大兴安岭北段克-河地区满克头鄂博组流纹岩的年代及地球化学特征

摘要

This paper is a study on the chronology and geochemistry of the rhyolites in Manketou'ebo Formation as a way to determine the Manketou'ebo Formation time and tectonic environment of Keyihe area in north-central Greater Xing'an Range.The study of chronology uses U-Pb method and the study of geochemistry, defined as the test of Major, rare and trace elements of rhyolites samples, can determine the tectonic setting by the data analysis.The study reveals that the Manketou'ebo rhyolites is classified as a high-K low-Al type in calc-alkaline series, ranging in age between 132.20±0.49 Ma,which is the early Cretaceous rather than late Jurassic, as previously thought;the formation of the rhyolites in Manketou'ebo Formation is probably closely associated with the lithosphere extension after the closure of Mongol-Okhotsk Ocean.%为了确定大兴安岭北段克-河地区的满克头鄂博组形成时代及其构造环境,对满克头鄂博组流纹岩开展年代学、岩石地球化学的研究.年代学研究采用U-Pb测年法,岩石地球化学研究是对流纹岩样品进行主量元素、微量元素及稀土元素测试,通过数据分析研究确定其构造背景.结果表明:满克头鄂博组流纹岩属钙碱性岩石系列中的高钾低铝质类型;年龄为132.20±0.49 Ma,形成于早白垩世,并不是以往认为的晚侏罗世;满克头鄂博组流纹岩的形成可能与蒙古-鄂霍次克洋闭合后的造山带伸展作用有关.