ABSTRACT

Four K-Ar age determinations were made on the following materials in the Tungsten Province in the Inner Zone of Southwest Japan: biotite from the Koyo hydrothermal replacement Cu veins (Hiroshima Prefecture); sericite-bearing specimens from the Higasa Au-Ag veins (Okayama Prefecture); Okura Cu-Pb-Zn veins (Tottori Prefecture); and Yabu Ag veins (Hyogo Prefecture). They range from 85.1 to 68.9 Ma, which fall within the range reported by SHIBATA and ISHIHARA (1974) for the tungsten deposits in the Tungsten Province. It is pointed out that the base metal mineralization such as associated with copper took place later than the major tungsten mineralization, but somewhat earlier than the precious metal mineralization and the base and precious metal mineralization in and around the well-known Ikuno-Akenobe Province, Hyogo Prefecture.