甘肃北山红柳园地区泥盆系三个井组和墩墩山群 LA-ICP-MS锆石U-Pb测年及其意义

对甘肃北山红柳园地区三个井组下部玄武岩和墩墩山群安山质火山岩进行了LA-ICP-MS锆石U-Pb年龄测定,三个井组火山岩形成于420Ma±15Ma,相当于晚志留世;墩墩山群火山岩形成于367Ma±10Ma,相当于晚泥盆世。测年结果表明,晚志留世北山古生代洋盆已经俯冲消亡,并开始碰撞造山,而晚泥盆世墩墩山群火山岩则是北山早古生代洋盆碰撞造山后裂谷拉伸作用的产物,标志北山及相邻地区晚泥盆世进入到新的构造演化阶段 ——晚古生代板内伸展阶段。

LA-ICP-MS zircon U-Pb dating of Devonian Sangejing Formation and Dundunshan Group in Hongliuyuan, Beishan area, Gansu Province

Based on a study of LA-ICP-MS zircon U-Pb dating of basic volcanic rocks from lower Sangejing Formation and andesitic volcanic rocks from middle Dundunshan Group in Hongliuyuan of Beishan area, Gansu Province, this paper reveals that volcano-sedimentary rocks of Sangejing Formation were formed at 420 ± 15Ma, corresponding to Late Silurian, and volcanic rocks of Dundunshan Group were formed at 367 ± 9.5Ma, equivalent to Late Devonian. These data indicate that Beishan ocean basin was at the stage of the subduction-disappearance in Late Silurian, and entered into the collisional orogeny period, whereas the Dundunshan volcanic rocks were produced by rift extension and entered into a new phase, i.e., Late Paleozoic intraplate extension.