Petro-geochemical characteristics and tectonic significance of Late Triassic volcanic rocks in Yanbian Area, northeastern China

The Late Triassic volcanic rocks in Yanbian Area are mainly composed of andesite,rhyolite,and minor basaltic andesite. The petro-chemical and geochemical data of the volcanic rocks indicate that they belong to subalkaline series and show the evolutional trend of calc-alkaline volcanic rocks, and are characteristics of the medium-K to high-K calc-alkaline series. The rock association, major and rare earth element data of the Late Triassic volcanic rocks suggest that they could be formed under the extensional environment in active continental margin. The formation of Late Triassic volcanic rocks in Yanbian region implies the beginning of the subduction of the Paleo-Pacific plate beneath the Eurasian plate and the end of the Paleo-Asian tectonic system.