Petrogeochemical Study on the Igneous Rocks of Southwestern Part of the Sangju Area

상주(尙州) 남서부(南西部)에 분포(分布)하는 화성암류(火成岩類)에 대(對)한 암석지화학적(岩石地化學的) 연구(硏究)

The purpose of this study is to clarify the nature of the differentiation and petrogenesis of igneous rocks in comparison with experimental results based on petrological and geochemical criteria. Study area is composed of the Precambrian granitic gneiss complex, Triassic meladiorite and biotite granodiorite, Jurassic biotite granite, and Cretaceous quartz porphyry. According to the data of EPMA, the clinopyroxene and orthopyroxene of meladiorite come under salite and hypersthene, respectively. Such results suggests that meladiorite is incipient differentiated products of basic magma under slow cooling condition. The petrochemical data of variation diagram of major element oxides vs. silica and of trace element oxide vs. silica, AMF triangle diagram and trace elements suggests that igneous rocks of study area are plutonic rocks belong to calc alkali rock series of the source of comagma intruded-emplaced in the order of meladiorite, biotite granodiorite and biotite granite by fractional crystallization of magma.