赛什腾山一带火山岩LA-ICP-MS锆石U-Pb年龄及其地球化学特征

摘要

赛什腾火山岩广泛分布于柴北缘构造带的赛什腾山一带,为一套中基性火山熔岩,主要岩石类型有玄武岩、安山玄武岩、玄武安山岩及安山岩.前人将该套火山岩划归为寒武一奥陶纪滩间山群,但缺乏同位素测年数据及古生物化石依据,笔者对赛什腾火山岩中玄武安山岩进行了LA-ICP-MS锆石U-Pb测年,获得(256.9±0.7) Ma的测年数据,时代为晚二叠世,与滩间山群的形成时代明显不同,说明赛什腾火山岩与区域上滩间山群火山岩为不同时期岩浆喷发活动形成的产物.地球化学特征显示赛什腾火山岩具有岛弧火山岩的构造属性.%The Saishiteng volcanic rocks,as a group of intermediate basic volcanic lava,are widely distributed in the Saishiteng Mountain area of structural belt of north margin of Caidam basin.The mainly rock types include basalt,andesite-basalt,basaltic andesite and andesite.The previous set the volcanic rocks into the Cambrian-Ordovician Tanjianshan Group.However,the lack of isotopic dating data and fossil as a basis for the times.So the author made LA-ICP-MS zircon U-Pb dating for the basaltic andesite of the S aishiteng volcanic rocks and obtained data of (256.9±0.7) Ma.The times is Late Permian,obviously different from the formation time of the Tanjianshan Group,which shows that the Saishiteng volcanic rocks and the volcanic rocks of the Tanjianshan Group in the region are the products of magmatic eruption in different periods.The geochemical characteristics show that the Saishiteng volcanic rocks have the tectonic settings of island arc volcanic rocks.