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Hokuriku-Sanin Metallogenic Belt of

Au-Ag Epithermal Vein,

Polymetallic Pb-Zn ± Cu (± Ag, Au)

Vein and Stockwork,

Ag-Sb vein, and

Clastic-Sediment-Hosted U Deposits

(Belt Hok) (Japan)



This Miocene to Pleistocene metallogenic belt is related to veins and replacements in the Japan Cenozoic sedimentary basin that overlies and intrudes the Hiroshima granitic plutonic belt, and the Akiyoshi-Maizuru and Mino-Tamba-Chichibu terranes. The belt occurs in the western part of Honshu and northern Kyushu Islands, trends east-northeast to west-southwest for more than 900 km, and ranges up to 50 km or more wide. The belt occurs in northern most part of the Inner Zone of southwestern Japan and contains Au-Ag epithermal vein deposits (Omori), and polymetallic vein deposits (Taishu). The deposits are associated with siliceous and intermediate magmatism. Tsuboya and others (1956) used the names Toyama, Noto, and Shimane provinces for the Hokuriku-Sanin metallogenic belts. A small number of the Kuroko-type deposits occur in the belt but not described in the mineral deposit database. Ishihara (1978) defined this belt as a Ag-Cu-Pb-Zn province. The belt was originally interpreted as Miocene; however, new K-Ar isotopic ages for the Omori Au-Ag deposit suggest the deposits into the Pleistocene (Sakoda and others, 2000).

Omori Au-Ag Epithermal Vein Mine

This mine (Mining and Materials Processing Institute of Japan, 1994b; Sakoda and others, 2000) consists of seven main northeast striking veins. The Main vein is 400 m long and 0.5 m wide. The veins occur in a area 0.5 km (east-west) by 0.7 km (north-south). The host rocks are Miocene dacite. The ore minerals are argentite, chalcopyrite, pyrite, galena, sphalerite, siderite, and hematite. Gangue minerals are quartz, barite, and chalcedony. Wall rocks are altered to quartz and chlorite. K-Ar sericite age for the alteration zone are 1.07 + 0.04 Ma. A stockwork with disseminated silver ocurs 1 km east of the Main vein. Mining started from 1309 and stopped in 1923. Deposit was also known as the Iwami silver deposit, and was one of the biggest silver mines in Japan. The mine is small with production of 1.4 tonnes Au, 65.7 tonnes Ag, and 6,300 tonnes Cu (from 1891-1919). Average grade is 1,000-2,000 g/t Ag.


Taishu Polymetallic Pb-Zn ± Cu (± Ag, Au) Vein and Stockwork Mine

This mine (Karakida, 1987; Karakida and others, 1992; Ishihara and Imai, 2000) consists of three main north-south and northeast striking vein systems. The Main vein is 2,200 m long and 2 m thick. The host rocks are Paleogene sandstone and shale. The deposit formed during intrusion of a Miocene granitoid that occurs 5 km south. The granitoid consists of fine- to medium-grained monzogranite, granodiorite, and local quartz diorite. The average K-Ar biotite age for the granite is 16.1 + 0.8 Ma. The main ore minerals are sphalerite, galena, pyrrhotite, arsenopyrite, and chalcopyrite. Gangue minerals are calcite and quartz. Wall rocks are altered to chlorite, calcite, sericite, and lesser quartz. The deposit was discovered in 674 and the mine closed in 1973. The mine is medium size with production of 230,000 tonnes Zn, and 139,000 tonnes Pb from 5,000,000 tonnes ore. The average grade is 6.4% Zn, 2.9% Pb.


Origin and Tectonic Controls for Hokuriku-Sanin Metallogenic Belt



The belt is interpreted as forming along an island arc during back-arc rifting or axial part of an island arc that was related to subduction of Philippine Sea Plate. The deposits are associated with siliceous to intermediate magmatism in a back-arc rift or in an island arc.

REFERENCES: Tsuboya and others, 1956; Ishihara, 1978; Sakoda and others, 2000.

