【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。更多还原

【Abstract】 Using cathodoluminescence(CL)imaging and LA-ICP-MS in site U-Pb isotope dating technigue,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(diorite)-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.更多还原