祁连造山带中段雾宿山群的构造属性探讨  

Tectonic affinity of the Wusushan Group in the central segment of the Qilian orogen

作　　者：丁仨平 裴先治[1] 李佐臣[1] 刘少锋[2] 李瑞保[1] 李高阳[1] 刘战庆[1] 

机构地区：[1]西部矿产资源与地质工程教育部重点实验室,长安大学地球科学与资源学院,陕西西安710054 [2]中国地质大学地球科学与资源学院,北京100083

出　　处：《中国地质》2008年第4期577-589,共13页Geology in China

基　　金：国家自然科学基金项目(40572121、40234041);教育部科学技术研究重点项目(104175)资助

摘　　要：通过对雾宿山群岩石组合特征和火山岩地球化学特征的分析,结合与周边区域地质背景的对比研究,探讨兰州西南一带雾宿山群的形成环境、构造属性及构造意义。雾宿山群主要为一套形成于中晚奥陶世的以中性、中基性火山岩及英安岩为主夹少量火山碎屑岩和正常沉积岩的岩石组合,经受低绿片岩相变质。火山岩不同岩类的地球化学特征均显示其形成于岛弧或弧前构造环境。综合分析雾宿山群岩石组合特征和火山岩地球化学特征并结合与西侧拉脊山构造带及北祁连造山带的对比,初步认为雾宿山群可能不是拉脊山构造带的东延,而是北祁连南缘岛弧带在兰州西南一带延伸的构造残块。雾宿山群构造属性的厘定,对祁连造山带的东延问题、祁连与秦岭造山带的交接关系及祁连造山带中东段构造格局的建立都具有十分重要的意义。Based on an analysis of the characteristics of the rock association and geochemistry of volcanic rocks of the Wusushan Group, combined with a comparative study of the regional geological setting of the neighboring regions, the authors discuss the environment and tectonic affinity and implications of the Wusushan Group in the southwest of Lanzhou in the Qilian orogen. The Wusushan Group is a rock association consisting mainly of intermediate and intermediate-basic volcanic rocks and dacite with small amounts of pyroclastic rocks and ordinary sedimentary rocks, which formed in the Mid-Late Ordovician and underwent low greenschist facies metamorphism. Geochemical characteristics of different types of volcanic rocks show that the rocks formed in an island arc or forearc tectonic setting. By analyzing the characteristics of the rock association and geochemistry of volcanic rocks of the Wusushan Group and comparing these characteristics with those of the Lajishan tectonic belt and North Qilian orogen, it is preliminarily thought that the Wusushan Group is probably not the eastward extension of the Lajishan tectonic belt but the structural remnants of the extension of the island arc belt at the southern margin of the North Qilian Mountains southwest of Lanzhou. The redefinition of the tectonic affinity of the Wusushan Group is of great significance for solving the eastward extension of the Qilian orogen, understanding the intersection relation between the Qilian orogen and Qinling orogen and establishing the tectonic framework of the east-central segment of the Qilian orogen.

关 键 词：祁连造山带 雾宿山群 岛弧火山岩 地球化学 

分 类 号：P583[天文地球—岩石学] P59[天文地球—地质学]