大兴安岭北部中生代火山岩特征及岩浆演化

Characteristics of Mesozoic volcanic rocks and magma evolution in northern Daxinganling

据火山岩岩石组合、地球化学特征、喷发旋回特征及岩浆来源,将大兴安岭北部中生代火山岩划分为三个岩浆演化旋回。晚侏罗世塔木兰沟—吉祥峰旋回火山岩为碱性系列亚碱性系列,岩浆来源于上地幔并有陆壳物质的混染;早白垩世的上库力旋回火山岩为高钾钙碱性系列,岩浆来源于地壳的部分熔融;早白垩世伊列克得旋回火山岩为碱性到亚碱性过渡系列,岩浆来自于地幔并受地壳的混染。综合研究表明,大兴安岭北部中生代火山岩形成于板内环境,早白垩世火山岩可能形成于大陆裂谷环境。

According to the rock assemblage, geochemistry, volcanic eruption cycle characteristics and magma origin, the Mesozoic volcanic rocks in northern Daxinganling area can be divided into three magma evolution cycles. Volcanic rocks of Tamulangou-Jixiangfeng cycle in Late Jurassic are alkaline-subalkaline series, and they derived from upper-mantle and were contaminated by continental crust materials. Volcanic rocks of the Shangkuli cycle in early Cretaceous are high in potassium calc-alkaline series. The magma came from partial melting of earth crust. Volcanic rocks of the Yilikede cycle in Early Cretaceous are alkaline-subalkaline transition series, which also derived from mantle contaminated by earth crust. It suggests that Mesozoic volcanic rocks in the studied area formed in a continental intraplate setting, but the early Cretaceous volcanic rocks probably formed in a continental rift.