CHEMISTRY OF VOLCANIC ROCKS OF TIAOJISHAN FORMATION IN BEIPIAO-YIXIAN, WESTERN LIAONING,CHINA

The Mesozoic volcanic rocks are broadly distributed in Western Liaoning Province. The Tiaojishan formation,developed in Beipiao-Yixian area, Western Liaoning, may be divided into three members. And the Tiaojishan volcanic cycle can be subdivided into two sub-cycles.The volcanic rocks belong to high-K calc-alkaline series,with SiO₂ of 53.67% to 75%, Al₂O₃ 13.15-19.16, K₂O+Na₂O 5.17, and δ 1.46-6.83. The ΣREE of the volcanic rocks of Tiaojishan volcanic cycle is high,with rich LREE.The distribution patterns are right-incline, with a slightly low Eu negative abnormality and low Ce abnormality.Studying shows that the volcanic rocks of Tiaojishan volcanic cycle were generated in response to lithosphere extension in the continental intraplate orogenic belt.The lithogenesis take partial melting as a major process.