Sulfur isotopic ratio,δ
34SCDT, was determined on 50 sulfide samples from the Cretaceous (with one Paleogene locality) granitic terrain of the Kitakami Mountains, and the data, together with 8 analyses already published, were examined in view of the ore genesis. The studied ore deposits and quarries are 37. The δ
34S values are highest in molybdenite deposits, as -0.5 to +3.6 ‰δ
34S. The δ
34S values of base metal deposits, which are mostly skarn type, vary more widely than those of the molybdnite deposits, ranging from -3.4 to +5.5 ‰δ
34S. Tungsten and gold deposits, mostly of vein type, are hosted in the intruded sedimentary rocks and have low and widely varying δ
34S values (+2.8
~-16.7 ‰). Influence of biogenic sulfur from the Permian host pelitic rocks is considered for the low values of the Higashi-iwai (Au-W) and Masunai (Au) deposits. The δ
34S values of the granitoid-hosted molybdenite are averaged as +0.7 ‰, which is similar to +1.5 ‰δ
34S of the averaged rock sulfur value of the Tono and Miyako plutons. This and lower δ
34S values of the Kitakami sulfides, as compared with those of the Mo Province of Southwest Japan, may be correlated to a low fO2 magnetite-series character in the Kitakami Mountains. The intrusion-related gold deposits are divided into high-Au/Ag type with low contents of associated sulfides and low Au/Ag type with high contents of the associated sulfides. The former has -13.8
~+2.8 ‰δ
34S, indicating biogenic sulfur from the host sediments in some ore deposits, while the latter values, being -0.8
~+5.5 ‰δ
34S, are more close to δ
34S value of granitoid sulfur, implying higher contribution of magmatic sulfur for the low Au/Ag type.
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