黔北凤冈地区碳酸盐型铀矿成矿物质来源研究

Study on the Sources of Carbonate-Type Uranium Mineralization in Fenggang Area,Northern Guizhou

为了探究黔北凤冈地区碳酸盐型铀矿化的物质来源,文章对黔北凤冈地区的沙坪铀矿点高品位矿石中的方解石开展LA-ICP-MS微量元素研究。研究表明:沙坪铀矿点受近南北向杨家堡断裂控制,赋存于娄山关组和桐梓组白云岩中,成矿过程分为方解石(Cal-1)-石英-沥青铀矿-黄铁矿(Py-1)阶段和方解石(Cal-2)-石英-萤石-有机质-黄铁矿(Py-2)阶段;LA-ICP-MS分析结果显示两阶段方解石中稀土元素在球粒陨石标准化配分模式图上具有明显的左倾特征,Y/Ho值集中于23.37~45.79和31.47~45.87。这些地球化学特征与围岩和下伏牛蹄塘组富铀泥岩相似,因此推测围岩娄山关组白云岩和桐梓组白云岩以及下伏牛蹄塘组富铀泥岩共同为沙坪铀矿点提供了成矿物质。

In order to explore the source of carbonate-type uranium mineralization,this paper studied the trace elements of calcite by La-ICP-MS in the Shaping high-grade uranium ore occurrence in Fenggang area of northern Guizhou.The results showed that the Shaping U-ore occurrence was endowed in dolomite of the Tongzi Formation and the Loushanguan Formation and controlled by the Yangjiabao fault in the north-south direction,the mineralization process was divided into calcite(Cal-1)-quartzpitchblende-pyrite(Py-1)phase and calcite(Cal-2)-quartz-fluorite-organic matter-pyrite(Py-2)phase.The results of La-ICP-MS analysis showed that the chondrite normalized REE pattern of Cal-1 and Cal-2 had obvious left-leaning characteristics,and the Y/Ho ratios were concentrated in 23.37~45.79 and 31.47~45.87,respectively.These geochemical features are similar to the surrounding rocks and the uranium-rich mud of the Niutitang Formation,so it is speculated that the dolomite of the Tongzi Formation and the Loushanguan Formation,and the uranium-rich mud of the Niutitang Formation together provided the uranium source for the Shaping occurrence.