By Sergey M. Rodionov1, Alexander A. Obolenskiy2
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Koksung Metallogenic Belt ofMetamorphic Graphite Deposits(Belt KO) (South Korea)This Mesoproterozoic and Neoproterozoic metallogenic belt is hosted in Yeongnam Metamorphic Complex (part of Sino-Korean Craton, Yeongnam granulite-paragneiss terrane) and Jurassic Daebu granite belt. The major deposit is at Koksung. The age of the belt ranges from 1400 to 800 Ma. The Yeongnam terrane consists of leucogranite gneiss, hornblende plagioclase gneiss, biotite gneiss and biotite schist. Koksung Graphite DepositThis deposit (Lee, 1960) occurs at Songjongni, Ogok-myeon, Koksung-gun, Chollanam-do province and is an undeveloped, newly-discovered graphite occurence. Host rocks chiefly consist of granite gneiss, biotite schist with variable graphite content, and graphite-biotite schist with small amount of graphite. In the biotite schist zone are six ore shoots with relatively good content of graphite that is lenticular and extremely irregular. The deposit is small with an average grade of 5.46% F.C. and reserves of 6,770 tonnes. Origin and Tectonic Controls forKoksung Metallogenic BeltThe belt is hosted in Yeongnam Metamorphic Complex that consists of leucogranite gneiss, hornblende plagioclase gneiss, biotite gneiss, and biotite schist. Graphite deposits occur in granite gneiss and graphite bearing biotite schist generally minor graphite. REFERENCES: Lee, 1962; Duk Hwan Hwang, this study. NEOPROTEROZOICMETALLOGENIC BELTS(1000 to 540 Ma)Igarsk Metallogenic Belt ofSediment-Hosted Cu Deposits(Belt IG) (Western margin of North SiberianCraton, Russia)This Vendian to Early Cambrian metallogenic belt occurs in the northwestern North Asian Craton Margin and consists of lenses of red-bed sedimentary rocks that occur in a Vendian submontane basin in the Riphean Igarsk uplift (Dyuzhikov and others, 1988). The belt occurs in a sublongitudinal, narrow band up to 100 km long. The host late Riphean and Early Cambrian sedimentary rocks occur in three structural levels: (1) intensely deformed clastic and carbonate rock of the Ludovsk and Gubinsk Series (early and middle Riphean); (2) clastic and carbonate deposits of the Chernorechensk Series, and red-bed clastic rocks of the Izluchinsk Series (late Riphean); and (3) carbonate rock with rare sandstone and siltstone of the Vendian and Early Cambrian Sukharinsk Series. There are two persistent horizons of Cu deposits. The lower horizon occurs in a transitional zone between the Izluchinsk red-bed suite and the underlying grey sedimentary rock of the Chernorechensk suite. This horizon is about 5 m thick (rarely up to 15 meters) and consists of of fine-grained disseminated digenite, bornite, and chalcopyrite. The upper horizon occurs at the base of marine grey deposits of the Sukharinsk suite and overlying red-beds of the Izluchinsk suite. The horizon is 10 to 30 m thick. Cu-rich areas often occur in the upper ore horizon (Graviiskoye and Sukharinskoye deposits). Two types of deposits are distinguished, deposits directly connected with host strata and crosscutting high-grade deposits in fracture zones. The major deposit is at Graviiskoye. Graviiskoye Sediment-Hosted Cu DepositThis deposit (Rzhevskiy and others, 1980; Gablina and others, 1986; Djuzhikov and others, 1988; Lurie, 1988) is hosted in late Riphean red and grey sedimentary rock consisting of alternating argillite, clay limestone, and marl). Southern, northern, central, and eastern deposits are recognized. The Southern and Northern deposits occur in basal layers of lagoon sedimentary rock. The Southern deposit is 3.3 km long, and the Northern deposit is 1 km, and both fary from a few meters to 60 m thick. Sulfide minerals occur in streaks. Main ore minerals are diagenite, bornite, chalcopyrite, and pyrite. Slight silica alteration of wall rocks occurs. The Central deposit occurs above a paleouplift between two reefs. The deposit is 900 m long and up to 70 m thick. Main ore minerals are djurleite and bornite that occur in lenses and streaks. Sparse chalcopyrite and galena occur at the deposit periphery. Wall-rock alteration consists mainly of intense silica alteration with widespread antraxolite. The Eastern deposit consists of numerous lenses and ore-bunches of Cu minerals in conglomerate and breccias in the reef shelf. Main ore minerals are digenite and bornite with rare chalcopyrite, galena, and pyrite. Wall-rock alteration consists of carbonate minerals, and sparse antraxolite. The deposit is small. Origin and Tectonic Controls for Igarsk Metallogenic BeltThe belt forms the northern large margin of the Pribaikal-Yeniseisk