Copper-Lead-Zinc Mineralization at the Hayakawa and Shakako Deposits 343

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 are regarded as alteration products tetrahedrite. Ferromanganoan dolomite related to the copper-lead-zinc mineralization occurs as a drusy mineral in the central part of (Sawa et al., 1965). Pb-Zn quartz veins (Ishiyama and Matsueda, Mineralization stages and mineral paragenesis 1986). There are two kinds of veins, chalcopyrite- Cu-Pb-Zn quartz veins in the Shakako pyrite-tetrahedrite-galena-sphalerite-bearing deposit include large amounts of pyrite, chal quartz veins (hereafter abbreviated as Cu-Pb- copyrite, tetrahedrite-tennantite, and quartz Zn quartz veins) and galena-sphalerite-bearing with lesser amounts of sphalerite and galena quartz veins (hereafter abbreviated as Pb-Zn and small amounts of kesterite, arsenosulvanite quartz veins) at the Hayakawa deposit (Fig. 2). and Cu-Fe-Zn-Sn-S mineral. Mineral par The Cu-Pb-Zn quartz veins are partly cut by agenesis of Cu-Pb-Zn quartz veins of the Sha the Pb-Zn quartz veins. Major constituent kako deposit is almost identical to that of the minerals of the Cu-Pb-Zn quartz veins are Hayakawa deposit. Pb-Zn quartz veins in the chalcopyrite, pyrite, tetrahedrite-tennantite, Shakako deposit consist of large amount of

Fig. 3. Paragenetic sequence of copper-lead-zinc mineralization at the H acakawa and Shakako d eposits. Copper-lead-zinc mineralization at the Hayakawa and Shakako deposits 345

quartz with small amounts of galena, sphaler

ite, pyrite and electrum.

Mineralization at the Hayakawa and Sha

kako deposits is divided into two stages as

shown in Fig. 3. The earlier stage consists of

Cu-Pb-Zn quartz veins, while the later stage

consists of Pb-Zn quartz veins. Bournonite,

semseyite, hessite, tetradymite, aikinite, kester

ite, arsenosulvanite, Cu-Fe-Zn-Sn-S mineral,

and apatite are found only in the earlier stage

veins.

Mode of occurrence and chemical composi

tions of ore minerals

This section describes mode of occurrence

and chemical composition of sphalerite, silver

bearing minerals, and some rare ore minerals.

Chemical analyses of ore minerals were made

by JXA-5 type electron probe microanalyzer.

Operation conditions and correction of relative Fig. 4. Histogram (Frequency N: number of anal intensity for quantitative analyses are the same ysis) showing FeS content in sphalerites as in Ishiyama and Matsueda (1988). coexisting with pyrite from chalcopyrite-

Sphalerite: Sphalerite in both the earlier and pyrite-tetrahedrite-galena-sphalerite- bearing quartz veins (earlier stage) and later stages occurs as allotriomorphic granular galena-sphalerite-bearing quartz veins aggregates. Grain size of sphalerite (0.5mm to (later stage) at the Hayakawa deposit.

1ƒÊm in diameter) in the earlier stage is distinct

ly smaller than that of sphalerite (1cm to 0.1 Tetrahedrite-Tennantite: Tetrahedrite-ten-

mm in diameter) in the later stage. Sphalerite nantite occurs as irregular grain forms, and

in the earlier stage shows intergrowths with mainly intergrows with pyrite, sphalerite, and

pyrite, chalcopyrite, galena, tetrahedrite-ten- chalcopyrite. It contains minute and irregular nantite, enargite, bournonite, semseyite, hes inclusions of sphalerite and chalcopyrite. The

site, aikinite, tetradymite, kesterite, ar ranges of Sb and As contents in these minerals

senosulvanite, an unidentified Cu-Fe-Zn-Sn-S are from 3.7 to 14.5 atom% and from 11.3 to 0

mineral, quartz, and apatite. Sphalerite con .0 atom%, respectively (Table 1, Fig. 6 in

tains small (10ƒÊm to 1ƒÊm in diameter) inclu Ishiyama and Matsueda, 1988). Ag, Bi, and Te

sions of chalcopyrite which are sometimes contents in tetrahedrite-tennantite do not

orientated. Sphalerite of the later stage shows exceed 3.7 atom%, 0.4 atom% and 0.1 atom%,

intergrowths with pyrite, chalcopyrite, galena, respectively (Table 1). Distinct heterogeneity

tetrahedrite, electrum, and quartz and Bi, Te, in Sb and As contents is commonly observed

Sn and V-bearing ore minerals are absent. within single grains of tetrahedrite-tennantite

FeS content in sphalerite decreases from earlier (Fig. 5).

