基于便携式色度、X荧光及高光谱的砂岩铀成矿环境研究——以鄂尔多斯盆地西北部特拉敖包铀矿产地为例

选取经济高效、轻便无损的分析技术是当前砂岩型铀矿绿色勘查和研究的现实需求。本文基于便携式色度、X荧光（XRF）、高光谱的光谱学技术，全面表征了鄂尔多斯盆地西北部特拉敖包铀矿产地环河组红杂色含矿建造的地质地球化学特征；构建了不同颜色砂岩的定量标准色度区间，查明了红色砂岩具有赤红色强氧化、褐（紫）红色较强的差异后生氧化作用；过渡带褐灰色和灰绿色砂岩普遍具有一定的弱氧化性，红度a的曲线发生多次渐变过渡，矿带内部存在多个氧化还原的地球化学界面，形成了多段的铀-钼-钒-铌等变价元素的共伴生富集。以上信息指示了研究区氧化还原作用的主成矿机制；绿色还原砂岩的红度值最小，是后期碱性还原流体渗出改造的产物。流体活动导致环河组地层发育绿泥石化、铁的还原-迁出、局部碳酸盐化等蚀变。该研究为沉积盆地不同地球化学性质含铀建造多尺度的铀成矿环境快速评价提供了案例及重要参考。

Metallogenic environment of sandstone-hosted uranium deposit based on portable colorimeter, X-ray spectrofluorometer and hyperspectrometer: Taking the Telaaobao uranium deposit in western Ordos Basin as an example

The selection of economical, efficient, lightweight and non-destructive analysis techniques is a practical requirement for the green exploration and research of sandstone-type uranium deposits. By the means of portable colorimeter, X-ray fluorescence (XRF) and hyperspectrum, this work comprehensively investigated the geological and geochemical characteristics of the red-variegated strata of the Huanhe Formation in the Telaaobao deposit, northwest of the Ordos Basin. The quantitative chromaticity interval standard was constructed to characterize the different colors of sandstone. It was found that the red sandstone underwent differential oxidation that included stronger original oxidation with a crimson and the relatively extensive epigenetic oxidation with brown (or purple) red color. The taupe gray and gray-green sandstones in the transition zone, were usually characteristic with a slight weak oxidation. The redness (a) curves of the sandstones displayed several gradual transition boundaries, indicating that some redox geochemical interfaces were located within the interior of the ore belt. As a result multiple coassociated enrichment of some variable valence elements includes uranium-molybdenum-vanadium-niobium. The above evidence suggests that redox was the main uranium mineralization mechanism in the study area. The green reduced sandstones owned the lowest value of redness, and they were transformed by the late alkaline and reducing fluids before uranium mineralization. Fluid activity event also resulted in the chloritization, ferric-iron reduction, local carbonation and other alterations of the Huanhe Formation. This study provides a case and important reference for the rapid and multi-scale evaluation on the metallogenic environment of uranium-bearing formations with different geochemical properties in sedimentary basins.