Cu belt (Malich and others, 1987). The late Precambrian deposits of Cu sandstone and Cu slate in the Igarsk uplift. The Cu-bearing rocks coincides with the late Riphean Norilsk-Turukhansk aulacogen. Cu deposits are related to the zones of lateral pinching of red-bed molasse sedimentary rock that formed in the final stage of development of orogen basin (Malich and Tuganova, 1980). Cu minerals were deposited in a katagenesis environment during migration of groundwater. Metals precipitated along the hydrosulfuric geochemical barriers. Deposits are interpreted as forming along flexures, anticline uplifts, and fracture zones that were favorable to migration of Cu-bearing groudwaters (Lurie, 1988). REFERENCES: Malich, Tuganova, 1980; Malich and others, 1987; Djuzhikov and others, 1988; Lurie, 1988. Isakovsk Metallogenic Belt ofVolcanogenic-Sedimentary Mn andVolcanogenic Cu-Zn Massive Sulfide(Urals type) Deposits(Belt IS) (Yenisei Ridge, North-AsianCraton Margin, Russia)This Middle and Late Riphean metallogenic belt is hosted is hosted in the Isakov island arc terrane that contains Middle to Late Riphean rhyolite and basalt. The belt occurs in the northwestern Yenisei Ridge in a synclinorium that extends sublongitudinally along Yenisei River for more than 250 km, and ranges up to 60 km wide. Volcanic and sedimentary rocks consist of basalt porphyry, diabase, andesite, dacite, rhyolite porphyry, and tuff (Kornev and others, 1974). These rocks are metamorphosed to greenschist facies and are intruded by small late Riphean granitoid plutons. The major volcanogenic-sedimentary mn deposit is at Porozhinskoye and the major volcanogenic Cu-Zn massive sulfide deposit is at Khariuzikhinskoye 1. Porozhinskoye 1 Volcanogenic-Sedimentary Mn DepositThis deposit (Golovko, Nasedkina, 1982; Gorshkov, 1994) consists of beds and lenses of rhodochrosite in Vendian chert and carbonate clastic, and pyroclastic rocks with oxidized Mn in various deposits. Host rocks vary from 25 to 85 m thick. Ore horizon contains small beds and lenses of rhodochrosite that locally comprise larger deposits. Twelve deposits, with sizes from hundreds meters to a km long along strike are known. Deposits range from 0.5 to 10 m thick with a average of 2 to 3 m. Rhodochrosite is microcrystalline, is often oolitic, and replaces pyroclastic fragmen. Siderite and dolomite are widespread along with pyrite and apatite. Carbonate ores with 8 to 29% Mn are not ecomically important. Near the surface, primary carbonate ores are oxidized sometimes up to several tens of meters depth. Oxidized ores are: manganite with up to 48% Mn and 7.9% Fe, and pyrolusite and psilomelane with uup to 29% Mn and 28% Fe. Age of oxidized ore formation is Cretaceous and Paleogene. The deposit is large with an average grade of 18.29% Mn. Khariuzikhinskoye 1 Volcanogenic Cu-Zn Massive Sulfide DepositThis deposit (Okhapkin and others, 1976) consists of beds of Zn-Cu sulfides and pyrite that are in late Riphean metamorphosed volcanic and sedimentary rock. Sulfide deposits occur at crest of a brachyanticline and dips 20-50° northwest together with host mafic volcanic rocks and tuff. The deposit is 15 m thick and extends about 60 m along strike. Host mafic lava and tuff are schistose and altered into chlorite-epidote-actinolite rock and pyrite. A gossan occurs at the surface. An association of lenses and layers of oxidized massive sulfide ores and schistose mineralized tuff exists. Primary ore is banded to disseminated, and medium-to fine-grained. Sulfide content ranges up to 80 to 90%. Main ore minerals are pyrite (60-80%), chalcopyrite, pyrrhotite, sphalerite, and bornite. Gangue minerals are quartz, sericite, chlorite, albite, calcite, epidote, biotite, actinolite, barite, and gypsum. The deposit is small with an average grade of 2.86% Cu, 0.38% Zn. Origin and Tectonic Controls for Isakovsk Metallogenic BeltThe volcanogenic Cu-Zn massive sulfide deposit is hosted in metamorphosed rhyolite, andesite, and basalt that are interpreted as forming in an island-arc (Kornev and others, 1974; Kornev, 1985). Mn deposits are hosted in late Riphean and Vendian chert, clastic rock, and carbonates. Metabasalt in an associated ophiolite sequences is MORB or marginal sea type. Rb-Sr age of ophiolite sequence is about 1,260 Ma. Mn deposits are hosted in a late Riphean and Vendian siliceous, carbonate, and clastic sequence. The metallogenic belt is related to an island arc and ophiolite complex that was thrust onto the North Asian Craton Margin in the early Vendian. REFERENCES: Kornev and others, 1974; Kornev, 1985; Golovko and Nasedkina, 1982; Cykin and Kostenko, 1984; Gorshkov, 1994. |