甘肃天水地区百花岩浆杂岩的锆石LA-ICP-MSU-Pb定年及其地质意义  

Zircon LA-ICP-MS U-Pb Dating of the Gabbro from the Baihua Igneous Complex in Tianshui Area,Eastern Gansu,and Its Geological Significance

作　　者：裴先治[1] 刘战庆[1] 丁仨平 李佐臣[1] 李高阳[1] 李瑞保[1] 王飞[1] 李夫杰[1] 

机构地区：[1]西部地质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

出　　处：《地球科学进展》2007年第8期818-827,共10页Advances in Earth Science

基　　金：国家自然科学基金项目"扬子地块西北缘后龙门东段变质核杂岩形成机制和区域构造背景"(编号:40572121);国家自然科学基金重点项目"西秦岭-松潘构造结形成演化与大陆动力学研究"(编号:40234041);教育部科学技术研究重点项目"西秦岭北部造山带结构以及祁连-秦岭造山带构造关系"(编号:104175);中国地质调查局地质调查项目"甘肃省天水市幅1:250000区域地质调查"(编号:200013000154)共同资助

摘　　要：利用阴极发光和LA-ICP-MS微区定年分析方法,对甘肃天水地区百花岩浆杂岩中的辉长岩进行了单颗粒锆石U-Pb同位素分析。百花岩浆杂岩体主要由辉石岩—辉长(闪长)岩—闪长岩—石英闪长岩组成,构成较完整的同源岩浆演化序列,地球化学研究表明其形成于岛弧构造环境。对百花岩浆杂岩中辉长岩的LA-ICP-MS锆石U-Pb同位素定年结果表明,其同位素年龄为(449.7±3.1)Ma(MSWD=1.9),形成于晚奥陶世,表明西秦岭北带岛弧型岩浆岩的形成时代为晚奥陶世,结合区域地质资料,揭示出以西秦岭北缘关子镇蛇绿岩为代表的古洋盆的俯冲作用及产生岛弧型岩浆活动的时限为中晚奥陶世。Using cathodoluminescence（CL） imaging and LA-ICP-MS in site U-Pb isotope dating technigne, this paper presents zircon U-Pb dating for the gabbro from the Baihua igneous complex in Tianshui area, eastern Gansu pvovince and reveals interesting tectonic implication. Baihua igneous complex consists mainly of pyroxenite- gabbro （dioriie）-diorite-quartz diorite. They form a complete comagmatic evolutionary series. The tectonics environment discrimination of trace element geochemistry reveals the igneous complexs formed in an island-arc setting. The LA-ICP-MS single-zircons U-Pb age of the gabbro from Baihua igneous complex is （449.7 ±3.1 ） Ma （ MSWD = 1.9） ,which shows that the forming time of the island-arc type magmatite in northern zone of West Qinling is Late Ordovician,also reveals that the timing of subduction of paleo-ocean basin represented by the Guanzizhen ophiolite and resulting island-arc-type magmatic activities is probably Middle-Late Ordovician.

关 键 词：岩浆杂岩 辉长岩 LA—ICP—MS 锆石U-PB定年 天水地区 

分 类 号：P588[天文地球—岩石学] P597[天文地球—地质学]