新疆蒙其古尔砂岩型铀矿床含矿目的层中黄铁矿类型与铀成矿关系初析

黄铁矿是砂岩型铀矿床中常见的载铀矿物之一,可为成矿提供有利的还原环境。以新疆蒙其古尔砂岩型铀矿床含矿目的层中黄铁矿为研究对象,通过偏光显微镜观察与电子探针微区化学成分分析方法相结合进行研究。结果表明:区内含矿目的层中出露有三种不同形态的黄铁矿,即草莓状黄铁矿、立方体自形晶黄铁矿和不规则状黄铁矿,它们在结晶形态、赋存形式及化学成分方面均有所不同;其硫铁平均比值显示为S/Fe(草莓状)S/Fe(立方体自形晶)S/Fe(不规则状),化学成分总体呈现出富Mo、As、Co,贫Ni、Pb、Se、Zn、Ag、Sb。另外在铀成矿过程中,不规则状黄铁矿与铀矿物的分布存在密切关系,为成矿流体提供了必要的还原剂,继而为区内含矿目的层中铀的富集提供了有利条件。

The Study on Pyrite in Ore Target Layer of Mongqigur Sandstone-type Uranium Deposit, Xinjiang

Pyrite is one of the most common uranium-bearing minerals in sandstone-type uranium deposits, which can provide favorable reduction environment for mineralization. In this paper, the pyrite in the ore target layer of the Mongqigur sandstone-type uranium deposit in Xinjiang is taken as the research object, and polarization microscope and EPMA were used to study the chemical composition. The results show that there are three different forms of pyrite in the ore target layer, namely strawberry pyrite, cubic euhedral crystal pyrite and irregular pyrite, which are different in crystal morphology, occurrence form and chemical composition. The average ratio of sulphur to iron is S/Fe (strawberry pyrite) < S/Fe (cubic euhedral crystal pyrite) < S/Fe (irregular pyrite). The chemical composition is rich in Mo, As, Co and poor in Ni, Pb, Se, Zn, Ag and Sb. In addition, in the process of uranium mineralization, irregular pyrite is closely related to the distribution of uranium minerals, which provides the necessary reducing agent for ore-forming fluids, and then provides favorable conditions for uranium enrichment in ore target layer in the area.