摘要
分布于白云鄂博以东的碱性正长岩是华北地台北缘印支期富碱侵入岩北带的西延部分。这些碱性正长岩仅含微量碱性暗色矿物,以稀土元素含量高、具明显的负铕异常、轻重稀土强烈分馏,以及较低的Sr、Nb、Y及Ba含量而与阴山地区(包括北带和南带)的碱性正长岩有明显区别,它们可能为低压(<1.5GPa)条件下玄武质岩浆分异产物。大量的研究显示华北地台北缘中段包括阴山在印支期均已卷入造山运动中,从碱性正长岩带的分布、侵位机制及与造山花岗岩共存分析,该碱性正长岩应形成于造山后的伸展阶段。
Alkali syenites in northeast of Bayan Obo area are the western extension of the north belt of Indosinian alkaliˉrich intrsions in the north margin the of North China platform. But there are some differences between the rocks in this region and those in others. Alkali syenites in this region only contain microˉalkaliˉdarkˉcolored minerals. They are rich in REE, and have remarkable negative Eu anomaly, and deplete in Sr, Nb, Y and Ba relatively. They may be the result of basaltic magma fractional crystallization under 1.5 GPa. Many studies show that middle part of north margin along the North China platform including Yinshan moutain was involved in the orogeny during Indochina epoch. From the analysis of the distribution, emplacement mechanism and coexistence with orogenic granites, alkali syenites might emplace at the extensional stage of postˉorogeny.
出处
《地质调查与研究》
2004年第1期43-47,共5页
Geological Survey and Research
基金
中国地质调查局国土资源大调查项目(20001300008051)
关键词
内蒙古
白云鄂博
碱性正长岩
造山后伸展阶段
Bayan Obo
Inner Mongolia, alkali syenite, extensional stage
postˉorogeny
