Before Later Proterozoic era, in this area more than two times of thermodynamicmetamorphism took place.
在晚元古代以前该地区至少发生过两次热动力变质作用。
2
In the bottom of coal measures is an acidic intrusive body, it is direct heat source of metamorphism, and provided the conversion of lignite to bituminous coal with thermodynamic power.