Petrology and Petrochemistry of the Cretaceous Granites in the Southern Mungyeong Area

문경(聞慶) 남부일대(南部一帶)에 분포(分布)하는 백악기(白惡紀) 화남암류(花南岩類)의 암석학(岩石學) 및 암석화학(岩石化學)

The Cretaceous granites are widely distributed in the studied area, Mungyeong-Sangju, which belongs to the southwestern part of the Ogcheon Folded Belt. The granites are characterized by medium-coarse grained, spotted miaroles, partly flow textures of biotite, aplitic dykes and pegmatitic pockets with druse. From the major compositions, the granites indicate peraluminous, calc-alkaline, salic and late stage products of differentiation. In the view of normative compositions of Qz-Ab-Or and perthitic alkali feldspar, they were formed under 1-4kb and $426^{\circ}-456^{\circ}C$ in acqueous conditions. The K/ Ar biotite age shows $72{\pm}1$ Ma for this grante, corresponding to the igneous activity of the Bulgugsa Disturbance periods in the area. The above results represent that these granite bodies are differentiated from a single magma.