鄂尔多斯盆地纳岭沟铀矿床目的层岩石学及铀存在形式

Lithologic characteristics and modes of occurrence of uranium of the target strata in the Nalinggou uranium deposit of Ordos Basin

中侏罗统直罗组下段下亚段是纳岭沟铀矿床的主要含矿层位,该层段发育辫状河沉积体系,砂体连通性、渗透性好,富炭屑、黄铁矿等还原质,具有良好的铀成矿条件。本文通过显微镜下观察、X射线衍射分析、扫描电镜等分析测试手段,对纳岭沟铀矿床直罗组下段下亚段砂岩岩石学特征进行研究,观察含铀矿目的层砂岩中的蚀变现象及蚀变矿物特征,探究黏土矿物、黑云母等矿物的蚀变转化关系。通过α蚀刻径迹、电子探针实验等分析测试手段,对纳岭沟铀矿床铀矿物的成分类型和存在形式进行探究。探讨含铀矿层砂岩岩石学特征与铀矿物存在形式之间的关系,发现纳岭沟铀矿床铀的富集、赋存形式、成分类型与含矿砂岩中的矿物蚀变转化中的物质交换密切相关,纳岭沟铀矿床铀成矿是受古层间氧化带控制,叠加了后期热液流体改造作用的结果。

The lower part of the first member of Zhiluo Formation of Middle Jurassic is the main uranium ore-bearing layer of theNalinggou uranium deposit. Because of the formation has braided river sedimentary system features such as good sand body connectivity and permeability, rich reducing substances（charcoal and pyrite）, it has good conditions for uranium mineralization.Using multiple testing means such as microscope microscopy, X-ray diffraction analysis, scanning electron microscopy analysis, the authors studied sandstone rock characteristics. Alteration phenomena and altered mineral characteristics of the uranium target strata was observed. the conversion relationship in clay minerals, biotite and other minerals was explored. Component analysis was conducted, and existing forms of uranium mineral in the Nalinggou uranium deposit were investigated using α track etching,electron microprobe analysis and tensile test. By discussing the relationship between petrologic features and existing form of uranium minerals in the ore-hosting horizon, it is found that the enrichment of U, occurrence of U and component type of U were closely related to the exchange of material in the mineral alteration transformation, and uranium mineralization in Nalinggou area was controlled by paleo-interlamination oxidized zone and was affected by the later hydrothermal fluid.