Gold abundance of Japanese granitoids-A preliminary report

Abstract

Twenty-four granitoids from three magnetite-series granitic terranes and three ilmenite-series granitic terranes were analyzed for gold by the neutron activation method. The gold values of the magnetite-series granitoids range from 0.4 to 7.1 ppb and the average is 4.3 ppb, while those of the ilmenite-series granitoids vary from 0.4 to 4.8 ppb and the average is 2.5 ppb. The higher values of the magnetite-series granitoids than the ilmenite-series ones may be attributed to the presence of rock-forming magnetite in the former series. The gold values appear to increase with the in-creasing of silica contents within the range of 61-76%. Magnetite-series granitic terranes are considered to be more favarable basement than ilmenite-series ones for Neogene gold mineralization of the Green Tuff region.