中国西南地区二叠纪乐平世陆生生物大灭绝期煤中砷和硒的演化及古环境意义

为了探讨中国西南地区二叠系乐平统(上二叠统)龙潭组中下部煤系不同煤组分中砷、硒的含量和演化及古环境意义，对近10年来采集于中国西南扬子地台的二叠系乐平统龙潭组主采煤层的原煤、亮煤、煤矸石、黄铁矿结核等样品中砷、硒元素含量进行了测定和分析，并与中国华北地台一些煤矿的上石炭统-下二叠统太原组、山西组的原煤、镜煤、亮煤、煤矸石、黄铁矿结核等样品中砷、硒含量进行对比分析。结果表明：西南地区乐平统龙潭组煤的砷、硒含量变化较大，但总体高于华北晚石炭世和早二叠世煤的砷、硒含量；西南二叠系乐平统龙潭组大多数的亮煤中砷、硒含量高于原煤全煤样(刻槽样)中的砷、硒含量，也远远高于同煤层煤矸石的含量，龙潭组部分亮煤的砷含量尤其高，为55～338 mg/kg，还发现砷含量为89 mg/kg的亮煤。但华北上石炭统-下二叠统的镜煤中的砷、硒含量与之相反，低于原煤全煤样的砷、硒含量，其中砷含量非常低，为063～129 mg/kg。说明西南地区上二叠统煤中的砷和硒与煤的有机质密切相关，可能主要来源于成煤古植物。在西南乐平世早、中期第Ⅰ幕陆生生物集群灭绝事件期间，陆生动物的食物--植物中有毒有害元素砷、硒含量明显增加，陆生环境或泥炭沼泽中可溶性砷、硒含量增加。

Evolution of arsenic and selenium of coals during mass extinction of land species in the Permian in southwestern China and its palaeoenvironmental significance

To investigate the arsenic(As)and selenium(Se)content and evolution in different coal components of the coal measures of the Longtan Formation as well as its palaeoenvironmental significance during the early and middle periods of Late Permian(Lopingian)in southwestern China，the As and Se content were detected and analyzed  in the samples of raw coal，clarain，coal gangue and pyritic nodule which were collected from the main coal seams in southwestern China during the last 10 years，and the results were compared with that of the Taiyuan Formation and Shanxi Formation of Late Carboniferous and Early Permian in the North China Plate. The results show that the As and Se content of the  coal measures of Longtan Formation in the Late Permian in southwestern China changed greatly and the As and Se content is higher than that of the Late Carboniferous and Early Permian coals in the North China Plate；the As and Se content of the Late Permian clarain coals in southwestern China is higher than that of the channel sampling coals or raw coal and coal gangue，especially the As content of the Late Permian clarain(from 55 to 338 mg/kg，some reaches 89 mg/kg)is much higher in southwestern China. The As and Se content in the coals of Taiyuan Formation and Shanxi Formation of the Late Carboniferous and Early Permian in the North China Plate is contrary to southwestern China，that is, the As and Se content of the Late Carboniferous and Early Permian vitrain and clarain is very low. The As content ranges from 063 to 129 mg/kg，lower than that of the channel sampling coals or raw coal and the gangue in the North China Plate. The analysis indicates that the source of As and Se in the Late Permian coals in southwestern China is closely related with the organic component of coals，and the As and Se in coals is mainly derived from the coal forming paleoplants in southwestern China. The results also show that during the mass extinction of land species in the Late Permian，the land species food，namely, the plants had an increasing content of As and Se，and the content of the soluble As and Se in land environment or the peat
swamp also increased.