J. Min. Peter. Econ. Geol. 85, 341-353, 1990 Copper-lead-zinc mineralization at the Hayakawa and Shakako deposits, Jokoku-Katsuraoka mining area , southwestern Hokkaido, Japan DAIZO ISHIYAMA*, HIROHARU MATSUEDA** and OSAMU MATSUBAYA*** * Institute of Mining Geology , Mining College, Akita University, Akita 010, Japan ** Department of Geology and Mineralogy , Faculty of Science, Hokkaido University, Sapporo 060, Japan *** Research Institute of Natural Resources , Mining College, Akita University, Akita 010, Japan 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 ƒÂ18O 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 ƒÂ18O 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. Molybdenite-pyrite-fluorite-bearing Introduction quartz veinlets and molybdenite-galena-spha- The Hayakawa and Shakako deposits are lerite-pyrite-calcite-gypsum (after anhydrite)- located in the Jokoku-Katsuraoka mining area, bearing veinlets occur in altered rhyolitic pyro- which is noted for its manganese resources in clastic rocks (the Fukuyama Formation) and Japan. Neogene mineralization is divided into porphyrite (Neogene age), which were recover five stages in the Jokoku-Katsuraoka mining ed from boreholes (55MADO-1 and 55MADO-2) area (Ishiyama et al., 1987). Chalcopyrite- 2 kilometers north of the Hayakawa deposit pyrite-tetrahedrite-galena-sphalerite-bearing (M. M. A. J., 1981). Fluid inclusion data indicate quartz veins of the Hayakawa and Shakako that this molybdenite formed in a volcanic deposits formed in the 2nd stage (copper-lead- environment at higher temperatures than man zinc mineralization) of the Jokoku-Katsuraoka ganese and base metal veins in the Jokoku mining area. mining area (Ishihara and Morishita, 1983). (Manuscript received, March 3, 1990; accepted for publication, June 19, 1990) 342 Daizo Ishiyama, Hiroharu Matsueda and Osamu Matsubaya 18O value of quartz is -4 .3 per mil, suggesting that H2O of ore fluid precipitating minerals in the veinlets were largely of meteoric water origin (Ishihara and Morishita, 1983). The same molybdenite-bearing quartz veinlets de scribed above also occur in altered diorite porphyrite 0.5 kilometers south of the Katsu raoka deposit (Narita, 1961). Preliminary studies on the Hayakawa and Shakako deposits have been made by some researchers. Bamba (1957) and Sawa et al. (1965) studied mode of occurrence of the veins and wall rock alteration at the Hayakawa and Shakako deposits. Sawa et al. (1965) reported fluorite occurrence in veins at the Hayakawa deposit. Enjoji and Takenouchi (1976) and Fig. 1. Location and geologic maps of the Haya Ishiyama et al. (1987) summarized homogeniza kawa and Shakako deposits (after M.M. A. tion temperatures of fluid inclusions in sphaler J., 1981). 1, Alluvium; 2, Fukuyama F.; 3, Matahachizawa F.; 4, Matsumae G. ite, quartz, and fluorite from the Hayakawa Chiisago F.; 5, Neogene intrusive rocks; deposit. However, there were few studies with 6, Deepseated Neogeneintrusive rocks; 7, respect to mode of occurrence of ore minerals Faults; 8, Manganese carbonate vein deposits; 9, Cu-Pb-Zn quartz vein and origin of ore fluid responsible for the forma deposits; 10, Boreholes. tion of the deposits. In this paper we will describe mode of occurrence and chemical com porphyry and quartz-diorite-porphyry of positions of ore minerals and also oxygen Neogene age (M. M. A.J., 1981; Ishiga and isotopic ratios for vein quartz and wall rocks . Ishiyama 1987). We will discuss genetic relationships among The Chiisago Formation, in ascending copper-lead-zinc mineralization at the Haya order, is composed of basic tuff and lava; lime kawa and Shakako deposits, molybdenum stone and/or dolomite rock; reddish, bedded - bearing base metal mineralization in the bore chert; dark, bedded chert; mudstone; and holes and manganese-lead-zinc-silver mineral- sandstone (Ishiga and Ishiyama, 1987). ization at the Matahachi deposit in the Jokoku- Although the Chiisago Formation is not Katsuraoka mining area. exposed in the immediate vicinity of the Haya kawa and Shakako deposits (M.M. A.J., 1981), Geologic setting the formation might occur several hundred The Jokoku-Katsuraoka mining area (Fig . meters beneath the Hayakawa deposit. 