Enrichment of V in Late Permian coals in Gemudi Mine, Western Guizhou, SW China

This paper reports on the petrological and geochemical compositions of K9 and K4 coals in the Late Permian Longtan Formation in the Gemudi Mine, which is located in the western Guizhou, southwest (SW) China. Critical metal concentrations have not been reported and there is a significant difference in the V concentration between the lower part and the upper part in the K9 coal of Gemudi Mine. Thus, it is a good research object of the enrichment mechanism of V. The studied coals are medium volatile bituminous coals that are characterized by a medium-high ash yield (21.7% and 37.7% on average, respectively) and a low sulfur content (0.81% and 0.18% on average, respectively). Vitrinite is the major maceral group in both coals, and collotelinite and collodetrinite contribute the most to it. Clay minerals (mainly kaolinite, illite, and illite/smectite mixed) are the majority of the minerals, quartz, carbonite minerals and pyrite are also found in the coal samples. Correspondingly, SiO2 and Al2O3 are the major components in ash, and both of them are highly correlated with the ash yield. Vanadium (213 mu g/g on average) is the single enriched element in K9 coal, and it is also enriched in K4 coal. Vanadium is significantly enriched in the lower part of K9 coal, but it is depleted in the upper portion. A correlation analysis indicated that V in K9 coal mainly has an organic association, and it is positively related to telinite. Whereas, the cell and crack filling chlorite is likely to be the predominant occurrence mineral of V. Terrigenous detritus from the Emeishan basalt in the Kangdian Upland represents main origin of V in Gemudi coals, and hydrothermal fluids reformed some part of V in the K9 coal. The reducing depositional environment provides the preservation conditions as well.