Sources of alkaline and tholeiitic basaltic magmas of Changbaishan volcanic area (Northeastern China)

Abstract

Changbaishan volcanic area (China-North Korea) is located on the margin of the Eurasian continent within the large Cenozoic intraplate province of Central and Eastern Asia. Two large volcanoes Wangtian'e and Changbaishan of the area are situated 30 km from each other in Northeastern China. Basalts of Wangtian'e volcano belong to the tholeiitic rock series as well as basalts of Changbaishan volcano belong to the alkaline one. In this paper we use data on chemical and isotopic (Pb, Sr, Nd) composition of tholeiitic and alkaline basalts to reconstruct magmatic sources that participated in the tholeiitic and alkaline rock formation. Isotopic and geochemical features of tholeiitic and alkaline basalts of the Changbaishan volcanic area indicate the participation of three different sources in their formation. The formation of tholeiitic and alkaline melts of the Changbaishan volcanic area occurred within the mechanical asthenosphere-lithosphere boundary layer at a depth of 30–75 km in two stages. The first stage corresponds to the melting of supra-subduction peridotite of the lithospheric mantle and eclogite lenses resulted in the formation of tholeiitic melts that formed Wangtian'e volcano. As the eclogite was exhausted, the resulting tholeiitic melt reacted with fertilized mantle peridotite producting pyroxenite source. The second stage corresponds to the partial melting of pyroxenite together with peridotite of the asthenospheric mantle, which led to the appearance of alkali-basaltic melts that participated in the formation of Changbaishan volcano.