内蒙古色日崩地区白音高老组流纹岩岩石地球化学特征及地质意义

GEOCHEMICAL CHARACTERISTICS AND GEOLOGICAL IMPLICATION OF THE RHYOLITE IN BAIYINGAOLAO FORMATION FROM SERIBENG, INNER MONGOLIA

摘要: 内蒙古西乌旗色日崩地区早白垩世白音高老组流纹岩为高硅（SiO₂=78.32%~86.80%）、富碱（K₂O+Na₂O=3.84%~7.63%）、高铝（Al₂O₃=8.59%~13.70%），低MgO、CaO、TiO₂、MnO，稀土元素与微量元素地球化学特征显示其类似于A型花岗岩特征；低Ti/Y、Nb/Y与Ti/Zr比值，高Rb/Nb与Rb/Y比值以及Sr、Eu强烈亏损，表明白音高老组流纹岩为上地壳物质部分熔融成因，形成于早白垩世非造山板内伸展环境.

Abstract: The rhyolite in Early Cretaceous Baiyingaolao Formation from Seribeng of Xiwuqi, Inner Mongolia is characterized by high SiO₂(78.32% to 86.80%), total alkaline-rich(3.84% to 7.63% of K₂O+Na₂O), high Al₂O₃(8.59% to 13.70%), low MgO, CaO, TiO₂ and MnO. The geochemical characteristics of REE and trace elements are similar to those of A-type granite. The characteristics of low Ti/Y, Nb/Y and Ti/Zr, high Rb/Nb and Rb/Y and strong depletion in Sr and Eu indicate that the rhyolitic magma was originated from partial melting of basaltic upper crustal materials. Combining with the regional researching results, it is suggested that the rhyolite was formed in an intra-plate anorogenic extensional setting.