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

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.