俄罗斯远东陆内高镁安山岩的发现及其地质意义

Discovery of intracontinental high-Mg andesites in Russian Far East and its geological implication

在俄罗斯远东分布大面积的新生代玄武质岩石,主要岩石类型包括玄武安山岩和玄武质粗面安山岩。该火山岩的SiO 2=55.42%~57.34%,Al 2O 3=14.61%~15.01%,MgO=4.92%~5.78%,Fe 2O 3=8.58%~8.89%,Mg^#[=100 Mg/(Mg+Fe^2+)]=53.1~56.3,CaO=5.82%~6.62%,(Na 2O+K 2O)=5.15%~6.45%,属亚碱性系列,并具有高镁安山岩的地球化学属性。结合前人的定年结果(17.1~20.6 Ma)和所产出的构造位置,可以将其定义为新生代陆内高镁安山岩。岩相学与岩石化学揭示这些高镁安山岩没有经历明显的岩浆演化过程,化学组成接近原始岩浆。俄罗斯远东地区出露的新生代高镁安山岩,是新生代陆内岩浆作用的重要组成部分。

Cenozoic basaltic rocks are widely distributed in Russian Far East,including basaltic andesites and basaltic trachytic andesites.These volcanic rocks are characterized by SiO 2=55.42%~57.34%,Al 2O 3=14.61%~15.01%,MgO=4.92%~5.78%,Fe 2O 3=8.58%~8.89%,Mg^#[=100 Mg/(Mg+Fe^2+)]=53.1~56.3,CaO=5.82%~6.62%,and(Na 2O+K 2O)=5.15%~6.45%,belonging to subalkaline series and have an affinity to high-Mg andesites.Based on the previous dating results of 17.1~20.6 Ma and the tectonic location occurred,they can be defined as Cenozoic intraplate high-Mg andesites.Their petrography and petrochemistry reveal that these high-Mg andesites did not experience obvious magmatic evolution process and their chemical compositions are similar to primary magma.The Cenozoic high-Mg andesites occurred in Russian Far East are important components of the Cenozoic intraplate magmatism.