (8.51 mu g/g), La (30.82 mu g/g), Ce (65.61 mu g/g), and Nd (27.55 mu g/g), as well as Th (18.68 mu g/g). The high Zr and Sr contents in the NE Indian coals are attributed to the presence of zircon and goyazite in the coals. The statistical analysis of the major oxides, sulfur, and trace elements in the coals is also performed to know their corelations. Minerals from the aluminosilicate group are prominent in NE Indian coals.