(8.8-1.8 mol%) to later stages (2.2-0.3 mol%), as Enargite: Enargite occurs as allotriomorphic

shown in Fig . 4. or subhedral grains of 3ƒÊm to 70ƒÊm in diame 346 Daizo Ishiyama, Hiroharu Matsueda and Osamu Matsubaya

Table 1. Chemical composition of tetrahedrite-tennantite from the Hayakawa (Nos. 1 to 11) and Shakako (Nos. 12 to 14) deposits

1 & 2, tetrahedrite which occurs as intergrowth with aikinite; 3, tetrahedrite (rim); 4, tetrahedrite ( 14core); 5-9, tetrahedrite; 10, tennantite (rim); 11, tennantite (core); 12 & 13, tetrahedrite; , tennantite.

Fig. 5. (a) Photomicrograph of tetrahedrite (tet) coexisti ng with sphalerite (sph), chalcopyrite (cp) and quartz (Q), (b) Back-scattered electron image showing compositional het erogeneity of tetrahedrite , (c) Characteristic X-ray image of Sb Lƒ¿ , (d) Characteristic X-ray image of As Lƒ¿ . Copper-lead-zinc mineralization at the Hayakawa and Shakako deposits 347

Table 2. Chemical composition of enargite , arsenosulvanite, the unidentified Cu-Fe-Zn-Sn-S mineral , kesterite, and, electrum from the Hayakawa and Shakako deposits

1-5, enargite (Hayakawa deposit); 6, arsenosulvanite (the Hayakawa deposit); 7, Cu-Fe-Zn-Sn-S mineral (the Shakako deposit); 8, kesterite (the Shakako deposit); 9 & 10, electrum (the Shakako deposit).

ter. Twinning is not present under a micro respectively (Table 2).

scope. Enargite forms intergrowths with Cu-Fe-Zn-Sn-S mineral: An unidentified Cu-

pyrite, chalcopyrite, sphalerite and tennantite. Fe-Zn-Sn-S mineral occurs as grains inter

Assuming that the total number of atoms is 8, grown with chalcopyrite and kesterite in ten the empirical formula is: Cu2.94-3.04(As0.92-0.96 nantite and sphalerite. Size of this mineral is

Sb0.00-0.04Fe0.02-0.16)1.01-1.14S3.93-3.96. Maximum about 25•~15ƒÊm, and microscopically its color

Sb and Fe contents are 0.5 atom% and 2.0 (in oil) is dull orange. Bireflectance and atom%, respectively (Table 2). The enargite anisotropy (in oil) are distinct, and internal

composition is close to the Cu3AsS4 end-mem reflections are not present. Its optical prop

ber. erties are similar to stannite in the list of

Arsenosulvanite: Arsenosulvanite occurs as Uytenbogaardt and Burke (1971). This min

polygonal inclusions (20•~10ƒÊm) in pyrite. eral is slightly rich in Cu (3.9 atom%) and poor Microscopically, the color of arsenosulvanite in Sn (3.6 atom%) as compared with stoi

(in air) is light pinkish brown. Bireflectance, chiometric stannite. The mineral is poorer in anisotropy, and internal reflections were not Cu (5.7 atom%) and richer in Fe+Zn, Sn, and S recognized under the microscope. Assuming (2.6, 1.0 and 2.1 atom%, respectively) than stoi- that the total number of atoms is 8, the result chiometric stannoidite (Table 2). This mineral

ing empirical formula would be: Cu2 .88(As0.54 is classified as Sn-sulfosalts such as stannite,

V0.24Fe0. 24Sb0 .13Sn0.03)1.16S3.94. The Cu: (As+ mohite and kuramite, and has a metal to sulfur V+Fe+Sb+Sn): S atomic ratio is approxi ratio of approximately one. Considering the mately 3:1:4. Contents of As and V in ar metal to sulfur ratio and charge balance senosulvanite are about 7 atom% and 3 atom%, between metal and sulfur, the resulting empiri 348 Daizo Ishiyama, Hiroharu Matsueda and Osamu Matsubaya

cal formula is: Cu6.00(Zn1.55Cu0.29Fe2+0.11Sn2 .15 (Sb1.99As0.02)2.01S6.04(Table 3). It is poor in Pb

