DETERMINATION OF THE EARLY CRETACEOUS VOLCANIC STRATA IN EASTERN JAGDAQI, DAXINGANLING MOUNTAINS: Geological Implication

A suite of andesitic tuff breccia lava, andesitic crystal-lithic tuff and andesite is developed in eastern Jagdaqi, Daxinganling region, which was divided into the Middle-Late Jurassic Zhuangzhi Formation (J_2-3z) and Permian Xinghuo Formation (P₂x) by the 1:200 000 scale regional geological survey. The authors obtain the LA-ICP-MS zircon U-Pb ages of 120±2.1 and 123.1±2.3 Ma respectively from the andesites of Daheishan and Eergeqi areas. Combined with the characteristics of rock association, the original division above is redefined as the Lower Cretaceous Longjiang Formation (K₁l), which also provides new isotopic data for the volcanic strata in northern Dayangshu Basin.