Distribution of sulfur isotopes in the Ryusei vein of the Akenobe mine, Hyogo Prefecture, Japan

Abstract

Abstract-Sulfide samples (mostly chalcopyrite with some sphalerite and bornite) from the Ryusei vein of the Akenobe mine exhibit a narrow spread in S34S value ranging from -4.4 to -0.4%o. The range is lower than those of other Japanese sulfide deposits so far studied. The frequency diagram of S34S values for chalcopyrite indicates that the 534S distribution is bimodal; one peak at -3.0 to -2.5%o and the other at -1.5 to -0 .5 %o. This suggests that chalcopyrite in the Ryusei vein was formed in at least two different stages of mineralization.Of 9 sphalerite-chalcopyrite pairs studied (including 2 pairs from different veins), 8 pairs are isotopically in disequilibrium; sphalerite is up to 2.7 %o lighter than coexist ing chalcopyrite.From the isotopic and chemical equilibrium relationship between the aqueous and mineral species of the Cu-Fe-S-O system, S34S values of the ore-forming solutions were speculated to be rather similar to those of chalcopyrite (0 -5 %o).

Sulfur isotope ratios of some Japanese skarn deposits.

“…Because only little is known about isotope ISHIHARA (1977), and relatively reducing nature ratios of sulfide sulfur from Japanese hydro of the hydrothermal solutions responsible for thermal vein and skarn deposits (YAMAMOTO, these deposits, is supposed to be genetically 1974, 1976Kiyosu, 1977;Kiyosu and NAKAI, related to the nature of granitic magmas (S HI 1977;SASAKI and ISHIHARA, in press), the MAZAKI, in press). present writers have planned to determine sulfur isotope ratios of hydrothermal deposits as many OUTLINE OF ORE DEPOSITS as possible.…”