Fe3+1.84)5.95S12 .03. The chemical formula resem compared with stoichiometric bournonite. bles zincian ferrian mohite. Semseyite: Semseyite forms aggregates of Kesterite: Kesterite forms allotriomorphic short prismatic grains enclosed in tetrahedrite. granular aggregates. Its size is from 40•~20 Color of semseyite under the microscope(in air) ƒÊ m to 20•~10ƒÊm. Kesterite, together with is white with a greenish tint. Bireflectanceand chalcopyrite and the Cu-Fe-Zn-Sn-S mineral, anisotropy are strong. Internal reflectionsare occur in intimate intergrowths with tennantite not recognized. Its optical properties are simi and sphalerite. Color of kesterite under the lar to those listed in Uytenbogaardt and Burke microscope (in oil) is aluminum gray, and (1971). Assuming that the total number of bireflectance, anisotropy and internal atoms is 38, the empirical formula is Pb8.85-8.93 reflections (in oil) are not recognized. The (Sb8.21-8.13As0.04)8.25-8.17S20.90(Table 3). This empirical formula is Cu1 .98(Zn0.77Fe0.33)1.10Sn0.90 mineral is assumed to be semseyite on the basis S4.02(Table 2). In contrast, kesterite in Cu-Pb- of its optical properties and crystal forms de Zn quartz vein at the Shakako deposit is slight scribed by Uytenbogaardt and Burke (1971), ly rich in Zn+Fe (1.3 atom%) and poor in Sn although its chemical composition from the (1.3 atom%). Hayakawa deposit is poor in Pb compared with Bournonite: Bournonite occurs usually as ir stoichiometric semseyite, and it is intermediate regular grains. The grains intergrow with in composition between semseyite and galena, sphalerite, tetrahedrite, and hessite. madocite. Bournonite also occurs as inclusions in tetrahe Hessite: Allotriomorphic crystals of hessite drite. Its optical properties are similar to show intimate intergrowths with tetrahedrite, those listed in Uytenbogaardt and Burke (1971) . chalcopyrite, galena, and bournonite. Assuming Assuming that the total number of atoms is 12, that the total number of atoms is 3, the empiri the empirical formula is Pb1 .79(Cu2.12Ag0.04)2.16 cal formula is Ag1.97-1.96(Te1.08-1.04Sb0.01)1.04-1.05

Table 3. Chemical composition of bournonite , semseyite, hessite, tetradymite, aikinite, and galena from the Hayakawa deposit

1, bournonite; 2 & 3, semseyite; 4 & 5 , hessite; 6, tetradymite; 7 & 8, aikinite; 9 & 10, galena which occurs as intergrowth with aiki nite. Copper-lead-zinc mineralization at the Hayakawa and Shakako deposits 349

(Table 3). The composition of hessite from the Oxygen isotopic ratios of vein quartz and wall Hayakawa deposit is close to stoichiometric rocks hessite. In order to estimate the origin of ore fluid Tetradymite: Tetradymite occurs as subhe responsible for copper-lead-zinc mineralization dral and irregular grains. Its size is about 13ƒÊ of the Hayakawa and Shakako deposits, a total m. Tetradymite forms as intergrowths with of 9 samples was prepared for oxygen isotope galena, chalcopyrite, and tetrahedrite-ten analyses by F2 technique (Kita and Matsubaya, nantite. Color of tetradymite under the micro 1983). Pure quartz samples were handpicked scope (in air) is white with a creamy yellow tint. for analyses. However, some of fine grained Bireflectance and anisotropy are weak. Inter samples intergrown with sulfide minerals were nal reflections are not present. Assuming that

the total number of atoms is 5, the empirical pretreated with a hot mixture of bromine and nitric acid. The oxygen standard is Standard formula is Bi2.00Te1.99S1.01 (Table 3). Tetra Mean Ocean Water (SMOW). Repro dymite in Cu-Pb-Zn quartz veins at the Haya ducibilities of measurements are mostly kawa deposit is stoichiometric tetradymite. within•}0.1 per mil. Aikinite: Aikinite occurs as prismatic and ir ƒÂ18O values of several quartz grains from regular crystals. Its size is from 150•~25ƒÊm to

25•~25ƒÊm. Aikinite intergrows with galena, the Hayakawa and Shakako deposits are shown in Table 4.ƒÂ18O values of quartz in Cu- tetrahedrite-tennantite, and chalcopyrite.

