Abstract: Petrology， geochemistry， isotope geochronology of the volcanic rocks distributed in PingzhuangMachang basin of Jianping of western Liaoning were studied. The results showed that the volcanic rock is the Cretaceous. The volcanism of Yixian formation may be divided into two subcycles. The volcanic rocks mainly consist of rhyolites， trachyte and trachyandesites. The volcanic rocks belong to the highK calcalkaline magmatic series. The volcanic rocks are characterized by components of high SiO2， Al2O3， K2O and Na2O， and comparatively low MgO and TiO2. The volcanic rocks are obviously enriched in large ion lithophile elements (K， Rb， Sr， Zr， Ba， Pb and Li)， and depleted in high fieldstrength element (Nb， Ti， P)as well as compatible elements (Co， Ni， Cr and V). The volcanic rocks is rich in LREE. There is a slight negative Eu anomaly and no Ce anomaly. A detailed geochemical discrimination of the selected elements allowed us to identify that the volcanic rocks of Yixian formation mainly derived from the partial melting of lower crust materials， but also has been contaminated by upper crustal materials during its ascent process in some degree. The volcanic rocks of Yixian volcanic cycle were generated in response to lithosphere inhomogeneous extension in the continental intraplate orogenic belt. They have the basic characteristics of continental intraplate volcanic rocks.

Key words: Jianping country, Yixian formation, geochemical discrimination, lithosphere extension, intraplate organic belt