Petrochemical Study of Igneous Rocks Occurring in the Northwestern Part of Keumsan Area, Chungnam-do

Igneous rocks occurring in the northwesern part of Keumsan area, Chungcheongnam-do were studied petrogeochemically. The geology of this area is composed mainly of the Precambrian biotite gneiss, age-unknown Ogchon supergroup, Jurassic biotite granite, and Cretaceous volcanic rocks, pink feldspar granite and quartz porphyry. The biotite granite is gradually changes to leucocratic nature by going from center to periphery of the rock mass. It shows variation, with distance from the center, in chemical components: increase, whereas decrease. Based on geochemical data, the biotite granite and quartz porphyry belong to subalkaline series and I-type. They show calc-alkaline differentiation trend. The biotite granite shows little negative Eu-anomaly pattern, whereas quartz porphyry show marked negative Eu-anomaly pattern, indicating that quartz porphyry was evolved further, when compared with biotite granite.