Tholeiitic and Alkaline Basaltic Lavas of Wang-Tian’e and Changbaishan Volcanoes (Northeastern China): Timing and Genetic Relationship

Changbaishan and Wang-Tian’e volcanoes of Changbaishan area (Northeast China) were formed with a slight time gap in the last four million years. Wang-Tian’e volcano was formed at 3.8–2.7 Ma; the activity of Changbaishan volcano began at the Baishan stage about 1.6 Ma ago. In contrast to the trachybasalt–pantellerite bimodal association of Changbaishan volcano, Wang-Tian’e volcanic rocks are mainly tholeiitic basalts and much less often trachytes and alkaline rhyolites. An alkaline basalt flow has also been recorded on the northern and northeastern slopes of Wang-Tian’e volcano. Our petrological, geochemical, and geochronological data show that the occurrences of tholeiitic and alkaline basaltic magmatism in Changbaishan volcanic area were not synchronous, and the eruptive products of Wang-Tian’e and Changbaishan volcanoes belong to different petrochemical series. The rocks of Wang-Tian’e volcano itself are products of tholeiitic magmas. The alkaline basalt flow is much “younger” (<1.3 Ma) and appeared during the formation of the shield basement of Changbaishan volcano. The alkaline basaltic lavas on the northeastern slope of Wang-Tian’e volcano spread down into the valley as an extensive volcanic flow, forming a single volcanic cover together with the coeval rocks of Changbaishan volcano.