1988 Volume 38 Issue 209 Pages 247-262
In eastern Chugoku and western Kinki regions there are a number of stratiform sulfide ore deposits in Carboniferous and Permian submarine volcanic rocks and their metamorphic equivalents. They can be classified into three groups: (1) ore deposits in Carboniferous basic schist of the lower formation of the Maniwa Group of the Sangun metamorphic zone (Besshi-type stratiform sulfide ore deposits); (2) ore deposits in Permian basic schist and basic volcanic rocks of the lower formation of the Maizuru Group (Besshi-type stratiform sulfide ore deposits); (3) ore deposits in Permian acidic volcanic rocks of the middle formation of the Maizuru Group (Yanahara-type stratiform sulfide ore deposits). All ore deposits were folded three times: Late Paleozoic to Early Triassic (Sangun metamorphism), Middle Triassic and Jurassic ages. The Yanahara and Fukuzawa ore deposits were also influenced by contact metamorphism caused by Cretaceous granitic rocks. These ore deposits show a remarkable uniformity in sulfur isotope ratio, ranging from +0.6 to +2.99‰, despite the differences in age and acidity among the host volcanic rocks.
Both the Besshi-and Yanahara-type ore deposits are volcanic exhalative in origin. The Besshi-type ore deposits are genetically related to basic submarine volcanism, whereas the Yanahara-type ore deposits are related to acidic submarine volcanism.
