Copper-lead-zinc mineralization at the Hayakawa and Shakako deposits, Jokoku-Katsuraoka mining area, southwestern Hokkaido, Japan.

Abstract

This paper summarizes macrostructures of individual ore bodies, mineral assemblages, mineralization stages, and oxygen isotopic data for quartz from veins and wall rock for copper-lead-zinc mineralization at the Hayakawa and Shakako deposits. Chalcopyrite-pyrite-tetrahedrite-galena-sphalerite-bearing quartz veins (Cu-Pb-Zn quartz veins) and galena-sphalerite-bearing quartz veins (Pb-Zn quartz veins) occur at the Hayakawa and Shakako deposits. The Cu-Pb-Zn quartz veins formed earlier than the Pb-Zn quartz veins. The minerals in the Cu-Pb-Zn quartz veins include chalcopyrite, pyrite, tetrahedrite-tennantite, galena, sphalerite, enargite, bournonite, semseyite, hessite, kesterite, arsenosulvanite, Cu-Fe-Zn-Sn-S mineral, tetradymite, aikinite, quartz and apatite. The minerals in the Pb-Zn quartz veins are galena, sphalerite, pyrite, chalcopyrite, tetrahedrite, electrum and quartz. FeS content of sphalerite decreases from the earlier to later stages of mineralization. Distinct compositional heterogeneity between Sb and As is recognized within a grain of tetrahedrite-tennantite. The δ18O values for quartz in Cu-Pb-Zn quartz veins at the Hayakawa deposit range from 1.4 to 3.1 per mil. The value for quartz in Cu-Pb-Zn-quartz veins at the Shakako deposit is 1.9 per mil. The calculated δ18O values (-10.1 to -3.3 per mil) of ore fluids responsible for the formation of the Hayakawa deposit are lower than sea water and primary magmatic water. Therefore, we suggest that Cu-Pb-Zn quartz veins of the Hayakawa and Shakako deposits originated from ore fluids of meteoric water under a subvolcanic environment.