酒泉盆地砂岩型铀成矿规律及白垩系找矿方向

Metallogenic Pattern of Sandstone-type Uranium and Prospecting Direction of Cretaceous in Jiuquan Basin

通过对典型砂岩型铀矿床(点)的综合对比,分析了铀矿地质特征,总结了酒泉盆地白垩系砂岩型铀矿成矿规律,明确了白垩系红层找矿标志。酒泉盆地下白垩统新民堡群为主要找矿目标层,其中花海盆地主攻目标层位为下沟组,酒西盆地主要目标层位为赤金堡组,酒东盆地为下沟组和中沟组。扇三角洲平原和扇三角洲前缘相为下白垩统新民堡群有利的沉积相带。酒泉盆地砂岩型铀矿主要控矿因素有构造、层位及岩性-岩相、后生氧化改造和铀源;铀成矿具有近铀源成矿、铀矿化大多发育在富铀花岗岩体周缘的富含炭屑的灰色砂体中、铀矿体主要发育在棕红色砂泥岩和灰色砂岩的过渡带中、铀成矿类型以沉积成岩为主叠加潜水氧化等规律。通过综合分析认为,相对稳定且适度抬升的构造斜坡带、长期隆升的富铀花岗岩体周缘、红色建造和灰色建造的过渡带、有利的容矿砂体及炭屑密集区或油气叠置区和多期次氧化作用叠加部位可作为酒泉盆地白垩系红层找矿方向。

Based on the comprehensive comparative analysis of typical sandstone type uranium deposits and occurrences,the geological characteristics of uranium metallization were analyzed,the metallogenic pattern of Cretaceous sandstone type uranium deposits in Jiuquan basin was summarized,and the prospecting criteria of Cretaceous red beds were clarified.Xinminpu Group of Lower Cretaceous is the main prospecting target layer in Jiuquan basin.Xiagou Formation is the main target layer of Huahai basin,Chijinbao formation is the main target layer of Jiuxi basin,and Xiagou Formation and Zhonggou Formation are the main target layers of Jiudong basin.Fan delta plain and front facies are favorable sedimentary facies belts in Lower Cretaceous Xinminpu Group.The main ore controlling factors of sandstone type uranium deposits in Jiuquan Basin include structure,strata,lithology and lithofacies,epigenetic oxidation transformation and uranium source.The sandstone type uranium deposit or occurrences in Jiuquan basin is near uranium source of the uranium rich granite body.Uranium ore bodies are mainly developed in the transition zone of brown red sand mudstone and gray sandstone,most of which are enriched in the gray sand body rich in carbon chips.The uranium mineralization type is mainly sedimentary diagenesis superimposed with phreatic oxidation.The relatively stable and moderately uplifted structural slope zone,the periphery of long-term uplifted uranium rich granite body,the transition zone between red formation and gray formation,the favorable ore bearing sand body,the area with dense carbon chips or oil-gas superimposed area,and the superimposed position of multi-stage oxidation can be used as the prospecting indicators of Cretaceous red beds in Northwest China.