内蒙古敖汉旗朝吐沟组的地质时代

GEOCHRONOLOGY OF THE CHAOTUGOU FORMATION IN AOHAN QI,INNER MONGOLIA

对采自大兴安岭南部朝吐沟组建组剖面的酸性火山岩(流纹岩)样品开展锆石U-Pb LA-ICP-MS年代学分析,测试结果显示:样品具有岩浆成因的特征,加权平均年龄为374±10 Ma,指示该酸性火山岩形成于晚泥盆世,发育该套火山岩的朝吐沟组为晚泥盆世地层.研究认为沿华北板块北缘展布的朝吐沟组火山-沉积建造形成于晚泥盆世一个次稳定—非稳定的被动陆缘盆地沉积环境,这对更准确地认识大兴安岭乃至整个东北地区泥盆纪—石炭纪构造演化以及古地理格局具有重要意义.

The paper analyzes the zircon U-Pb LA-ICP-MS geochronology of the acid volcanic rock(rhyolite)samples from Chaotugou Formation type section in southern Daxinganling Mountains.The test results show that the samples are of magmatic origin with the weighted mean age of 374±10 Ma,indicating the acid volcanic rock was formed in Late Devonian,and thus the Chaotugou Formation developed in the volcanic rock belongs to Late Devonian.It is concluded that the volcanic-sedimentary formation of Chaotugou Formation along the northern margin of North China Plate was formed in a substable-unstable passive continental margin basin sedimentary environment in Late Devonian,which is of great significance for more accurate understanding of the Devonian-Carboniferous tectonic evolution and paleogeographic pattern in Daxinganling Mountains and even Northeast China.