Study On Tectonic Quaternary Volcanoes In Arshan-Chaihe Area, Inner-Mongolia

The volcanic culuster of Arshan-Chaihe is located near the boundary of Hulun Buir Meng and Hinggan Meng in the northeast of Inner-Mongolia Autonomic Region. It belongs to the volcanoes belt of Datong-Daxinganling which was active in Cenozoic. From the mid-Pleistocene there happened lots of volcano eruptions, which formed a cluster strike northeast. The products of volcanoes covered the stratum of Jurrasic, and spreaded mainly in the valley of Chaoer river , Halaha river , Chai river and Dele river with a square of 2000 km~2.There are 3 phases of the volcanoes activity: mid-Pleistocene, up-Pleistocene and Holocene. All these volcanoes include cones and lavas. Although these volcanoes are comparatively small in size, they are well kept. Most of them are new-born .except one inherits previous volcano edifice. There are effusive volcanism as well as explosive volcanism which include magmatic fragmentation and phreatomagmatic fragmentation. Four types of volcanic edifices can be seen here: strombolian, Hawaiian, subplinian, maar; they constitute two volcanoes chains. The volcanic here is mainly alkali basalt.Mid-Pleistocene volcano eruptions are mainly phreatomagmatic eruptions, which includes the maar eruption and which is rare in Inner-Mongolia area. In up-Pleistocene, there happened fissure eruptions, fissure-point eruptions and point eruptions. And the eruption type is mainly the strombolian style. The Holocene volcanoes include the Moon pool, Zigong hill, Yanshan et al.The cluster of volcanoes are aligned generally in line, and apparently it is affected by the basement rifts. Most of the volcanoes are located at the cross of fractures. There are different directions of these fractures: NE,NNE,NW,EW and NS and all of these fractures behaves as normal faults and they are mostly tension fractures. These tension fractures are caused by vertical stress and they are seldom affected by lateral stess. This is a important character of the active structures of this area. The movement of the chamber may be the critical factor of the active structures of this area.The volcanic culuster of Arshan-Chaihe include some active volcanoes and they may erupt again. The research of the physical parameters can help to make the plan to deal with the possible disasters.