By Sergey M. Rodionov1, Alexander A. Obolenskiy2
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Djotsk Metallogenic Belt ofWeathering Crust Mn Deposits(Belt DJ) (Russia, Eastern Siberia)This Late Cretaceous to Paleogene metallogenic belt is hosted in weathered sedimentary rock in the Kizir-Kazir island arc terrane (too small to show at 10 M scale). The metallogenic belt occurs in the East Sayan region and contains several Mn deposits. The major and typical deposit is at Seibinskoye. Seibinskoye 1 Mn DepositThis deposit (Cykin, 1972, 1981, 1988; Matrosov, Shaposhnikov, 1988) consists of Mn oxides in weathering crust that developed on Neoproterozoic siliceous and argillacoues shale. The deposit consists of loose and dense pyrolusite, psilomelane, and limonite. The deposit sharply pinches out at depth. The deposit contains layers of loose oxide Mn minerals that range up to 15 m thick. The layers occur in weathered siliceous and carbonaceous shale along a contact with carbonate strata. The deposit contains about 16 bodies with surface dimensions of 100 by 20 m and 10-12 m thick. The bodies contain about 25% Mn, 9% Fe, 0,4% P, and 37% SiO2. The deposit is medium size with reserves of 110,000 tonnes of ore grading 25% Mn. Origin and Tectonic Controls for Djotsk Metallogenic BeltThe belt is interpreted as forming from weathering crusts developed on Neoproterozoic Mn-bearing rocks. REFERENCES: Cykin, 1967; Matrosov and Shaposhnikov, 1988. Ezop-Yam-Alin Metallogenic Belt ofW-Mo-Be Greisen, Stockwork, andQuartz Vein, Sn-W Greisen, Stockwork,and Quartz Vein, Cassiterite-Sulfide-Silicate Vein and Stockwork, andPorphyry Mo (±W, Sn, Bi) Deposits(Belt EYA) (Russia, Far East)This Late Cretaceous metallogenic belt is related to veins and replacements associated with the Khingan-Okhotsk volcanic-plutonic belt. The deposits occur mainly along the contacts large granite and leucogranite intrusions. K-Ar isotopic ages indicate the Sn deposits and related Sn granite formed between 75 to 100 Ma. The major deposits are at Ippatinskoe, Olgakanskoe, Shirotnoe. Ippatinskoe Sn-W Greisen, Stockwork, and Quartz Vein DepositThis deposit (Ognyanov, 1986) consists of veins and selvages in the northern part of a large granitic body. Sixty-five veins are recognized. The veins range from 2 cm to 2 m wide, extend up to 290 m along strike, and are prospected to a depth of 100 m. The veins occur in a north-south-trending zone that is 3,000 m long and up to 300 m wide. Ore minerals are cassiterite, wolframite, and arsenopyrite, and rare chalcopyrite, pyrite, scheelite, sphalerite, and molybdenite, and very rare bismuthinite and beryl. Gangue minerals are quartz, muscovite, feldspar, fluorite, and rare tourmaline. Deposit contains minor Cu, Ph, Sb, Pb, and Au. Deposit is related to a fine-grained leucogranite with a K-Ar isotopic age of 75 to 90 Ma. The deposit is small with an average grade of 0.31% Sn and 0.19% WO3 in 6 largest veins. Lednikovy-Sarmaka W-Mo-Be Greisen, Stockwork, and Quartz Vein DepositThis deposit (A.I. Bukhanchenko, written commun., 1988) occurs in apical portion of a Late Cretaceous granite pluton and granite-porphyry dikes that intrudes sandstone and siltstone. The deposit consists of a linear stockwork that ranges up to 2 km long and about 300 m wide. The stockwork is composed of quartz and fluorite-topaz-quartz veins and veinlets that vary from 1.0-30.0 cm thick and that occur in an altered zone that contains greisen, chlorite-quartz, and sericite-chlorite-quartz metasomatite. The major minerals are quartz, muscovite, wolframite, arsenopyrite, pyrite, and chalcopyrite. The ore minerals comprise 5 to 40% of veins. The deposit is large with resources of 41,000 tonnes WO3, 28,000 tonnes Cu. Average grade is 0.37% (0.31-0.43%) WO3, and 0.18% (0.14-0.21%) Cu. Origin and Tectonic Controls for Ezop-Yam-Alin Metallogenic BeltThe belt is interpreted as forming during generation of granitoids along along the Khingan transform continental-margin arc consisting of the the Khingan-Okhotsk volcanic-plutonic belt. The arc is tectonically linked to oblique subduction of ancestral Pacific Ocean plate. Fragments of this plate are interpreted as occurring in tectonically interwoven units of the Amur River (AM), Khabarovsk (KB) (younger Early Cretaceous part), and Kiselevka-Manoma accretionary-wedge terranes. This tectonic linkage is based on: (1) occurrence of accretionary-wedge terranes outboard (oceanward) of, and