Petrological and Geochemical Studies on Quartzite from the Jangsan Quartzite Formation in the Bonghwa-Gun, Korea

경북(慶北) 봉화군에 분포(分布)는 장산규암층(壯山硅岩層)의 암석학적(岩石學的) 및 지구화학적(地球化學的) 연구(硏究)

The Jangsan Quartzite is a basal unit of the Cambro-Odovician sequence, in Socheon-Myeon, Bonghwa-Gun, Gyeongsangbug-Do, South Korea, was petrologically and geochemically investigated. The quartzite consists mainly of quartz and muscovite, assosiated with tourmaline and graphite. The quartzite shows white and/or gray color and various green color in hand specimens. The white and gray colored rocks have very low vanadium contents, but a dark green colored rock contains 8960 ppm vanadium. The muscovites in the quartzite show colorless and green color, of which green ones range from pale blue green to pale green. The dark green colored muscovites have above 8 wt. % vanadium and pale green ones have 1-3 wt. % vanadium. Vanadium contents in moscovite increase with decreasing $Al^{v1}$ contents. It suggests that vanadium substitutes for octahedral aluminium in moscovite. In general, it tends to large volumes of muscovite (up to 14 modal %) in deep green colored rocks, and high vanadium contents in their muscovites. Most of the moscovite flakes occur along the quartz boundaries and some are enclosed by quartz grain. The moscovite grains intergrowth each other in the former. The mouscovite aggragates are divided into two types on the basis of their intergrowth(cut) times. Two cut times and one cut time are named T type and D type, respectively. The T type is mainly distributed at western part (near of the Chunyang granite), whereas the D type is distributed from middle to estern part(near the Janggunbong) of the formation. The boundary is consistent with metamorphic isograd between andalusite and sillimanite zone by Ahn et. al. (1993).