大兴安岭北部下侏罗统战备村组的建立及其地质意义

大兴安岭北部战备村地区出露一套火山岩,岩石组合主要为一套浅灰色、灰白色流纹质火山碎屑岩、流纹质火山熔岩、碎屑熔岩夹少量火山沉凝灰岩。在1∶5万区域地质填图的基础上,查明该套地层下部呈角度不整合覆盖于晚三叠世二长花岗岩之上,上部被中—上侏罗统塔木兰沟组平行不整合覆盖,锆石U-Pb同位素年龄为178~192Ma,时代为早侏罗世。根据《中国地层指南》关于新建"组"的要求,指定战备村剖面为层型,新建为战备村组。下侏罗统地层单位的建立,对大兴安岭早中生代火山构造岩浆活动的研究及中生代火山岩地层划分对比具有重要地质意义。

The establishment of the Lower Juras-sic Zhanbeicun Formation in northern Da Hinggan Mountains and its geological significance

The Zhanbeicun area in northern Da Hinggan Mountains develops a suite of volcanic rocks. The rock assemblages of the Zhanbeicun Formation are mainly a suite of light gray-gray rhyolitic pyroclastic rocks, rhyolitic lava, clastic lava with a small amount of volcanic tuff. On the basis of 1:50000 regional geological mapping, the authors found that the lower part of the formation covers Late Triassic monzonitic granite by angular unconformity, and the upper part of the formation is covered by Middle-Later Jurassic Tamulangou Formation by parallel unconformity. The zircon U-Pb isotopic age of Zhanbeicun Formation is about 178~192Ma, sug-gesting Early Jurassic. According to the rule of "formation" establishment in Stratigraphic Guide of China, the Zhanbeicun Formation is chosen as stratotype and established as Zhanbeicun Formation. The establishment of the Lower Jurassic stratigraphic unit has impor-tant geological significance for the study of early Mesozoic volcanic-tectonic magmatic activity in Da Hinggan Mountains and strati-graphic classification and correlation of Mesozoic volcanic rocks.