K-Ar Ages of Some W-Mo Deposits and Their Bearing on Metallogeny of South Korea

Abstract

K-Ar ages were determined on eight specimens from five W-Mo deposits in South Korea. Muscovites purified from tungsten ore and pegmatitic quartz vein of the Ssangjeon W deposits give ages of Proterozoic. Although biotite in pegmatitic quartz vein of the Ogbang W mine yields much younger age, the occurrences of the deposits in both mines are so similar that the Ogbang deposits seem to have been formed at almost the same time as the Ssangjeon deposits. Muscovites from the Garisan W-Mo and Jangsu Mo deposits give ages of about 170 Ma, and confirm wide distribution of W-Mo mineralization at early Jurassic time. The results for sericites from the Cheongyang W deposits are around 80 Ma, and are almost same as those of the Daehwa W-Mo and Sangdong W-Mo-Bi deposits. In South Korea, W-Mo mineralization is prior to Au-Ag mineralization in Jurassic time, whereas vice versa in Cretaceous time. At the northeastern end of the Ryeongnam massif, tin (-1800 Ma), tungsten (-1500 Ma) and gold (-1100 Ma) mineralizations are overlapped in Proterozoic time.