Essential Characteristics of Volcanic Rocks of Yixian Formation and Discussion on Tectonic Setting in Chaoyang Basin, Western Liaoning

Volcanic rocks of Early Cretaceous Yixian Formation were widely distributed in western Liaoning. The Yixian Formation in the Chaoyang basin can be divided into two subcycles from bottom to top. The first subcycle is composed of basalt, basalt andesite and andesite. The second subcycle is composed of trachyandensite and trachyte. The volcanic rocks are characterized by high SiO2, Al2O3, K2O and Na2O, and comparatively low TiO2 components. The volcanic rocks are obviously enriched in incompatible elements (K, Rb, Sr, Zr, Ba, Pb, Li etc.), and depleted in compatible elements (Co, Ni, Cr, V etc.). The volcanic rocks are rich in LREE. There is a slight low Eu negative abnormality and low Ce negative abnormality. Based on t he studies of petrology and geochemistry, volcanic rocks of Yixian Formation belong to the high-K calc-alkaline magmatic serious. Comprehensive study of regional structures and geochemistry of volcanic rocks, the volcanic rocks of Yixian Formation were generated in the environment of lithosphere inhomogeneous extension, as a product of the intraplate orogeny of Yanshan Mountains.