Abstract: Xilinhot-Abaga volcanic cluster is located in Xilin Gol League of Inner Mongolia Autonomous Region,and it is in the centre of Daxinganling-Datong volcanic eruption belt. There are more than 300 Quaternary basaltic volcanoes of different types. Maars are found for the first time there,with Haotewula in the southeast of Abagaqi,Chelewula and Esigewula in the northwest of Abagaqi being the most representative. They all have large scale,and the diameter of cone is generally 3～4km,the largest is up to 6.5km. They have relatively intact structure,similar two-ringed mountain landscape and obvious phreasic eruption which contains strong phreatomagmatic eruption at the earlier stage,later weak magmatic eruption and at last basaltic lava overflowing phase. This eruption sequence reflects the interaction between magma and groundwater,the change in intrusive speed and the flow-out rate of magma. The sand and gravel of Middle Pleistocene depositing in the valley are covered by basal surge deposits. The TL age of sandstone-shale inclusion which was found in the spattering deposits close to crater is(0.112±0.0096)Ma,which indicates that the eruption times of the maars are early Late Pleistocene.

Key words: phreatomagmatic eruption, base-surge deposits, maar, Xilinhot-Abaga volcanic cluster

摘要： 锡林浩特-阿巴嘎火山群位于内蒙古自治区锡林郭勒盟,处于大兴安岭-大同新生代火山喷发带中段。火山群内发育300余座不同类型的第四纪玄武质火山,其中玛珥式火山属首次发现,以阿巴嘎旗东南部的浩特乌拉、西北部的车勒乌拉和额斯格乌拉玛珥式火山最具代表性,其火山规模较大,锥体直径一般为3～4km,大者约6.5km。火山结构较完整,具有相似的双轮山地貌景观和明显的阶段性喷发过程,喷发阶段早期为强烈的射汽-岩浆爆发,晚期均转变为弱岩浆爆发,最后为玄武质熔岩流的溢出。这种喷发序列反映了岩浆与水相互作用以及岩浆上升速度和溢出率变化的过程。火山喷发形成的基浪堆积物覆盖在中更新统河谷砂砾石之上,其中近火口溅落堆积物中上新世砂泥岩 "包体"的热释光年龄为(0.112±0.009 6)Ma,表明玛珥式火山喷发时代属晚更新世早期。

关键词: 射汽-岩浆爆发, 基浪堆积, 玛珥式火山, 锡林浩特-阿巴嘎火山群