二连盆地脑木更地区黏土矿物特征及其与铀成矿关系研究

The characteristics of clay mineral and its relationship to uranium mineralization in Naomugeng Area,Erlian Basin

本文对二连盆地脑木更地区赛汉组矿层及围岩进行XRD黏土矿物成分分析,以探讨黏土矿物特征与铀成矿作用之间的关系。经电子探针成分分析,该区铀矿物为沥青铀矿,见黄铁矿与沥青铀矿共生。采用X射线粉晶衍射、扫描电镜、电子探针等分析手段,测定黏土矿物相对含量、微观形貌特征,结果显示研究区黏土矿物主要为蒙脱石、高岭石、伊利石,蒙脱石含量在三者中最高,其与高岭石含量呈较明显的负相关性,表明其主要由高岭石转化而来,偏碱性的孔隙流体造成黏土矿物的蚀变和转换。矿层及围岩中黏土矿物的种类及含量差异性不明显,表明黏土矿物与铀成矿及富集作用相关性不明显,在赛汉组砂岩型铀矿成矿过程中黏土矿物可以吸附铀,但不是铀成矿及富集的最主要因素。通过对赛汉组砂岩中黏土矿物含量及特征研究,该区存在两期流体作用,一期是高岭石反映的偏酸性环境,另一期是蒙脱石反映的碱性环境,揭示了由酸性→碱性流体的作用过程。黏土矿物可以作为铀成矿过程中后生流体示踪的重要标志。

In order to explore the relationship between the characteristics of clay minerals and uranium mineralization,XRD analysis of clay minerals in Saihan Formation and surrounding rocks in Naomugeng area,Erlian Basin was carried out.Electron probe analysis shows that the main uranium mineral in this area is pitchblende,finding the coexistence between pyrite and pitchblende.The relative contents and micro-morphologies of clay minerals were determined and observed by using X-ray powder diffraction、SEM and electron probe analysis.The result shows that the clay minerals in sandstones in the study area are mainly montmorillonite,kaolinite and illite.The content of montmorillonite is the highest among the three,there is a negative correlation between the content of montmorillonite and kaolinite,it is mainly transformed from kaolinite,Alkaline pore fluids caused altera⁃tion and transformation of clay minerals.There is no significant difference in the types and contents of clay minerals in the ore layer and surrounding rock,indicating that the correlation between clay minerals and uranium mineraliza⁃tion and enrichment is not significant.,clay minerals can adsorb uranium during the mineralization process of sandstone type uranium deposits in the Saihan Formation,but it is not the most important factor for uranium enrich⁃ment.By studying the content and characteristics of clay minerals in the sandstone of the Saihan Formation.There are two phases of fluid interaction in this area,the first phase is a slightly acidic environment of kaolinite,another phase is the alkaline environment of montmorillonite,revealed the process of action from acidic to alkaline fluids.Clay minerals can serve as important indicators for tracing epigenetic fluids in uranium mineralization processes.