Color of aikinite under the microscope (in air) is Pb-Zn and Pb-Zn quartz veins from the Haya

white with a light tint of cream. Bireflectance kawa deposit range from 1.4 to 3.1 per mil. In

and anisotropy are strong. Internal reflections contrast, the ƒÂ18O value of quartz in Cu-Pb-Zn

are not recognized. Assuming that the total quartz veins from the Shakako deposit is 1.9

number of atoms is 12, the empirical formula is per mil, which is within the range of ƒÂ18O values

Pb1.93Cu1.92-1.94Bi2.61-2.24S5.90-5.76. The composi for vein quartz at the Hayakawa deposit. The ƒÂ18O value for quartz in veinlets associated tion of aikinite from the Hayakawa deposit is

slightly rich in Bi. The galena intergrown with fine-grained molybdenite, pyrite, fluorite

with aikinite contains the largest amounts of and sericite (55MADO-1, 233.2m) is 3.4 per mil

Ag and Bi (1.8 atom% and 4.3 atom%, respec (Ishihara and Morishita, 1983), which is similar

tively, Table 3). to the values for vein quartz from the Haya

Electrum: Electrum from the Shakako deposit kawa deposit. ƒÂ18O values of propylitically altered an occurs commonly as irregular grains (50•~30

ƒÊm in size) enclosed in quartz. Au content desite pyroclastic rocks of the Middle Member

determined by EPMA analysis varies from 41.9 of the Fukuyama Formation are 6.1 and 6.3 per

to 49.4 atom% (Table 2). Au content in mil (Table 4). Whereas, ƒÂ18O values of hydro

electrum from Pb-Zn quartz veins at the Sha- thermally altered dacitic pyroclastic rocks for

kako deposit is within the range of the Au ming the wall rocks of the Hayakawa and

content in electrum from Pb-Zn-(Mn) quartz Shakako deposits, are 0.8 and 1.5 per mil,

veins at the Matahachi deposit of the Jokoku respectively (Table 4). These values are lower

mine. than those of propylitically altered pyroclastic rocks of the Middle Member of the Fukuyama

Formation. 350 Daizo Ishiyama, Hiroharu Matsueda and Osamu Matsubaya

Table 4. ƒÂ18O values for quartz and wall rocks, and those of ore fluids responsible for the Hayakawa and Shakako deposits

, after Ishiyama et al. (1987); **, after M. M. A. J. (1981); *** , after Ishihara and M orishita (1983).ƒÂ1

8O values of ore fluids are calculated using fractionation factor of quartz -water by Matsuhisa et al . (1979).

The Cu-Pb-Zn quartz veins include enargite, Discussion tetrahedrite-tennantite, tetradymite, aikinite, Comparison with molybdenite-bearing base arsenosulvanite, kesterite, bournonite, sem metal and manganese-lead-zinc mineralization seyite, and hessite. Fluorite occurs in some Copper-lead-zinc mineralization at the quartz veins at the Hayakawa deposit and in Hayakawa and Shakako deposits is compared some molybdenite-bearing quartz veinlets. with molybdenum-bearing base metal mineral Further, the mineral assemblages of the ization in a nearby borehole (55MADO-1) . Cu-Pb-Zn quartz veins at the Hayakawa and This mineralization is also compared to manga Shakako deposits and veinlets in the borehole nese-lead-zinc mineralization at the Matahachi differ distinctly from the mineral assemblage of deposit of the Jokoku mine. rhodochrosite veins at the Matahachi deposit; Pyrite, galena, sphalerite, and quartz occur Galena-sphalerite-bearing rhodochrosite veins in both Cu-Pb-Zn quartz veins at the Haya and rhodochrosite veins at the Matahachi kawa and Shakako deposits and molybdenite deposit include pyrargyrite, polybasite, freiber bearing quartz veinlets from a nearby drill hole . gite, argyrodite and argentite in addition to