Outer Zone Southwest Japan

Metallogenic Belt of Sn Skarn,

Sn-W Greisen, Stockwork, and Quartz

Vein, Polymetallic Pb-Zn  Cu (Ag, Au)

Vein and Stockwork, Au-Ag Epithermal

Vein, Volcanic-Hosted Hg, Ag-Sb Vein,

Zn-Pb (±Ag, Cu, W) Skarn, W-Mo-Be

Greisen, Stockwork, and Quartz Vein,

Hg-Sb-W Vein and Stockwork, Cassiterite-

Sulfide-Silicate Vein and Stockwork, and

Clastic-Sediment-Hosted Sb-Au Deposits

(Belt OSJ) (Japan)



This middle Miocene metallogenic belt is related to veins and replacements in the Japan Cenozoic sedimentary basin that overlies and intrudes the Hiroshima granitic plutonic belt, Sambagawa, Shimanto, and Mino-Tamba-Chichibu terranes. The belt occurs in the outer zone of the Southwestern Japan, trends roughly northeast-southwest for more than 1,000 km, and varies from 50 to 150 km wide. The belt extends further south along the Ryukyu island arc. Most of deposits occur south of Median tectonic line (MTL), but some Hg and Sb deposits occur north of the MTL. The metallogenic belt extend to the east of Itoigawa-Shizuoka tectonic line to the Chichibu deposit.

The deposits are formed during mainly siliceous Miocene magmatism around the igneous bodies. The siliceous igneous rocks are scattered in mainly four areas, the Kii Peninsula (Kumano siliceous igneous rocks) on Honshu Island, the Okueyama-Osuzuyama area on central Kyushu Island, the Osumi Peninsula on southern Kyushu and Yakushima Islands. The siliceous igneous rocks range form 15.5 Ma to 13 Ma. The associated granitoids are mainly ilmenite-series. S-type granitoids occur in the southern part of the belt and I-type granitoids occur in the northern part of the belt. The granitoids are interpreted as occurring along a forearc. The occurrence of siliceous igneous activity in the forearc is unusual. The igneous rock related to the Hg deposit is interpreted as member of Miocene Setouchi volcanic rock that consists of high-Mg andesite. Tsuboya and others (1956) used the name Outer Zone Southwest Japan siliceous igneous rock metallogenic province. Ishihara (1978) used the name Sn-W-Cu-As-Sb province for this metallogenic belt.


Chichibu Zn-Pb (±Ag, Cu, W) Skarn Mine

This mine (Ueno and Shibata, 1986; Ishihara and others, 1987; Mining and Materials Processing Institute of Japan, 1994a) consists of four ore bodies. The ain ore body is 350 m long, 600 m wide, and 40 m thick. The skarn occurs along the margin of a quartz-diorite and averages 30-50 m wide. The ore bodies occur between limestone and skarn. The skarn was formed during intrusion of Miocene quartz-diorite and quartz-diorite porphyry. The granitoids have I-type characteristics. The main ore minerals are native gold, native silver, sphalerite, galena, magnetite, chalcopyrite, pyrite, pyrrhotite, arsenopyrite, and limonite. The gangue minerals are hedenbergite, garnet, epidote, and diopside, quartz, and calcite. Host rocks are Paleozoic limestone and mudstone. K-Ar biotite ages from the quartz-diorite are 5.87 + 0.37 and 6.59 + 0.27 Ma. The aage of ore deposit formation is interpreted as 6.6. The deposit was discovered in 1205 and the mine closed in 1978. The mine is medium size with production of 16.3 tonnes Au, 72 tonnes Ag, 100,000 tonnes Zn, 7,000 tonnes Pb, 440,000 tonnes Fe. Resources of 8,000,000 tonnes.Average grades of 5 g/t Au, 60 g/t Ag, 5.5% Zn, 0.45% Pb, 27.2% Fe.


Kishu Au-Ag Epithermal Vein Mine

This mine (Mining and Metallurgical Institute of Japan, 1968; Mining and Materials Processing Institute of Japan, 1994b) consists of 24 east-west striking vein systems. The veins occur in an area 3 km (east-west) by 5 km (north-south). The Main vein is 1,800 m long and 0.5 m thick. The host rocks are Shimanto Supergroup and Miocene sandstone. The main ore minerals are native gold, argentite, chalcopyrite, pyrite, sphalerite, galena, pyrrhotite, cassiterite, and wolframite. Gangue minerals are mainly quartz, calcite, chlorite, fluorite, sericite, and adularia. Wall rocks are altered mainly to chlorite. The deposit is associated with Miocene Kumano siliceous igneous rocks. The mine is medium size with production of 0.6 tonnes Au, 153 tonnes Ag, and 93,000 tonnes Cu from 9,400,000 tonnes ore. Average grade is 0.2 g/t Au, 26 g/t Ag, 1.4% Cu.


