| PDF: | |
| Time: | 2007 |
| Journal: | Journal of Jilin University (Earth Science Edition) |
| Volumn: | 37 |
| Issue: | 6 |
| Pages: | 1131-1138 |
| Type: | Other |
| Author: | Jinlong Li,Pujun Wang,Changqing Zheng,Huafeng Tang,Yanxiong Wu,Weihua Bian |
Abstract: | Rhyolite with columnar joints has been found in the lower Cretaceous Yingcheng Formation, in an uplift area of the southeastern Songliao Basin. The columnar joints in rhyolite are primary structural joint developed in a sub-volcanic sub-facies of volcanic conduit (extrusive) facies. The joints seen include horizontal, inclined and vertical ones. Their cross sections developed are anomalous tetragonal, pentagonal or hexagonal and are of medium to small size. Crypto-explosive breccia structures were well developed. The diameter of prisms is in proportion to the size of micro-fabric phenocryst. The primary genetic mechanism for the joints is the condensing shrinkage. Controlled by different factors, the eventual shapes of columnar joints are quite varied. |