ABSTRACT

Using K-Ar method, five ages were measured on the minerals: hornblende from the Ushirodani Cu-Zn skarns, Tottori Prefecture (60.7±3.1, 60.8±1.9 Ma); muscovite from the Kuga and Kiwada scheelite skarns, Yamaguchi Prefecture (93.6±2.9 and 94.0±2.9, 101.6±5.0 Ma, respectively). The close time-space relations reveal that the Ushirodani Cu-Zn skarns in the Molybdenum Province have a genetical connection with the granitic magmatism of magnetite-series, while the scheelite skarns such as those of Kuga and Kiwada in the Tungsten Province are genetically related to the ilmenite-series granitoids. Taking consideration of the previously reported ages of other skarn deposits, it is concluded that the ore-bearing skarns, as well as other types of ore deposits in the Molybdenum Province are definitely younger than those in the Tungsten Province, reflecting the difference in ages of granitic magmatism responsible for the mineralization.