The carbonaceous pelitic rocks in Changri Formation of Ogcheon Group have been studied by XRD and stable isotopic ratio determination and the zonation of metamorphic grade based on the graphitization has been carried out also. The distribution of the graphitizing degree is slightly inconsistent with the mineral zones of the studied area. The graphitizing degrees of the studied area by Tagiri's index are ranged from 31 to 100 which show some variance between ordered and disordered graphite. The maximum load pressure about 5.5 Kbar is estimated from the grid of graphitizing degree in the P-TGD diagram. The temperatures of graphitization can be estimated to 350°C~550°C from the P-TGD diagram and isotope geothermometer of carbon in the intercalated crystalline limestones. The stable isotope study on the black slates and phyllites of the studied area shows that the sources of carbon are similar with that of Paleozoic anthracites and coaly shales of Taebac coal fields.
Na et al. (Tue,) studied this question.