Obira Cassiterite-Sulfide-Silicate Vein and Stockwork Mine

This mine (Mining and Metallurgical Institute of Japan, 1965; Karakida and others, 1992) consists of four main northeast striking veins. The Main vein is 1,400 long and 1.5 m thick. The host rocks are slate of Chichibu Group and Miocene granite porphyry and granite. The deposit formed during intrusion of Miocene granite. The ore minerals are cassiterite, arsenopyrite, pyrite, pyrhotite, and wolframite, molybdenite, chalcopyrite, and sphalerite. Gangue minerals are quartz, tourmaline, and fluorite. The deposit was discovered in 1574. The mine is medium size with production of 800,000 tonnes Sn ore, and 5,000 tonnes Sn. Average grade is 1.2% Sn, 1.56% Cu, and 11.2% As.


Yamatosuigin Hg-Sb-W Vein and Stockwork Mine

This mine (Geological Survey of Japan, 1955; Mining and Metallurgical Institute of Japan, 1968) consists of six northwest striking veins. The Main vein is 400 m long, 0. 5 m wide, and extends 440 m downdip. The host rocks are Cretaceous biotite granite of the Ryoke belt. The ore minerals are cinnabar, native marcury, realgar, and pyrite. Gangue minerals are quartz, chalcedony, sericite, calcite, and adularia. Wall rocks are altered to kaolinite, montmorillonite, and sericite. Deposit formed during Miocene igneous activity. The mine is medium size with production of 645 tonnes Hg grading 0.5% Hg.


Origin and Tectonic Controls for Outer Zone Southwest Japan Metallogenic Belt



The belt is interpreted as forming along an island arc during back-arc rifting or axial part of an island arc that was related to subduction of Philippine Sea Plate.

REFERENCES: Tsuboya and others, 1956; Ishihara, 1978.

Kyushu Metallogenic Belt of

Au-Ag Epithermal Vein Deposits

(Belt Kus) (Japan)



This Pliocene to Quaternary metallogenic belt is related to veins and replacements in the Quaternary Japan volcanic belt and Japan Cenozoic sedimentary basin that overlies and intrudes the Akiyoshi-Maizuru, Shimanto, and Mino-Tamba-Chichibu terranes. The belt occurs in central and southern Kyushu island, trends northeast to southwest for more than 400 km, and ranges from 50 to 100 km wdie. The belt extends further south along the Ryukyu Island arc. The belt contains a large number of Au-Ag epithermal vein deposits (Taio and Hishikari). The Satsuma metallogenic province was defined by Iwasaki (1912) and Watanabe (1923) and is similar to the Kyushu belt. However, the Satsuma province contains Sado and other Au-Ag deposit in other areas of Japan. Tsuboya and others (1956) used the name Kyushu Au-Ag epithermal vein metallogenic province that is similar to the Kyushu metallogenic belt, but excluded sulfur and limonite deposits related to recent volcanoes.

The deposits in the Kyushu metallogenic belt occur mainly in two districts, the Central and Southern Kyushu districts. The Central Kyushu district contains the Taio metallogenic district, and the southern Kyushu district contains the Kushikino metallogenic district of Kinoshita (1961). The Central Kyushu district is closely related to the Beppu-Shimabara graben that trends northeast-southwest, extends for 100 km long, and ranges up to 40 km wide. The Beppu-Shimabara graben is an early Pliocene volcano-tectonic basin. Au-Ag deposits in the area range from 2.7 to 3.5 Ma (MITI, 1999). Although, some Au-Ag epithermal vein deposits are Quaternary, most deposits formed in the Pliocene. Pliocene Au-Ag deposits occur along the northern side of the graben whereas Quaternary deposits occur in the graben (Izawa and Urashima, 1989).

