Geology and Mineralisation
The Minamikayabe area is situated in the Kameda peninsula in southwest Hokkaido, the northern part of the Northeast Japan Arc, where epithermal base and precious metal deposits cluster in association with the Neogene igneous activity. In the Kameda peninsula, Mesozoic sedimentary rocks (Toi Formation) underlie Middle Miocene submarine andesitic volcanic rocks (Kunnui Formation) and Middle to Late Miocene submarine sedimentary rocks (Shiodomarigawa Formation) (Hata and Tsushima, 1971; Hata and Uemura, 1983). These Miocene rocks are intruded by NNW-SSE trending basaltic dikes of Middle Miocene age, and WNW-ESE trending dacitic intrusions of Late Miocene age (Hata and Tsushima, 1971; Hata and Uemura, 1983). Andesitic rocks of Pliocene and Quaternary age cover these older rocks, forming a NW-SE trending volcanic chain (Watanabe et al., 1996). Major Quaternary volcanoes in the chain include Komagatake, Yokotsudake, Maruyama and Esan from northwest to southwest. The Minamikayabe area is located near to the southeastern end of the volcanic chain (referenced from Watanabe et al 1996).
The Minamikayabe advanced argillic alteration lithocaps represent significant exploration targets for shallow-level epithermal gold and deeper porphyry copper-gold deposits. The Osorezan gold-bearing, hot spring-volcanic complex serves as a possible modern analogue for the Pliocene Minamikayabe stratovolcano.