小兴安岭东北部金林岩体全岩-角闪石Rb-Sr年龄

中国东北地区小兴安岭北段分布的兴东群与佳木斯地区的麻山群一直被认为是早元古代形成的变质岩系。近年来麻山群500 Ma左右变质年龄的确定为兴东群的变质时代提出了疑问。研究表明，分布于小兴安岭北部金林林场的兴东群四子山组“混合岩”为一套片麻状石英二长岩-花岗岩侵入体，岩石全岩-矿物（角闪石）Rb-Sr等时线年龄为(482±19) Ma，这表明小兴安岭巨型花岗岩带中存在早古生代岩浆事件。兴东群变质作用可能也与早古生代构造-热事件有关。早古生代花岗岩的确认对该区地质构造演化研究具有重要意义。

Rb - Sr Isotopic Dating of the Jinlin Pluton by Whole Rock-Hornblende Method in the Northeast Xiao Hinggan Mountains

The Xingdong Group distributed in the northern Xiao Hinggan Mountains and the Mashan Group in the Jiamusi area, Northeast China, are always considered to be Early Proterozoic metamorphic rocks. However, the confirmation of approximate 500 Ma metamorphic age of the Mashan Group raised a question on the metamorphic age of the Xingdong Group. According to the research of the paper, the “migmatite” of the Sizishan Formation, Xingdong Group distributed in northern Xiao Hinggan Mountains should be a suit of gneissic quartz monzonite granite intrusions. Their whole rock mineral (hornblende) Rb-Sr isochronic dating is (482±19) Ma, indicating that an Caledonian magmatic events existed in the giant granitic belt of the Xiao Hinggan Mountains. The metamorphism of the Xingdong Group may also have relation to the Early Caledonian tectono thermal events. The identification of the Early Caledonian granites is of important significance in studying the geological tectonic evolution of the area.