甘肃天水地区早古生代黄门川花岗闪长岩体LA-ICP-MS锆石U-Pb定年及构造意义  

LA-ICP-MS zircon U-Pb dating of Early Paleozoic Huangmenchuan granodiorite in Tianshui area of Gansu Province and its tectonic significance

作　　者：魏方辉[1] 裴先治[1,2] 李瑞保[1] 李佐臣[1,2] 裴磊[3] 高景民[1] 王银川[1] 刘成军[1] 吴树宽[1] 陈有炘[1] 

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [3]中国地质大学(北京),北京100083

出　　处：《地质通报》2012年第9期1496-1509,共14页Geological Bulletin of China

基　　金：国家自然科学基金项目<西秦岭北缘变形构造解析及其祁连-秦岭构造交接关系研究>(批准号:40972136);中央高校基本科研业务费专项资金项目<中央造山系(中西段)关键构造部位复合造山作用研究>(编号:CHD2011TD020);中国地质调查局地质调查项目<天水市幅1:25万区域地质调查(修测)>(编号:200013000154)

摘　　要：甘肃天水地区黄门川花岗闪长岩体位于北祁连造山带东端,侵位于晚奥陶世陈家河群中酸性火山岩系中,岩石学和地球化学特征表明其具有壳幔岩浆混合的特点。对黄门川花岗闪长岩体进行了LA-ICP-MS锆石U-Pb定年,结果表明该花岗闪长岩体的年龄为440.5Ma±4.4Ma,形成于早志留世。地球化学特征表明,黄门川花岗闪长岩体属于中钾钙碱性系列,具I型花岗岩的特征。构造环境判别表明其形成于安第斯型大陆边缘弧。综合区域地质背景,认为祁连造山带东端在早古生代期间发育有有限洋盆,洋盆向北俯冲消减产生大量弧岩浆岩。对进一步研究祁连与秦岭造山带构造交接部位早古生代的构造格局、演化等大陆动力学问题具有重要意义。Located in the northern Qilian orogenic belt of Tianshui region within Gansu Province,the Huangmenchuan granodiorite intruded into basic volcanic rocks of the Upper Ordovician Chenjiahe Group.The petrologic and geochemical characteristics show that this granodiorite was formed by emplacement of crust-mantle mixed type of magma.The results of LA-ICP-MS zircon U-Pb data of the granodiorite from Huangmenchuan show that the Huangmenchuan granodiorite was emplaced at 440.5Ma±4.4Ma,belonging to Lower Silurian.The element geochemical characteristics indicate that Huangmenchuan granodiorite belongs to middle-K cal-alkaline series with features of I-type granite.The granodiorite samples are located in Andeans-type continental margin granite area in the environment discrimination diagram.Based on regional geology,the authors hold that there existed a limited ocean basin in Early Paleozoic,and large quantities of arc-type magmatic rocks were produced by the northward subduction of the ocean crust in eastern Qilian orogenic belt.The study of the continental dynamics of the tectonic framework and the evolution history in the area between Qilian and Qinling orogenic belts is of great significance.

关 键 词：花岗闪长岩 LA-ICP-MS锆石U-PB测年 大陆边缘弧 北祁连造山带 天水地区 

分 类 号：P588.121[天文地球—岩石学] P534.4[天文地球—地质学]