1), including the Hayakawa and Shakako The Matahachizawa Formation consists of deposits, consists, in ascending order , of late rhyolitic to dacitic tuff breccia with abundant Carboniferous to Jurassic Chiisago Formation mudstone and chert fragments. The Mataha of the Matsumae Group, Oligocene Matahachi chizawa Formation occurs locally around the zawa Formation, and Miocene Fukuyama For Matahachi deposit of the Jokoku mine. mation. These formations were intruded by The Fukuyama Formation is divided into stocks and dikes such as granodiorite- the Lower, Middle and Upper Members, and ƒÂ Copper-lead-zinc mineralization at the Hayakawa and Shakako deposits 343 The Hayakawa and Shakako deposits are situ unconformably overlies the Chiisago and Mata ated 2.5 kilometers southeast of the Matahachi hachizawa Formations (M. M. A. J., 1981). The deposit of the Jokoku mine. The Gamano Lower Member of the Fukuyama Formation sawa and Ishizaki deposits, similar to the consists mainly of dacitic pyroclastic rocks, Hayakawa and Shakako deposits, are located locally intercalated with mudstone and sand northeast of the Hayakawa deposit (Fig. 1). stone. The Middle and Upper Members con The Hayakawa mine produced a total of sist of andesite lavas and associated pyroclastic rocks (M. M. A. J., 1981). The Hayakawa 6,137 metric tons of crude ore during the years 1935, 1940, 1942 to 1943 and 1945. The ore deposit occurs in the Lower and Middle Mem bers of the Fukuyama Formation. Strata of yielded 45,810kg of copper, 185,500kg of zinc, 149,900kg of lead, 130,000g of silver and 975g the Fukuyama Formation trend N-S to NE of gold during this period (Sawa et al., 1965). SW and dip 20•‹to 40•‹E or W forming a gently Veins of the Hayakawa deposit generally folded structure with a fold axis trending N-S trend N80•‹E-S80•‹W and dip 70•‹NW. Strike to NNE-SSW (M. M. A. J., 1981). Many granodiorite-porphyry, diorite and length of these veins is about 800 meters (see Fig. 6 in Sawa et al., 1965). The veins reach a diorite-porphyrite stocks of Neogene age intrude the Fukuyama Formation. Gravity maximum width of 20 centimeters in the data suggest that similar Neogene intrusive deposit. The Shakako deposit is another part of the same vein deposit as the Hayakawa rocks occur deep beneath the eastern part of deposit and is located 200 meters west of the the Hayakawa deposit (M. M. A. J., 1981). Hayakawa deposit. Copper-lead-zinc mineralization of the Haya Post-depositional alteration of dacitic and kawa and Shakako deposits andesitic pyroclastic rocks of the Fukuyama Formation around the Hayakawa deposit Outline of ore deposits A major rhodochrosite veins called the includes a widespread propylitic alteration in addition to hydrothermal alteration responsible Matahachi deposit occur in the Jokoku mine. Fig. 2. Photographs of hand specimens from the Hayakawa deposit: (a) Chalcopyrite-pyrite-tetrane drite-tennantite-galena-sphalerite-bearing quartz veins, (b) Galena -sphalerite-bearing quartz veins. Abbreviations: cp, chalcopyrite; sph, sphalerite; QE, quartz of earlier stage; QL, quartz of later stage; Dol, dolomite. 344 Daizo Ishiyama, Hiroharu Matsueda and Osamu Matsubaya for copper-lead-zinc mineralization at the and quartz with lesser amounts of sphalerite Hayakawa deposit. Alteration minerals in the and galena and rarely enargite, bournonite, propylitic alteration of dacitic pyroclastic semseyite, hessite, tetradymite, aikinite, and rocks consist of quartz, plagioclase, chlorite, apatite. Some grains of apatite are partly sericite, epidote, calcite, and pyrite. Common replaced by quartz. The Pb-Zn quartz veins ly, plagioclase phenocrysts are albitized (M. M. consist of coarse-grained brownish sphalerite, A. J., 1981). Quartz, sericite, and pyrite in coarse-grained subhedral galena, pyrite, and dacitic pyroclastic rocks of the Fukuyama quartz and small amounts of chalcopyrite and Formation