| PDF: | |
| Time: | 2007 |
| Journal: | Journal of Jilin University (Earth Science Edition) |
| Volumn: | 37 |
| Issue: | 6 |
| Pages: | 1064-1073 |
| Type: | Other |
| Author: | Pujun Wang,Yanming Pang,Huafeng Tang,Yulong Huang,Changqing Zheng |
Abstract: | Compared with modern volcanic eruption types and volcanic structures, two kinds of paleo-volcanic edifices of the lower Cretaceous Yingcheng Formation (K1y) periods were recognized and described in the Songliao Basin based on their lithology, facies and vertical successions. They are basaltic and rhyolitic respectively. The basaltic volcanic edifices of the K1y are mostly shield volcanoes, with features of shield shape and gentle slopes less than 10°, of volcanic thickness of 200 m to 500 m, and of height difference from 100 m to 250 m. Vertical succession from bottom to top is from pillow lava and aa (with thickness proportion of 30%), to lava with vesicle and amygdule and also massive lava (with thickness proportion of 70%). Like Hawaiian, eruption of the basaltic type is mostly effusive and hydrothermal breccias were often developed around the conduit. On the other hand, the vertical sequence of the rhyolitic volcanic edifices is with three layers in a 300 m to 700 m interval. The bottom is composed mostly of pyroclastic breccia (explosive lava) (30% thickness), characterized by base-surge deposits with Pelean eruption. The middle layer is composed mostly of effusive rhyolites with vesicles, lithophysas and flow banding (60% thickness). Domes of extrusive perlite can also be found in the middle member, especially around calderas. The eruption type is Strombolian-like. The top layer is composed mostly of explosive granule tuff (sometimes stratiform) (lacustrine deposit of ash, 10% of thickness), with an eruption type of Plinian. Rhyolitic edifices is characterized by mound shape, relative evaluation of 200 m to 300 m and slope often more than 15°, thus belonging to stratovolcanoes |