Abstract:Sulfides from late Cretaceous-Paleogene ore deposits of the Inner Zone of Southwest Japan were analyzed for 34 S/ 32 S ratios (δ 34 SCDT values) on 5 samples from the Ryoke Belt, 18 from the Sanyo-Naegi Belt, 15 from the Uetsu-Kanto District and 47 samples from the Sanin-Shirakawa Belt. Together with the published data, the average δ 34 S values are calculated for individual deposits of the whole region; 109 localities for the ilmenite-series granitic belt and 56 localities for the magnetiteseries granitic belt.The sulfur isotopic ratios vary regionally rather than with sulfide species or types and commodities of the ore deposits. The δ 34 S values are generally negative in the fore-arc, ilmenite-series belt, and positive in the back-arc, magnetite-series belt. This regional variation is considered to reflect the ilmenite-/magnetite-series pairing of the genetically related granitic or volcanic activities, in which the positive δ 34 S ore sulfur was derived from a deep igneous source, but the negative δ 34 S sulfur was originated in biogenic sulfur of the accreted sedimentary complex. Within each terrane, δ 34 S values and mineral commodities vary locally, which is called domains in this paper. A few negative δ 34 S minima are observed in the Kinki, Hiroshima and Mino domains. These anomalies may have been brought by the most sediments-dominant granitic magmas generated within the accretionary sedimentary complex.The paired δ 34 S belts, called the Japanese-type pattern, may be unique to island arcs where their fore-arc sediments have been accreted in the arc-front associated with the back-arc rifting.

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Soil and stream sediments were studied geochemically around the Mau Due ore deposits of the northernmost Vietnam. The ore deposits are fracture-filling type occurring in Devonian sediments composed mainly of impure calcareous sediments. The chemical elements brought up by the mineralizations are mainly S and Sb, and small amount of As and base metal. The analyzed surface samples were collected in the wet season (May to September) and the dry season (October to April).Sb contents of surface materials are sporadically high in the soil samples, and have smaller variation in the stream sediments than in the soil samples. Sb contents of the soil of the wet season, 932 ppm Sb in the average, are higher than the average of 342 ppm Sb of the dry season. The Sb contents are much higher in the stream sediments, averaged as 2,536 ppm in the wet season and 2,504 ppm in the dry season.Generally speaking, As contents of the soil are positively correlated with Sb contents, but the amounts are much lower than the Sb contents, averaged as 29 and 26 ppm in soil of the wet and dry seasons, respectively, but higher as 68 and 67 ppm in the stream sediments. These abundance data of Sb and As are best explained by both elements are present finest grained sulfides in the soil and river sediments. The Devonian host rocks may be originally high in the Sb contents, as compared with the Japanese eugeosynclinal sediments.

Mill concentrates of ore sulfides from three magmatic-hydrotherml ore deposits were studied for δ 34 S at the granite-hosted Xihuashan deposits, and carbonate-hosted Shizhuan and Huashaping deposits. These ore deposits occur in the South China Fold System, which is composed of mid-Paleozoic "miogeosynclinal" sediments dominant in carbonates toward the Devonian age. Averages of the ore sulfides are -0.9 permil for the Xihuashan, +7.0 permil for the Shizhuan and +13.2 permil for the Huashaping deposits. Endogranitic ore sulfur of the Xihuashan and the Shizhuan deposits are considered magmatic, derived from by ca.+2 ‰ δ 34 S granitic magma, but the carbonate-hosted ore sulfurs at the major part of the Shizhuan and Huashaping deposits are much higher than those expected from rock sulfur δ 34 S values of the Yanshanian granites of the South China Fold System. Thus, addition of 34 S-enriched sulfur into the ore solutions is considered.Devonian and Carboniferous carbonates of the South China Fold System are very high in the δ 34 S values of structurally substituted sulfate (SSS) sulfur, averaged as +25.7 and +15.7 permil, respectively, which are higher than the reported values from other areas of these ages. The SSS contents of the Paleozoic carbonates are very low at present, but recent carbonates contain typically 0.1 to 1 % equivalent sulfate. The very low SSS contents in the wall rock carbonates and high δ 34 S values in the ore sulfides may have been resulted from carbonate SSS extracted during recrystallization and somehow mixed with magmatic ore fluids when the granitic magmas intruded, then precipitated as the ore sulfides.

Molybdenite discovered in a pegmatitic dikelet in a quarry exposure of the Busetsu Granite in Okazaki City was dated at 76.4±0.3 Ma using the Re-Os method. This age records the final stage of solidification of the Busetsu Granite and agrees well with previously reported CHIME monazite ages.