青海柴达木盆地东部巴依地区铀成矿环境及矿化特征分析

Analysis of Uranium Metallogenic Environment and Mineralization Characteristics in Bayi Area,Eastern Qaidam Basin,Qinghai

文章以柴达木盆地东部巴依地区新近系油砂山组为主要研究对象,通过铀矿地质调查、实测剖面、物化探测量、岩矿鉴定及元素地球化学分析等方法,研究分析了区内的铀矿化特征和成矿环境,研究表明:柴达木盆地东部巴依地区油砂山组为一套辫状河三角洲前缘沉积,发育“泥-砂-泥”结构,含砂率较高,砂质岩层占总地层厚度约53.6%,单层砂体厚度最大为20 m,一般为3~5 m,砂体较为疏松,埋深浅,一般为200~400 m;油砂山期为富氧的古沉积环境,整体为淡水相,气候以干热环境为主导,在上、下油砂山分界期附近存在干湿转变气候,提供了利于后期铀成矿作用的古沉积环境;区内铀矿化发育,在油砂山组中新发现2条铀异常带,铀异常产于黄褐色含炭砂(砾)岩中,见钒钾铀矿,是砂岩型铀矿化产物。综合分析认为巴依地区铀成矿地质条件好,其中上下油砂山组可作为柴达木盆地东部铀矿勘查的主要找矿目的层。

This article focuses on Youshashan Formation in Bayi area of the eastern Qaidam Basin,and analyzes the uranium mineralization characteristics and ore-forming environment in the area through methods such as uranium geological survey,measured profiles,physical and chemical exploration,rock and mineral identification,and elemental geochemical analysis.The results show that Youshashan Formation is a set of braid river delta front deposits in Bayi area of the eastern Qaidam Basin,with a“mud-sand-mud”structure with a high sand percentage,and the sandy layer account for about 53.6%of the total formation thickness.The thickness of the single-layer sand body is up to 20 m,generally 3~5 m,the sand body is relatively loose,and the buried depth is generally 200~400 m.Youshashan Formation was deposited in freshwater with an oxygen-rich paleosedimentary environment.The climate was mainly dry and hot,and there was a dry to wet transition while the deposition of the upper and lower Youshashan,which was conducive to the late uranium mineralization.Uranium mineralization was developed in the area,and two new uranium anomaly zones have been found in Youshashan Formation.Uranium anomaly occurred in yellow-brown carbonaceous sand(gravel)rock as vanadium-potassium-uranium ore,which is believed to be the product of sandstone type uranium mineralization.The comprehensive analysis shows that Bayi area has good geological conditions for uranium mineralization and can be regarded as a new area for uranium exploration in the eastern Qaidam Basin.Youshashan Formation is believed the target layer and expected to get breakthrough in the exploration of sandstone uranium deposit.