Sulfur isotope rations of sulfide minerals from the deposit of the Tsuchikura mine, Shiga Prafecture, Japan

Sulfur isotope rations of sulfide minerals in the ore specimens from the deposit of the Tsuchikura mine are distrib-uted in a range from -0.8 to 5.4%, mostly from +0.5 to 3.0%, close to the previous data (from +1 to +3%) by Miyake and Sasaki (1980). The distribution range is also similar to the major Besshi-type deposites of the Sambagawa terrain. Sulfur isotope fractionation between coexisting pyrite and chalcopyrite is not uniform. This may be largely due to spatial tearrangament of the initial orebodies to the present form. Sulfide minerals mostly pyrite from host rocks (siltsones, sandstones, basaltic rocks) exhibit remarkably low δ34S values ranging from -49.3 to -2.6%, dis-tinctly different from the δ34S values for sulfide minerals of ores. The low δ34S values may indicate the bacteriogenic origin of host rock sulfides, although it seems peculiar that basaltic rocks also have extremely low δ34S values.