Preliminary study on Quaternary volcanoes in the Halaha River and Chaoer River area in Daxing'an Mountain range

28 Quaternary volcanoes,which scattered along a Quaternary NE strike fault,are found in the area of Halaha River and Chaoer River,middle of Daxing'an Mountain Range.Quaternary volcanic rocks in this area,mainly alkaline basalt,cover an area of ca.1000 km~2.These volcanoes can be divided into two stages:Holocene volcanoes and Pliocene volcanoes.Both magmatic eruptions and phreatomagmatic eruptions are found in this area.The magmatic eruptions form a series of products,including scoria cones,tephra fallout deposits,and many kinds of lava(e.g.aa lava,pahoehoe lava and block lava).Typical fumarolic cones and lava hillocks are found in the lava.The phreatomagmatic eruptions have typical base surge deposits,which are characterized by parallel bedding and staggered bedding.Volcanic activity in this area form many volcanogenic lakes.According to the difference of lake forming,they are divided into four types:Crater lake,maar lake,volcanic dammed lake,collapse lava lake.Two conflict factors,water and fire, coexists harmoniously in the volcanic area,adding a splendid landscape to the Aershan Volcano and Warm Spring National Geopark.