鄂尔多斯盆地西缘惠安堡地区铀成矿特点

Primary research on the uranium metallogenetic characteristics in Hui′anpu area of the western margin of Ordos basin

典型层间氧化带砂岩型铀矿产出于次造山带构造背景。惠安堡地区处于鄂尔多斯盆地西缘褶断带马家滩断褶带,传统理论认为这里不利于后生铀成矿作用的进行,但近几年的找矿实践证明该断褶带的铀成矿作用既有典型层间氧化带砂岩型铀矿的一些特点,也有自己的特殊性。该区的地层倾角较大,砂体厚度也较大;地下水近源、短途、双向径流,形成多个复杂的局部水动力系统;沿背斜东、西两翼发育的层间氧化带具有层数多、双向发育、期次多、氧化深度大、沿倾向延伸较短、纵横方向厚度变化快、连续性较差、地球化学分带不明显、水解蚀变作用弱等特点;铀矿化具有层数多、期次多、品位较低、厚度较小、矿化分散、深度较大、矿化主要受层间氧化带翼部控制、前锋成矿较弱、矿化纵横连续性差、矿后改造较强等特征。

The typical interlayer oxidation zone sandstone-type uranium deposit is produced in the sub-orogenic tectonic setting.Hui′anpu area is located at Majiatan fault-fold belt in the western margin of Ordos basin.According to traditional theory,this area is not favourable to the formation of epigenetic uranium mineralization,but recent years exploration have discovered some deposits in this area,uranium mineralization at the fault-fold belt not only has the characteristic of typical interlayer oxidation zone sandstone-type uranium deposits,but also has its own particularity.Here the strata dip angle is large and the thickness of sand body is relatively large.Groundwater in the strata is near the source and its runoff distance is short.The groundwater has also two-way runoff and form a number of complex local hydrodynamic systems.Interlayer oxidation zones had developed along the eastern and western wings of an anticline and bore the characteristics of multi stage,two-way development,multi-layers,great depth,short dipping extension,rapid thickness changes in vertical and horizontal directions,poor continuity,not sufficiently clear in the geochemical zonation,and weak in hydrolytic alteration.The uranium mineralization has characteristics of multi-stages,lower grade,smaller thickness,dispersed,multi layers,large depth,strong in wings,but weak in the front,poor continuity in vertical and horizontal directions and strong epigenetic alteration.