张家界下寒武统磷块岩中钛铀矿的晶出方式与成矿机理

Crystallization and Metallization of Brannerite in Marine Phosphorite of the lower Cambrian Niutitang Formation in Zhangjiajie Area,China

在张家界下寒武统牛蹄塘组底部海相磷块岩中首次发现了微晶钛铀矿,通过背散射电子图像、微区扫描电镜化学成分分析、元素面扫描和晶体结构分析等方法确定了钛铀矿的产出状态与晶出方式。作者认为同沉积期形成鲕粒状磷块岩并伴随海底热液喷流形成多种金属硫化物的混合物,海底热液喷流的持续,对同沉积期物质进行部分熔蚀、强熔蚀改造并发生重结晶作用,在动态环境下热液流体中多种元素处在过饱和状态出现铀多金属快速沉淀。下寒武统牛蹄塘组磷块岩中钛铀矿的发现和存在形式的确定为我国回收利用磷块岩型非常规铀资源提供了依据,也为海相磷块岩中铀多金属成矿作用与海底喷流沉积热液改造的成因联系提供了佐证。

Microcrystalline brannerite was discovered in marine phosphorite of the lower Cambrian Niutitang formation in Zhangjiajie Area, China,and the occurrence and crystallization of the brannerite were studied by using backscattered electron image, scanning electron microscope microanalysis, element surface scanning and crystal structure analysis. Results show that synsedimentary substances alteration, brannerite dissolution and recrystallization are strongly affected by sea bottom hydrothermally process.