* Copper-lead-zinc mineralization at the Hayakawa and Shakako deposits 351

rhodochrosite veins and rhodochrosite veins at sphalerite, galena, pyrite, chalcopyrite and rhodochrosite (Ishiyama et at., 1987). the Matahachi deposit (Ishiyama et al., 1987). Tetradymite, aikinite, arsenosulvanite, kester The potassium-argon age for the forma ite and molybdenite, which are found at the tion of molybdenite-bearing quartz veinlets 0.5 Hayakawa and Shakako deposits and in the kilometers south of the Katsuraoka deposit is veinlets, tend to be associated with polymetallic 14.0 Ma, while those of Neogene intrusive rocks vein deposits and skarn deposits related to in the Jokoku-Katsuraoka mining area range igneous rocks rather than with epithermal vein from 17.7 to 14.0 Ma (M. M. A. J., 1981). These deposits, such as the Matahachi deposit. potassium-argon age data suggest that molyb

Homogenization temperatures of fluid denum-bearing base metal mineralization in

inclusion for Cu-Pb-Zn quartz veins and Pb-Zn the Jokoku-Katsuraoka mining area is closely associated with Neogene intrusive activities. quartz veins at the Hayakawa deposit range from 202•‹to 313•‹and 196•‹to 264•Ž, respective Judging from mineral assemblages, esti

ly (Ishiyama et al., 1987). Formation tempera mated environments of ore formation, potas

tures of ores at the Hayakawa deposit decrease sium-argon age data and spatial relationships

from the earlier to later stages. Considering between the Hayakawa and Shakako deposits and molybdenite-bearing quartz veinlets from the mineral assemblage tennantite-enargite-

sphalerite-pyrite and chemical composition of the nearby borehole, the Cu-Pb-Zn quartz veins

sphalerite (1.7 to 5.0 mol.% FeS) coexisting at the Hayakawa and Shakako deposits and the

with pyrite, roughly estimated temperatures veinlets are considered to be related to Neogene intrusive rocks which serve as sources and sulfur fugacities for the mineralization of of heat and metals such as molybdenum. Con Cu-Pb-Zn quartz veins at the Hayakawa

deposit range from 250•‹to 400•Ž and 10-9.6 to sidering geological data and estimated mineral

10-5.4 atm, respectively (Ishiyama et al., 1987). ization environments presented above, Cu-Pb-

These temperatures are slightly higher than the Zn quartz veins of the two deposits are inferred

homogenization temperature. Homogeniza to have been formed under a subvolcanic condi

tion temperatures of fluid inclusions of molyb tion (Schneiderhohn, 1949, 1955).

denite-bearing quartz veinlets in the borehole Origin of ore fluid inferred from ƒÂ18O values of

range from 256•‹to 292•Ž with a mean of 277•Ž quartz Oxygen isotopic compositions for ore fluid (M. M. A. J., 1981), and falls within those for Cu- Pb-Zn quartz veins at the Hayakawa deposit. responsible for Cu-Pb-Zn quartz veins can be

Therefore, we assume that formation tempera calculated using the ƒÂ18O values for quartz, the

tures of Cu-Pb-Zn quartz veins at the Haya formation temperature inferred from fluid

kawa deposit are within the same range as inclusion data (Ishiyama et al., 1987), and the

those for molybdenite-bearing quartz veinlets fractionation factor of quartz-water by Matsu

in the borehole. Whereas, homogenization tem hisa et al. (1979). The calculated 618OH2O val

peratures for galena-sphalerite-bearing rhodo ues range from -10.1 to -3.3 per mil for the

chrosite vein at the Matahachi deposit are from fluids related to Cu-Pb-Zn and Pb-Zn quartz

129•‹to 293•Ž with a mean of about 195•Ž. veins of the Hayakawa deposit (Table 4), while

Thus homogenization temperatures for Cu-Pb- calculated ƒÂ18OH2O values for molybdenite-bear

Zn quartz veins at the Hayakawa and Shakako ing quartz veinlets is -4.3 per mil (Ishihara and

deposits and the veinlets from the borehole, are Morishita, 1983). The calculatedƒÂ18O values

higher than those for galena-sphalerite-bearing of ore fluids for the Hayakawa deposit are 352 Daizo Ishiyama, Hiroharu Matsueda and Osamu Matsubaya relatively low compared with sea water (0 per field work. Dr. I. Kita of Akita University has mil; Sheppard, 1986) and primary magmatic provided technical assistance and laboratory water (5.5 to 9.5 per mil Sheppard, 1986). facilities for isotopic analysis, which is greatly

