酒东盆地红山地区下白垩统新民堡群灰白色蚀变带特征及其与铀成矿的关系

Feature of Off-white Alteration Zone and Its Relation to Uranium Mineralization in Lower Cretaceous Xinminpu Group in Hongshan Area,Jiudong Basin

研究区位于酒东盆地东北缘红山地区。通过对下白垩统新民堡群后生氧化改造作用的研究,认为灰白色弱氧化、强水解蚀变带是层间氧化带的一部分。铁和有机质是沉积岩中常见的色素,当含氧水进入目的层砂体时,砂体中的有机质、低价铁(Fe2+)等化合物被氧化,导致岩石褪色;同时氧化作用导致砂岩中长石水解,形成以高岭石为主的白色黏土矿物,使岩石增白。增白与褪色的双重作用是砂岩总体上变白的重要原因,其所形成的灰白色蚀变岩位于强氧化的紫红色-黄色蚀变亚带与灰色原生岩石带之间的一定范围内。铀矿化(体)产在弱氧化、强水解灰白色砂岩与原生灰色砂岩界面附近偏灰色岩石一侧[1-2]。灰白色蚀变带与铀成矿关系密切,可作为区域性白垩系砂岩型铀矿的找矿标志之一。

The study area is located in Hongshan area,northeast of Jiudong basin.Base on the research of epigenetic alteration in the Lower Cretaceous Xinminpu group,it was believed that the strong hydrol-ysis and weak off white oxidation is the component of phreatic interlayer oxidation zone.Iron and organic matter are commonly occurred pigment in sedimentary rock,when groundwater containing oxygen infil-trated into the rock,they can oxidize and bleach the pigment in sandstone,mean while the hydrolysis of feldspar produce light color dominated clunch minerals such as Kaolinite.Whitening and depigmentation are the important reason of off white alteration in sandstone.The off white zone is located between strong oxidation mauve yellow sub zone and original gray zone.The off white zone is in close rela-tion with uranium mineralization and can be used as a sign for uranium exploration in Lower Cretaceous sandstone type uranium deposits in this area.