Geological controls on the mineral matter and trace elements of coals from the Fuxin basin, Liaoning Province, northeast China

Abstract

This study summarizes the results of geological, petrographical, geochemical and mineralogical studies performed to determine the geological controls on coal quality of the Fuxin deposit, Liaoning Province, in northeast China. The study is focused on the Haizhou mine, which currently mines a coal-bearing clastic Lower Cretaceous series affected by a diabase intrusion. Three major coal seams are differentiated: the Taiping, the Middle and the Shunjawan. Fuxin coal is a high quality coal with low ash and sulphur contents (4.0 to 18.0% HTA and 0.3 to 0.8%S tot) and high calorific value (5600 to 7500 cal/g, as received basis). Coal impurities (both major and trace elements) are at very low concentrations; only a high Mn concentration (up to 8600 ppm) was detected. The rank of Fuxin coal (mainly high volatile B-bituminous coal) is clearly influenced by the diabase intrusion, which has induced the formation of natural coke from coal. Natural coke surrounds the diabase dykes and sills with a thickness ranging from a few centimetres up to 1.5 m. In addition, a wide aureole made up of high volatile A-bituminous coal formed around the coke. The diabase intrusion was not a major source of elemental mobilization, Mn being the only element clearly enriched in the coal (by 1 to 2 orders of magnitude). However, major changes in major and trace element distribution (affinities) were induced in the coal by the intrusion. The geochemical study revealed that these changes were the consequence of the mobilization of organic-, sulphide- and carbonate-associated elements.