Both calculated ƒÂ18OH2O values suggest that the appreciated. The authors thank Dr. A. Kato of ore fluids responsible for formation of the Cu- National Science Museum for his helpful com

Pb-Zn quartz veins and molybdenite bearing ments on Cu-Fe-Zn-Sn-S mineral. The quartz veinlets are dominantly meteoric water authors also would like to acknowledge the origin. This interpretation agrees with the continuing guidance and encouragement of Mr. fact that the salinity of fluid inclusions in Cu- K. Kurosawa of the Geological Survey of Hok

Pb-Zn quartz veins of the Hayakawa deposit is kaido, Prof. Y. Ishikawa of Akita University considerably low (0.2-4.2 wt% NaCl eq.; Ishi and Prof. Emeritus, T. Nakamura of Osaka yama et al., 1987). City University. Dr. R. E. Derkey of the Wa shington State Department of Natural Conclusions Resources is also gratefully acknowledged for

We conclude that Cu-Pb-Zn quartz veins critically reviewing the earlier manuscript. at the Hayakawa and Shakako deposits formed The expense of this research was partially at relatively shallow depths, while molyb supported by the Arai Science and Technology denite-bearing quartz veinlets formed at Foundation to DI and Grants-in-Aid for greater depths, spatially closer to Neogene Scientific Research from the Ministry of Educa intrusive rocks occurring in the east part of the tion of Japan No. 63470043 to HM and No. Hayakawa deposit. All these vein deposits 01460060 to Prof. T. Maruyama of Akita Uni appear to be related to the Neogene intrusive versity. rocks, which are assumed to serve as sources of heat and metals such as molybdenum. The References Cu-Pb-Zn quartz veins and molybdenite bear ing-quartz veinlets were formed from ore fluids Bamba, T. (1957),Cu-Pb-Zn-Mn deposits in the vicinity of middle stream of Ishizaki-river, of meteoric water origin in a subvolcanic envi Kaminokuni-mura, Hiyama-gun, Hokkaido. ronment. These conclusions are based upon HokkaidoChikashigen Chosa-shiryo, No. 30,3- the above spatial relationships between the 16 (in Japanese). Enjoji, M. and Takenouchi, S. (1976),Present and intrusive rocks and the vein deposits, potas future researches of fluid inclusionsfrom vein sium-argon age data of Neogene intrusive type deposits. Soc. Mining Geol.Japan, Spec. rocks and molybdenum-bearing base metal Issue, 7, 87-100 (in Japanese with English mineralization, mineral assemblages, homogen abstract). Ishiga, H. and Ishiyama, D. (1987),Jurassic ac ization temperatures, and calculated ƒÂ18OH2O cretionary complex in Kaminokuni terrane, values for ore fluids in equilibrium with vein southwestern Hokkaido, Japan. Mining quartz. Geol.,37, 381-394. Ishihara, S. and Morishita, Y. (1983),Neogene molybdenite mineralization in the Jokoku Acknowledgements: The authors wish to mine area, Hokkaido. Bull. Geol. Surv express their sincere thanks and gratitude to Japan, 34, 81-87 (in Japanese with English Mrs. N. Hoashi and E. Kato of the Chugai abstract).

Mining Co., LTD. and Mr. K. Adachi of the Ishiyama, D, and Matsueda, H. (1986),Mode of occurrences and chemical compositions of Mitsui Mineral Development Engineering Co ., dolomite and kutnahorite related to manga LTD. for rendering support during the course of nese mineralizationat the Jokoku mine,south Copper-lead-zinc mineralization at the Hayakawa and Shakako deposits 353

