扬子地台西缘震旦系-下寒武统黑色页岩中磷块岩环境地球化学分析

Environmental Geochemical Approach to Phosphorite in the Sinian—Lower Cambrian Black Shale in Western Yangtze Platform,China

本文分析了扬子地台西缘黑色页岩中磷块岩的主、微量元素地球化学特征,以及磷块岩中重金属的分布和赋存特征,探讨了富镉磷块岩的元素组成及其环境效应。结果表明,扬子地台西缘磷块岩富含P_(2)O_(5)、CaO等化学成因组分,而亏损SiO_(2),TiO_(2),Al_(2)O_(3),Fe_(2)O_(3),K_(2)O,Na_(2)O等碎屑组分。根据重金属富集特征,这些磷块岩可分为高富镉磷块岩和低富镉磷块岩,湘西和黔东北磷块岩属于高富镉磷块岩。高富镉磷块岩明显富集Cd、Mo、U、Ni、V、Co、Pb等重金属,为环境重金属污染源。磷块岩中Cd等重金属赋存于黄铁矿等硫化物矿物中,故在磷肥加工过程中去除黄铁矿等硫化物矿物,是预防磷肥施用导致的重金属污染的重要措施。

This paper analyzes geochemical characteristics of major and trace elements of phosphorite in black shale on the western margin of the Yangtze platform,as well as the distribution and occurrence of heavy metals in the phosphorite,and discusses the element composition of the cadmium-rich phosphorite and its environmental effects.The results show that the phosphorite in western Yangtze platform is enriched with chemical components such as P_(2)O_(5) and CaO,but depleted SiO_(2),TiO_(2),Al_(2)O_(3),Fe_(2)O_(3),K_(2)O,Na_(2)O.The characteristics of heavy metal enrichment show that the phosphorites in the area can be divided into the codmium highly enriched phosphorites and the cadmium slightly enriched phosphorites,and the phosphorites in western Hunan and northeastern Guizhou are the codmium highly enriched phosphorites.The codmium highly enriched phosphorites is obviously enriched in heavy metals such as Cd,Mo,U,Ni,V,Co,Pb,and is a source of environmental heavy metal pollution.Cadmium and other heavy metals in phosphorite was found to be hosted mainly within sulfide minerals.Therefore,the removal of sulfide minerals such as pyrite during the processing of phosphate fertilizer is an important measure to prevent heavy metal pollution caused by phosphate fertilizer application.