K-Ar ages for the Yatani Pb-Zn-Au-Ag vein-type deposits and Otoge kaolin-pyrophyllite deposits, Yamagata prefecture, northeastern part of Japan

Abstract

Three samples of adularia from the different veins of Yatani Pb-Zn-Au-Ag deposits give 3.61±0.27, 3.37±0.13, and 3.25±0.26 Ma. One sample of sericitized rock from Otoge kaolin-pyrophyllite deposits gives 5.16±1.95 Ma. These results indicate that (1) Age of Au-Ag mineralization in the Yatani deposits is nearly same to that of Pb-Zn mineralization in the same deposits, (2) Intense hydrothermal activities occurred at ca. 5±2 million years ago in the Yatani-Otoge mining district, and (3) Vein-type mineralizations occurred in Green tuff region of northeastern part of Honshu during a period of ca. 15-3 Ma.