parallel to the various parts of the Khinghan arc; (2) formation of melange structures during the Early and Middle Cretaceous; and (3) where not disrupted by extensive Cretaceous movement along the Central Sihote-Aline strike-slip fault, dipping of melange structures and bounding faults toward and beneath the igneous units of the arc. Formation of the Khingan-Okhotsk magmatic arc is related to subduction that is generally interpreted as ending in the late mid-Cretaceous when oblique subduction changed into sinistral-slip faulting along the outboard margin of the arc. REFERENCES: Natal'in, 1991, 1993; Vrublevsky and others, 1988; Nokleberg and others, 1994, 1998, 2000, 2003; Nechaev and others, 1996; Sengor and Natal'in, 1996. Pilda-Limuri Metallogenic Belt ofSn-W Greisen, Stockwork, andQuartz Vein,W-Mo-Be Greisen, Stockwork,and Quartz Vein, Ag-Sb Vein, PolymetallicPb-Zn ± Cu (±Ag, Au) Vein and Stockwork,and Granitoid-Related Au Vein Deposits(Belt PLL) (Russia, Far East)This Late Cretaceous metallogenic belt is related to veins, replacements, and granitoids related to the Evur zone of the Khingan-Okhotsk volcanic-plutonic belt. The belt occurs at the junction area of the Amgun, Zhuravlevsk-Amur, and Samarka terranes. Several small deposits of different types occur in the belt. The belt contains small deposits at Agnie-Afanasievskoye, Dyapp, and Uchaminskoye. Agnie-Afanasievskoye Granitoid-Related Au Vein MineThis mine (Moiseenko and Eyrish, 1996) occurs in a vein system that ranges up 0.5 km wide and up to 1.0 km long. System occurs in a anticline formed in Early Cretaceous sandstone and siltstone. Several diorite dikes occur along joints that cross host rock bedding. Veins range from 200-700 m long and 5-10 cm wide, strike northeast, and dip moderately. The veins contain mainly quartz, carbonate, feldspar, chlorite, and sericite with up to 1% ore minerals. The ore minerals are pyrite, arsenopyrite, antimonite, chalcopyrite, sphalerite, chalcocite, and gold, and rare cassiterite, wolframite, sheelite, and molybdenite. Pyrite is dominant and forms disseminations and thin veinlets in quartz. The amount of arsenopyrite is less than pyrite and occurs in high-grade zones. Gold grains range from 1-6 mm, and occur in bunches, thin veinlets, and rare octahedron crystals in fractured quartz. Gold fineness is 790. Host rocks are altered near the quartz veins and contain up to 2-4 g/t Au. The deposit is small with production of 12 tonnes Au. Average grade is about 25 g/t Au with a maximum grade 1-2 kg/t Au. Mined from 1936 up to 1962. Dyappe Ag-Sb Vein DepositThis deposit (Moiseenko and Eirish, 1996) consists of low sulfide quartz veins and lesser vein breccia with pyrite, arsenopyrite, antimonite, magnetite, and gold. Pyrite contains from 40-50 g/t up to 1.5 kg/t Au . Ore gold is fine-grained from 0.01-0.1 mm up to 1.2 mm. Au fineness is 600-650. Ore contains Te up to 50 g/t, but Te mineralogy not investigated. Several veins, dipping at 65° to 85° to SE, are prospected. Veins and breccia range from a 4 to 45 cm thick and from 30 to 800 m long. Deposit occurs in the exo-and endocontact zone of diorite stock that intrudes Late Cretaceous black shale. The deposit is small. Primary ore grades up to 5-6 g/t Au, oxidation zone grades up to 200-300 g/t Au. The deposit was mined from 1935 to1938 for Au, and from 1941 to 1942 for Sb. Uchaminskoye Polymetallic Pb-Zn ± Cu (±Ag, Au)Vein and Stockwork DepositThis deposit (V. Kochubey, written commun., 1955; Moiseenko and Eirish, 1996) occurs in folded Early Cretaceous sandstone and siltstone that is intruded by a Late Cretaceous granite porphyry stock and lamprophyre dikes. The deposit occurs in a linear zone of fractured sedimentary rock that is about 1.5 km wide and 0.8 to 30.0 m thick. The zone contains several quartz-sulfide veins that range from 1.5 to 3.0 m thick and linear stockworks. Veins and veinlets consist of fine-grained quartz and sulfides including pyrite, pyrrhotite, and arsenopyrite. The deposit is small with an average grade of 7.0-12.2 g/t Au, 30-70 g/t Ag, 0.5-1.0% Pb, 0.03-0.5% Sn. Origin and Tectonic Controls for Pilda-Limuri Metallogenic BeltThe belt is interpreted as forming during generation of granitoids along along the Khingan transform continental-margin arc consisting of the the Khingan-Okhotsk volcanic-plutonic belt that is related to oblique subduction of ancestral Pacific Ocean plate. REFERENCES: Moiseenko and Eirish, 1996. |