| PDF: | |
| Time: | 2007 |
| Journal: | Journal of Jilin University (Earth Science Edition) |
| Volumn: | 37 |
| Issue: | 1 |
| Pages: | 65-72 |
| Type: | Other |
| Author: | Yulong Huang,Pujun Wang,Zhiqiang Feng,Rui Shao,Zhenhua Guo,Zhongjie Xu |
Abstract: | Modern volcanoes can be classified as three main forms in shape (Shield-shape,cone-shape and dome-shape) and seven different types.In surrounding sections and northern faulted depression in the Songliao Basin,there are mainly four types of volcanoes such as shield volcano,composite volcano,pyroclastic cone and lava dome.Shield volcanoes are built almost entirely of fluid lava flows,with little explosive pyroclastics.Composite volcanoes are built of flow layers alternating with pyroclas-tics,thus the alternate sequence of effusive and explosive facies is well developed.Pyroclastic cones,the simplest type of volcano,consist of particles and blobs of congealed lava from a single vent,mainly of explosive facies.Lava domes are formed by relatively small,bulbous masses of the lava which is too viscous to flow long distance,therefore,the lava piles over and around its vent by extrusion.Eruption patterns here mainly include effusive,extrusive and volcanic vent facies.In the Songliao Basin the buried volcanic edifices is characterized by slope angle ranging from minimum 3° to maximal 25°,bottom diameter from 2 to 14 kilometers and volcanic rock thickness from 100 to 600 meters.The buried volcanic edifices may cover an area of 4 to 50 sq.kilometers for each.As a whole,buried volcanoes of the northern Songliao Basin appear numerous,individually small and are controlled by regional faults.They are normally featured with crack and multi-central type eruptions,volcanic products of different vents commonly pile up each other.Volcanic lithology and lithofacies are the main factors that control the types and forms of the volcanic apparatus in the Songliao Basin |