2013 Volume 52 Issue 1 Pages 23-31
The Besshi copper mine in Niihama City, central Shikoku, produced 700,000 tons of copper from 1691 to 1973, contributing to Japan's economic development and supporting the prosperity of the Sumitomo Group and Niihama City. A unique industrial heritage with many historical buildings remains in the Besshi area. Many bedded cupriferous iron sulfide deposits occur closely associated with basic schist in the Cretaceous Sanbagawa high-P/T metamorphic belt. The Sanbagawa belt was an accretionary complex derived from oceanic crust with pelagic sediments and trench turbidites. The Besshi deposit is the largest cupriferous deposit in Japan, and the tabular ore body of the massive sulfide ore occurs between basic schist and quartz schist. The ore consists mainly of pyrite and chalcopyrite with accessories of sphalerite and bornite. The Besshi sulfide deposit is considered to have been the hydrothermal precipitate formed by the mid-oceanic ridge volcanism and have been accreted onto the proto-Japanese Island by underplating at great depth.
