Geochemistry of Late Triassic coals from the Changhebian mine in Chongqing, China

Five Late Triassic coal samples collected from Changhebian mine,Chongqing were characterized through a petrographic and geochemical investigation.The results showed that Pb is enrich in every samples,the mean content is 29.58 μg/g.Other hazardous elements such as Be(5.9 μg/g),Cr(28.6 μg/g),Cu(34.06 μg/g),As(10.03 μg/g) and Th(12.49 μg/g) are also concentrated in the coalfield.In addition,the content of REE ranging from 59.79 to 287 μg/g, with an arithmetic mean of 136.92 μg/g,which is closed to the Chinese coals(119.7 μg/g) and higher than that of American coals(53.59 μg/g).Especially, unusual character of REE in No.8 coal seam probably may be caused by the leaching process of ground water.The origin of the hazardous elements was mainly dominated by the source rock from Kangdian uplift.