浙江龙泉地区变质基性岩年代学、地球化学特征及构造意义  

Geochronological and geochemical characteristics of the metamorphic basic rocks and their tectonic implications in the Longquan area,Zhejiang Province

作　　者：刘远栋 刘风龙 张建芳 李翔 徐磊 温旭斌 倪伟伟 LIU Yuandong;LIU Fenglong;ZHANG Jianfang;LI Xiang;XU Lei;WEN Xubin;NI Weiwei(Zhejiang Institute of Geological Survey,Huangzhou,311203;Zhejiang Province Industrial EP Design&Research Institute Co.Ltd,Hangzhou,311203)

机构地区：[1]浙江省地质调查院,杭州311203 [2]浙江省工业环保设计研究院有限公司,杭州311203

出　　处：《地质学报》2021年第2期413-426,共14页Acta Geologica Sinica

基　　金：浙江省基础性公益性战略性地质工作项目(编号[省资]2018007、[省资]2018006);中国地质调查局项目(编号12120114043101)资助成果。

摘　　要：浙西南龙泉地区集中出露一套中深变质岩系,是华夏地块的重要组成部分,对其形成时代和成岩构造属性等问题历来存在争议。本文通过对龙泉变质岩中变质基性岩的地球化学研究,认为这些岩石的原岩成岩环境至少有两类:Ⅰ类岩石稀土配分曲线、微量元素蛛网图特征均显示与IAB的相似性,微量元素比值和图解判别均指示这套岩石形成于与俯冲有关的岛弧构造环境;Ⅱ类岩石稀土配分曲线和微量元素蛛网图均与OIB有相似性,微量元素比值和图解判别也指示这套岩石形成于与俯冲无关的OIB构造环境。多种不同构造属性的岩石共生,佐证了原龙泉岩群变质岩系为一形成于早古生代的俯冲增生杂岩。变质基性岩锆石U-Pb测年获得其峰期变质时间为404~402Ma。龙泉俯冲增生杂岩的厘定对重新认识丽水-余姚断裂带构造属性、区域构造格架的建立以及进一步分析华夏造山系物质组成与结构提供了新资料。The formation age,diagenetic,and tectonic attributes of a set of medium-deep metamorphic rock series exposed in the Longquan area,southwestern Zhejiang Province,an important component of the Cathaysian massif,remains controversial.Based on petrogeochemical studies of the metabasites from the Longqun metamorphic rocks,the diagenetic tectonic environments of these rocks can be divided into at least two types.TypeⅠrocks have the same REE distribution curves and spider diagram of trace element with IAB.The trace element ratio and discrimination diagrams indicate that these rocks were formed in an island arc setting which was related to subduction.TypeⅡrocks have the same REE distribution curves and spider diagram of trace element with OIB.The trace element ratio and discrimination diagrams indicate that these rocks were formed in a within-plate tectonic environment which were not relevant to the subduction.The rocks symbiosis of different tectonic attributes proves that the original Longquan Group is a subduction accretion complex.The zircon U-Pb dating of metabasites yielded the peak metamorphic ages between 404~402 Ma.This provides new data for reevaluatingthe tectonic attributes of the Lishui-Yuyao fault zone,the establishment of the regional tectonic framework,and the further analysis of the material composition and structure of the Cathaysian orogenic system.

关 键 词：变质基性岩 地球化学 俯冲增生杂岩 早古生代 龙泉 

分 类 号：P548[天文地球—构造地质学] P588.3[天文地球—地质学]