K-Ar Ages of Some Ore Deposits in Japan

Abstract

The K-Ar ages of the minerals from several ore deposits in Japan were determined as follows :
Adularia from the Au-Ag-quartz vein of the Seikoshi mine,
Shizuoka Prefecture 3.7 m.y.
Adularia from the Au-Ag-quartz vein of the Takatama mine,
Fukushima Prefecture 8.4 m.y.
Adularia from the Cu-quartz vein of the Ani mine,
Akita Prefecture 11 m.y.
Orthoclase from the Ag-quartz vein of the Omidani mine,
Hyogo Prefecture 66-68 m.y.
Orthoclase and muscovite from the W-Sn-Cu-quartz vein of Kaneuchi mine,
Kyoto Prefecture 73 m.y. and 93 m.y., respectively
The ages of the mineralization of the Takatama and Seikoshi mines are considered to be the Pliocene and the late Miocene, respectively.
The K-Ar age of adularia from the Ani mine is similar to that of orthoclase and biotite of the Taishoko granitic rock where the major ore veins occur. The vein-type deposits of this mine are probably related to granitic intrusion of the middle Miocene.
The K-Ar age of the Omidani ore deposits is similar to that of the Ikuno and Akenobe xenothermal-type ore deposits. From the K-Ar dating as well as the zonal distribution of hypogene minerals, the Omidani silver deposits are thought to constitute an outer zone of the Ikuno-Akenobe metalliferous district. The mineralization seems to be a part of the late Cretaceous to Paleogene granitic activities.
The muscovite age of the tungsten deposits of the Kaneuchi mine belonging to the hypothermal or pegmatitic vein-type coincides with the isotopic ages of the granodiorite where the Otani tungsten deposits occur. It is inferred that the deposits of the Kaneuchi mine are genetically related to the late Cretaceous granitic activities.