应用电子探针研究蒙其古尔铀矿床含矿砂岩岩石学特征及铀矿物分布规律

Study on Petrological Characteristics and Distribution of Uranium Minerals of Sandstones in the Mengqiuer Uranium Deposit by Electron Microprobe,Xinjiang

应用精准的砂岩碎屑成分定量分析,可以为源区及沉积盆地分析等相关性质提供重要依据。本文在野外观察描述砂岩宏观特征的前提下,利用显微镜结合电子探针分析手段,对新疆蒙其古尔铀矿床中的含矿砂岩进行研究,探讨含矿砂岩岩石学特征及其中铀矿物的分布规律。结果表明:研究区含矿砂岩成分成熟度指数介于0.56~1.08,平均指数为0.78,即成分成熟度和结构成熟度低,成岩作用强烈;物源为一套混合型再旋回造山带区向过渡再旋回造山带区,最后向岩屑再旋回造山带区过渡的演变过程。碎屑物源主要来源于盆地南缘蚀源区石炭—二叠系中酸性火山岩,以及盆地周边那拉提山北缘、科古琴山、博努科努山南缘分布的一系列晚泥盆—早石炭世大哈拉军山组火山岩和少量古生代花岗岩。铀矿物类型主要为沥青铀矿、铀石及钛铀矿,其次发现有少量吸附态铀;背散射图像显示铀矿物的分布与炭屑、黄铁矿、金红石等密切共生。

Quantitative analysis of sandstone clastic composition can provide important basis for provenance and sedimentary basin investigation. Based on the observation and description of sandstone macroscopic characteristics in the field,the ore-bearing sandstones from the Mengqiuer uranium deposit in Xinjiang were studied by optical Microscope and Electron Microprobe. Petrological characteristics of sandstone and occurrences of uranium minerals are discussed. Results show that the compositional maturity index of the sandstone is 0. 56 - 1. 08 with an average index of 0. 78 , indicating low compositional maturity and low structural maturity. The source rock is derived from a mixed recycled orogenic belt transition to the orogenic belt, and finally to the evolution of lithic and orogenic belttransition. The source rocks originated mainly from the Carboniferous-Permian intermediate acid volcanics in the southern margin of the basin and the northern margin of the Nalati, Keguqin, and Bonukenu mountains, as well as the late Devonian-early Carboniferous Dahalajunshan volcanic rocks and Paleozoic granites. Uranium minerals are mainly pitchblende, coffinite, and brannerite with minor adsorbed uranium. The back-scattering image shows thatthe distribution of uranium minerals is closely related to charcoal, pyrite and rutile.