内蒙古阿巴嘎旗地区新生代玄武岩基本特征及成因

General characteristics and origin of Cenozoic basalt from Abagaqi region, Inner Mongolia

内蒙古阿巴嘎旗及其以北地区新生代玄武岩是更新世中心式火山活动产生的大陆溢流玄武岩,该区玄武岩以高碱、富钛、贫铝为特征,属于钠质碱性玄武岩系列。源区是软流圈上地幔,玄武岩是部分熔融和分离结晶两种作用的结果。地幔橄榄岩部分熔融产生玄武质岩浆,部分原始地幔岩浆未经变异沿构造通道直接喷出地表形成碧玄岩、碱性橄榄玄武岩;部分原始地幔岩浆在上升过程中因停顿,原始地幔岩浆发生橄榄石分离结晶作用,部分橄榄石从岩浆中析出,最终岩浆喷出地表形成橄榄拉斑玄武岩。研究该区新生代玄武岩基本特征,探讨岩浆起源和岩石产生的构造环境对认识该区岩石圈地幔和软流圈性质具有重要意义。

The Cenozoic basalt from Abagaqi region ,Inner Mongolia are continental flood basalt, produced by center-type volcanism in the Pleistocene.The basalts is characterized by Al(2)O(3)=11.5%～(13.0%, )Na(2)O>K(2)O and TiO(2)>2.3%,chemically belong to the soda-alkaline series and were derived from asthenospheric source region. Two processes of partial melting and fractional crystallization would be responsible for the generation of the basalts. The basaltic magma was generated by partial melting of peridotites in the mantle. Basanite and alkali-olivine basalt was formed by partial primary magma along structural thoroughfare direct ejected. Partial primary magma ascended into a chamber within the continental crust, where it could cease moving up further and was fractionated to some extent,some of olivine was fractionated from the magma. Followed the magma along structural thoroughfare ejection formed olivine tholeiite.Features,origin and structure setting of the Cenozoic basalt from Abagaqi region, Inner Mongolia is important for understanding lithospheric mantle and asthenosphere nature.