western Hokkaido, Japan. J. Japan. Assoc. Ministry of International Trade and Industry , Min. Petr. Econ. Geol., 81, 205-217 (in 82p. (in Japanese). Japanese with English abstract). Narita, E. (1961), Molybdenite in diorite porphyrite Ishiyama, D., Matsueda, H. and Nakamura, T. at the southern part of the Katsuraoka iron (1989), Polymetallic-mineralizations in the deposit, Hiyama-gun, Hokkaido. Hokkaido Jokoku-Katsuraoka mining area, southwest Chishitsu-Yohou, No. 40, 37-39 (in Japanese) . ern Hokkaido, Japan. Mining Geol., 37, 1-14 Sawa, T., Yamaya, M., Murase , T. and Ikeda, K. (in Japanese with English abstract). (1965), Cu, Pb, Zn and Mn deposits of Haya Ishiyama, D. and Matsueda, H. (1988), Modes of kawa area, Kaminokuni-mura, Hiyama-gun. occurrence and chemical compositions of sil Hokkaido Chikashigen chosa-shiryo , No. 96, 1- ver-bearing minerals and accompanied min 33 (in Japanese). erals from the Matahachi deposit of the Joko Schneiderhohn, H. (1949), Erzlagerstatten. 2. Aufl . ku mine, southwestern Hokkaido. Rep. Res. Piscator, Stuttgart, 326p. Inst. Nat. Resour. Min. Coll. Akita Univ., No. Schneiderhohn, H. (1955), Erzlagerstatten. 3. Aufl. 53, 17-32 (in Japanese with English abstract). VEB Gustav Fischer, Jena, 375p. Kita, I. and Matsubaya, O. (1983),F2 technique for Sheppard, S. M.F. (1986), Characterization and the oxygen isotopic analysis of silica minerals. isotopic variations in natural waters. In Sta Rep. Res. Inst. Underground Resources, Min. ble Isotopes in High Temperature Geological Coll. Akita Univ., No. 48, 25-33. Processes (Valley, J. W., Taylor, H. P., Jr. and Matsuhisa, Y., Goldsmith, J. R. and Clayton, R.N. O'Neil, J. R. Eds.). Mineralogical Society of (1979),Oxygen isotopic fractionation in the America, Reviews in Mineralogy, 16, 165-183. system quartz-albite-anorthite-water. Geo Uytenbogaardt, W. and Burke, E. A. J. (1971), chim. Cosmochim. Acta, 43, 1131-1140. Tables for the microscopic identification of Metal Mining Agency of Japan (1981), Reports on ore minerals. 2nd rev. ed., Elsevier Pub. Co., the regional geology of the Kudo district. Amsterdam, 430p.

西南北海道上国-桂岡鉱床地域早川・釈迦坑鉱床の銅鉛亜鉛鉱化作用

石山大三・松枝大治・松葉谷治

早期鉱床と釈迦坑鉱床の銅鉛亜鉛鉱化作用の特徴が,単位鉱脈の構造・鉱物組合せ・鉱化ステージそして鉱脈中の石英および母岩の酸素同位体組成に基つきまとめられている。早川および釈迦坑鉱床には,黄銅鉱-黄鉄鉱-四面安銅鉱-方船鉱-閃亜鉛鉱を随伴する石英脈(銅鉛亜鉛石英脈)と方鉛鉱-閃亜鉛鉱を随伴する石英脈(鉛亜鉛石英脈)が存在する。銅鉛亜鉛石英脈は,鉛亜鉛石英脈より早期に形成された。銅鉛亜鉛石英脈の鉱物組合せは,黄銅鉱,黄鉄鉱四面安銅鉱-西面砒銅鉱,方鉛鉱,閃亜鉛鉱,硫砒銅鉱,車骨鉱,セムセイ鉱,ヘッス鉱,黄錫亜鉛鉱,砒サルバン,鉱Cu- Fe-Zn-Sn-S系鉱物,硫テルル蒼鉛鉱,アイキン鉱,石英および燐灰石である。鉛亜鉛石英脈の鉱物組合せは,方船鉱,閃亜鉛鉱,黄鉄鉱,黄銅鉱,四面安銅鉱,エレクトラムおよび石英である。閃亜鉛鉱中のFeS

含有量は,早期から晩期の鉱化作用にかけて減少する。四面安銅鉱-四面砒銅鉱の単-粒子内では, Sbと Asの間に化学組成の顕著な不均質性が認められる。

早川鉱床の銅鉛亜鉛石英脈中の石英のδ18O値は, 1.4～3.1パーミルの範囲を有する。一方,釈迦坑鉱床の銅鉛亜鉛石英脈中の石英のδ18O値は, 1.9パーミルである。早川鉱床の生成に関与した熱水のびδ18O値 (-10.1～-3.3パーミル)は,海水やマグマ水のδ18O値と比較すると相対的に低い。従って,早川および釈迦坑鉱床の銅鉛亜鉛石英脈は, subvolcanic環境下でしかも天水起源の熱水から形成されたと推定される。