Influences of Low‐Temperature Hydrothermal Fluids on the Re‐distributions and Occurrences of Associated Elements in Coal — A Case Study from the Late Permian Coals in the Zhijin Coalfield, Guizhou Province, Southern China

Abstract  The occurrences of associated elements and their genetic factors in the No. 30 coal seam in the Zhijin Coalfield were studied using instrumental neutron activation analysis, inductively coupled plasma-atomic emission spectroscopy, and a scanning electron microscope equipped with an energy-dispersive X-ray analyzer. And, a microscope photometer system (Leitz MPV-III) was used to observe the characteristics of coal petrology. According to the influence degree by the siliceous low-temperature hydrothermal fluids, the organic matter is divided into four types: A, B, C, and D of the hydrothermally-altered organic matter (HAOM). The study shows that the high content of Fe (2.31%) is not from pyrite, but mostly from the siliceous low-temperature hydrothermal fluids. The occurrences of the associated elements in the four organic matter types are different. The contents of Fe, Si, and Al are decreasing, but S and Cu are increasing in the order of the HAOM-A, HAOM-B, HAOM-C, and HAOM-D. The losing rate of sulfur in organic matter is 0.35% and the content of Fe taken from the low-temperature hydrothermal fluids into the organic matter is 0.794% during the siliceous low-temperature hydrothermal fluids invading the coal seam. The above facts indicate that the low-temperature hydrothermal fluids play a crucial role in the re-distributions and occurrences of associated elements in coal.