前言山西东南部垣曲一带,广泛分布一套中元古界火山岩系—西洋河群。岩性以安山岩、玄武安山岩为主,夹有少量的正常沉积岩(砂页岩)。由老到新分为三个组:许山组、鸡蛋坪组和马家河组。厚度可达5200米。其中某些层位为枕状熔岩。其分布概况和采样位置如图1所示。全岩Rb-Sr等时 Preface In the area of ​​Yuanqu, southeast of Shanxi, there is a widespread distribution of a set of Middle Proterozoic volcanic rocks - the Western Yang River Group. The lithology is mainly andesite and basaltic andesite with a small amount of normal sedimentary rocks (sand shale). From old to new divided into three groups: Xu Shan group, egg Ping group and the Ma River group. Thickness of up to 5200 meters. Some of these beds are pillow lava. Its distribution and sampling location shown in Figure 1. Whole rock Rb-Sr isochronism