Abstract: Petrology， geochemistry characteristics of the Hannuoba basalts distributed in Pingzhuang—Yuanbaoshan basin in eastern of Chifeng， Inner Mongolia were studied. The results showed that the volcanic rocks are dominated by basalts and minor sedimentary tuff. The petrologic compositions of basalts are homogeneous， content of the main elements change rarely， the basalts is characterized by higher titanium， lower aluminum and high Na₂O content，lower K₂O content. The total amounts of REE are lower， LREE is enriched， and there are weak Eu and weak Ce negative anomaly for Hannuoba basalts. The basalts are obviously enriched inlithophile elements (Rb，Ba，Th，K，Ta， LREE etc.)， and depleted in high field-strength element(U，HREE)as well as compatible elements (Co， Ni， Cr etc.). The Hannuoba basalts belong to the tholeiitic basalt series， and the source region of volcano rock is the asthenospheric upper mantle.The Hannuoba basalt formed in a continental rift tensile environment which is the product of continental intraplate stable tectonic environment.

Key words: Chifeng, Pingzhuang—Yuanbaoshan basin, geochemistry, Tholeiitic basalt, continental rift