沽源—多伦盆地火山岩类和花岗岩类同位素地质年代学及铀成矿条件研究

本文对沽源-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至世产物，其形成年龄为125—135Ma。指出本区花岗岩浆活动有前海西期、海西期、印支期和燕山期，不存在文献中提到的自北而南分布的3条东西向海酉期花岗岩浆活动带。本文还指出该区区域铀成矿作用具有多期次的特点，同一矿床铀成矿作用的叠加是形成富铀矿体的前提。该区火山岩类钠含量较低，对铀成矿不利。然而，在不利的地质背景中局部存在利于铀成矿的地段和岩性，应作为今后重点的找矿对象。

RESEARCH ON U-METALLOGENIC CONDITIONS AND ISOTOPIC GEOCHRONOLOGY OF VOLCANIC ROCKS AND GRANITOID IN GUYUAN-DUOLUN BASIN

On the basis of systematic research on U-metallogenic conditions and isotopicgeochronology of volcanic rocks and granitoid in Guyuan-Duolun basin, the authors proposethat volcanic rocks of Zhangjiakou and Huaqiying Formations in the basin were formed inEarly Cretaceous epoch with the age of 125-135Ma, indicating that there were granitic magma activities during Pre-Hercynian, Hercynian, Indosinian and Yanshanian ages, and threeHercynian EW-trending granitic magma belts distributed from north to south, reported inliteratures do not exist in the basin.It is concluded that the regional U-mineralization possesses multiphase and multi-stagecharacteristics, a prerequisite to the formation of rich uranium ore bodies in a deposit is thesuperimposition of U-mineralizations, the volcanic rocks in the area are not favorable for Umetallogenesis because of their lower uranium abundance, but there are locally favorable Umineralized zones and rocks in un favorable geologic artting, which must be the targets for Uprospecting in basin.