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对沽源-多伦盆地火山岩类和花岗岩类进行了同位素地质年代学、地球化学和铀成矿条件的系统研究。确定了该区张家口组、花吉营组火山岩类均属早白垩世产物,其形成年龄为125～135Ma。指出该区花岗岩浆活动有前海西期、海西期、印支期和燕山期,且查明不存在文献中提到的自北而南分布的三条东西向海西期花岗岩浆活动带。该区火山岩类为钙碱性和碱钙性,均来源于相同或相近成分物源不同程度的部分熔融,且未经历明显的岩浆分异作用。花岗岩类具有同熔型和改造型两类,前者来源于下地壳,后者来源于上地壳。还指出该区区域铀成矿作用具有多期次特点,同一矿床铀成矿作用的叠加是形成富铀矿体的前提。明确指出该区火山岩类铀含量较低,对铀成矿不利。然而,在不利的地质背景中也存在许多有利铀成矿的地段和岩性,应作为今后找矿的重点对象。
We systematically studied the isotopic geochronology, geochemistry and uranium metallogenic conditions of the volcanic rocks and granites in the Guyuan-Duolun Basin. It is confirmed that the volcanic rocks of Zhangjiakou Formation and Huajiying Formation belong to the Early Cretaceous in this area and their formation ages are 125 ~ 135Ma. It is pointed out that the granitic magmatism in the area includes the former Hercynian, Hercynian, Indosinian and Yanshanian periods, and the absence of the three east-west Hercynian granitic magmatism active belts from the north to south distribution mentioned in the literature. The volcanic rocks in this area are calc-alkaline and alkaline-calcareous, which all originated from different degrees of partial melting of the same or similar provenances, and have not undergone obvious magmatic differentiation. Granites have the same type of melting and remodeling, the former from the lower crust, the latter from the upper crust. It is also pointed out that the uranium metallogenesis in this area has multi-stage characteristics. The superposition of uranium mineralization in the same deposit is the prerequisite for the formation of uranium-rich ore bodies. It is clearly pointed out that the volcanic rocks in this area have lower uranium content and are detrimental to uranium mineralization. However, there are many favorable uranium metallogenic sites and lithologies in the unfavorable geological background, which should be the focus of prospecting in the future.