大兴安岭地区加格达奇东部早白垩世火山岩地层的厘定及地质意义

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

摘要: 大兴安岭地区加格达奇东部发育一套安山质凝灰角砾熔岩、安山质晶屑岩屑凝灰岩、安山岩，1：20万加格达奇幅区调将其划分为中晚侏罗世壮志组（J₂-3z）和二叠纪星火组（P₂x）.本研究在加格达奇东部大黑山地区和额尔格奇地区安山岩中获得锆石LA-ICP-MS U-Pb谐和年龄分别为120±2.1 Ma和123.1±2.3 Ma，结合岩石组合特征，将原上述划分厘定为下白垩统龙江组（K₁l），为大杨树盆地北部火山岩地层提供了新的同位素定年资料.

Abstract: 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.