Significance of K-Ar age of bimodal volcanic rocks at Wangtian’e volcano, Changbaishan area

Abstract

Wangtian’e volcano, about 30 km south of Tianchi volcano is another large scale volcano center on the south slope of Changbaishan with its nearly 4 000 km2 area of volcanic rocks distributed over the border area of the Chinese side. Based on the field occurrence, petrology and K-Ar age dating of its volcanic rocks, it can be shown that the Wangtian’e volcano had experienced two developing stages of shield forming and cone forming, while its volcanic activities can be divided into three periods: Changbai period (? −2.87 Ma), Wangtian’e period (2.69–2.41 Ma) and Hongtoushan period (2.12 Ma). Its petrographic change goes from trachybasalt→ basaltic trachyandesite, trachyte→alkalic rhyolite, with a feature of bimodal volcanic rock combination similar to yet a bit different from that of Tianchi volcano, and is a new scene for study of volcanic magma evaluation of Changbaishan volcanoes.