GEOCHRONOLOGY OF THE CHAOTUGOU FORMATION IN AOHAN QI, INNER MONGOLIA

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.