西宁盆地北缘白垩系砂岩型铀矿成矿条件及找矿前景分析

Ore-forming Conditions and Prospecting Potential of Cretaceous Sandstonetype Uranium Deposits in the North Margin of Xining Basin

文章通过对西宁盆地北缘包马庄-五峰镇一带的构造演化特征、蚀源区铀源条件、含矿目的层特征、水文地质条件、后生蚀变特征、铀矿化特征及白垩系沉积建造特征进行系统分析,结合研究区钻孔连井剖面等资料,综合探讨了西宁盆地北缘砂岩型铀成矿环境及条件,认为盆缘的富铀花岗岩体为沉积盆地提供了丰富的铀源,中生代后期构造反转形成的剥蚀天窗为含铀含氧水的渗入、渗出提供了通道。盆地北缘斜坡带包马庄-五峰镇一带辫状河三角洲前缘水下分支河道微相发育部位是该区砂岩型铀矿找矿的重点方向,下白垩统河口群为主要找矿目标层位,找矿类型以层间氧化带型为主,次为潜水氧化带型。研究区各种成矿要素匹配良好,具备形成中型以上的砂岩型铀成矿潜力。

Based on the systematic analysis of the tectonic evolution,uranium source,ore target layers,hydrogeological conditions,epigenetic alteration,uranium mineralization and Cretaceous sedimentary formation,the metallogenic environment and conditions of sandstone type uranium deposit in the northern margin of Xining Basin were comprehensively discussed with the data of borehole and the borehole section.The uranium-rich granite in the margin of the basin was believed to have provided abundant uranium source for the sedimentary basin,and the denudation window formed by structure inversion in the Late Mesozoic provided a channel for the infiltration of uranium-bearing oxygen-water.The distribution area of subaqueous branch channel of braided river delta front in Baomazhuang-Wufengzheng of the northern slope of the basin is the main orientation for the exploration of sandstonetype uranium deposit,and the Lower Cretaceous Hekou Group is the main target layer.The main prospecting type should be the interlayer oxidation zone type,followed by phreatic oxidation type.Because the metallogenic factors in the study area are matched well,therefor the study area is of the potential to form middle size sandstone-type uranium deposit.