K-Ar Ages of the Jecheon Granitic Complex and Related Molybdenite Deposits in South Korea

Abstract

K-Ar age determinations were carried out on the Jecheon mass and adjacent rocks occurring in the Ogcheon Zone of South Korea. Biotites separated from the Jecheon mass yield ages of 179, 169 and 159 Ma, confirming that the mass and the related molybdenum deposit were formed by the Daebo igneous activity. Muscovite from the Daehwa mine gives an age of 89 Ma and belongs to the Bulgugsa activity.
Muscovite from pegmatite near the Dangdu mine, which intrudes into the Ogcheon Group, gives a Precambrian age of 1720 Ma. Thus the original rocks of the Ogcheon Group appear to have a middle Proterozoic age.