The Southern Kyushu district is subdivided into two areas, the northern Hokusatsu and southern Nansatsu areas., Typical low sulfidation Au-Ag epithermal vein deposits (Hishikari and Kushikino) occur in the Hokusatu area. High sulfidation type epithermal Au deposits occur in the Nansatsu area. The Kushikino deposit in the Hokusatsu area, and high sulfidation type epithermal Au deposits in the Nansatsu area formed in the Pliocene (MITI, 2000a, b). These deposits occur along the western side of the district. The Hishikari, Fuke and other low sulfidation Au-Ag epithermal vein deposits in the Hokusatsu area formed in the Quaternary along the eastern side of the district. Migration of location of deposits from the western backarc side to the eastern volcanic front side occurring with younging (Izawa and Urashima, 1989). Most Au-Ag deposits range from Pliocene to Quaternary in the Southern Kyushu district. Host rock are generally andesitic. However, veins in the deep portion of the Hishikari deposit are occur in the underlying Shimanto Group. The Kyushu metallogenic belt also contains minor sulfur and limonite deposits in Quaternary volcanoes (Kinoshita, 1961). The Kuju sulfur deposit occurs in the Kuju volcano, and the Iojima deposit occurs on the small Iojima Island south of Kyushu Island. Limonite deposits occur in the Aso volcano. However, these deposits are small and not significant and are not listed in the mineral deposit database. The Kagoshima graben, that formed during Quaternary volcanism, occurs in the eastern Southern Kyushu district.

Hishikari Au-Ag Epithermal Vein Deposit

This deposit (Ibaraki and Suzuki, 1993; Naito, 1993; Izawa and others, 1993; Sekine and others, 1998) consists of NE striking veins. Three main vein systems are Honko, Yamada, and Sanjin. Veins occur in an area 2.5 km (EW) by 0.8 km (NS). Veins in Honko range from 1-3 m wide with a maximum strike length of 400 m. Maximum width of the vein is 13 m. Host rock is pre-Miocene Shimanto Supergroup and Quaternary andesite. Ore minerals are electrum, pyrite, chalcopyrite, marcasite, spahlerite, galena, and stibnite. Au/Ag ratio is high, typically about 2. Average grade of Ag is about 100 g/t. Gangue minerals are quartz, adularia, smectite, kaolinite, sericite, chlorite, and calcite. About 20% of gangue is adulaia. Grain size of electrum is about 10 microns. Wallrock show zonal alteration from center to outwards, chlorite-sericite zone, interstratified clay mineral zone, quartz smectite zone, and cristobalite smectite zone. K-Ar isotopic ages of adularia range from 0.78+/-0.07 Ma to 1.05+/-0.07 Ma. Deposit was discovered in 1981. The deposit is medium size with an average grade of 46 g/t Au, and resources of 250 tonnes Au.


Kushikino Au-Ag Epithermal Vein Mine

This mine (Shiga and Urashima, 1988; Karakida and others, 1992) consists of northeast striking veins. The Main vein is 2,600 m long and ranges from 3 to 50 m wide. The veins occur in a area 3 km (east-west) by 2.5 km (north-south). The host rocks are Miocene andesite and andesite tuff. The ore minerals are electrum, native silver, argentite, pyrargyrite, stibnite, naumannite, hessite, and stephanite. Gangue minerals are quartz, adularia, sericite, and calcite. Wall rocks are altered to quartz, pyrite, chlorite, calcite, sericite, and kaolinite. A K-Ar isotopic age is 4.0 + 0.3 Ma. Mining started in the Seventeenth century. The mine is medium size with production of 54.7 tonnes Au and 497 tonnes Ag from 8,270,000 tonnes ore. Average grade is 6.6 g/t Au, 60 g/t Ag.


Taio Au-Ag Epithermal Vein Mine

This mine (Mining and Materials Processing Institute of Japan, 1989; Karakida and others, 1992) consists of two main vein systems that strike east-northeast and northwest and dip north. The veins occur in an area 3 km (east-west) by 2 km (north-south). The Main vein is 1,750 m long and 2.5 m thick Host rocks are altered Miocene andesite. The main ore minerals are native gold, argentite, miargyrite, chalcopyrite, pyrite, galena, and sphalerite. Gangue minerals are mainly quartz, calcite, adularia, and rhodonite. Wall rocks are altered to quartz, chlorite, sericite, montmorillonite, and kaolinite. A K-Ar adularia age for the vein is 3.6 Ma. The deposit was discovered in 1894. The mine closed in 1970. The mine is medium size with production of 37 tonnes Au and 160 tonnes Ag from 5,870,000 tonnes ore. Average grade is 6.3 g/t Au, 27 g/t Ag.


Origin and Tectonic Controls for Kyushu Metallogenic Belt



This belt is interpreted as forming during hydrothermal activitiy along a Pliocene and Quaternary island arc during back-arc rifting or the axial part of an island arc that was related to subduction of Philippine Sea Plate.

REFERENCES: Iwasaki, 1912; Nishiwaki and Watanabe, 1956; Watanabe, 1923; Kinoshita, 1961; Tsuboya and others, 1989; MITI, 2000a, b.

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