By Sergey M. Rodionov1, Alexander A. Obolenskiy2
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Chelasin Metallogenic Belt ofSn-B (Fe) Skarn (ludwigite),Granitoid-Related Au Vein,Cu (±Fe, Au, Ag, Mo) Skarn,Porphyry Cu-Mo (±Au, Ag). AndPorphyry Cu (±Au) Deposits(Belt CHL) (Russia, Far East)This Late Cretaceous to Paleocene metallogenic belt is related to replacements and granitoids that are part of the Okhotsk-Chukotka volcanic-plutonic belt that intrudes and overlies North Asian Craton and Uda volcanic-plutonic belt. The belt contains several types of granitoid-related deposits. The main deposit is at Chelasin. Chelasin Porphyry Cu (±Au) DepositThe deposit (S.M. Rodionov, A.A. Cherepanov, and E.V. Kurbatov, written commun., 1994) consists of 42 stockwork zones and some quartz-sulfide veins. The zones occur in a single tract that extends about 2.5 km. One zone was dissected by three trenches and varies from 10 to 28 m thick and extends more than 700 m according to geophysical data. The zone splits into several branches at the flanks. The host rocks consist of dacite and andesite flows and numerous dikes of rhyolite, andesite, diorite porphyry, and granodiorite that display silica and propylitic alteration. A K-Ar isotopic age for the altered rock is 64 to 67 Ma years. The deposit is unexplored. Average grades are 1.0-9.4% Cu, up to 10.0 g/t Au, up to 1,119.0 g/t Ag, up to 3.0% Pb, up to 3.0% Zn. Origin and Tectonic Controls for Chalasin Metallogenic BeltThe belt is interpreted as forming during generation of granitoids along an active continental margin arc consisting of the Albian to Late Cretaceous Okhotsk-Chukotka volcanic-plutonic belt. REFERENCES: S.M. Rodionov, this study. Preddzhugdzhursky Metallogenic Belt ofPorphyry Cu-Mo (±Au, Ag),Porphyry Cu (±Au), andAu-Ag Epithermal VeinGranitoid-related Au Vein, andCu (±Fe, Au, Ag, Mo) Skarn Deposits(Belt PRD) (Russia, Far East)This Late Cretaceous to Paleocene metallogenic belt is related to granitoids in the Preddzhugdzhur volcanic zone of the Okhotsk-Chukotka volcanic-plutonic belt that intrudes and overlies the Batomga composite terrane of the East Aldan superterrane, the Dzugdzur anorthosite belt, and the Ulkan plutonic belt. Numerous deposit types occur in the belt and almost all of them are poorly studied. The best studied deposit is at Avlayakan. Avlayakan Au-Ag Epithermal Vein DepositThis deposit (Moiseenko and Eirish, 1996) occurs along the southern flank of Dzhugdzhur district and is hosted in Late Cretaceous dacite, rhyolite, and andesite that overlie Precambrian gabbro and anorthosite. The deposit consists of quartz and quartz-carbonate veins that occur in several sublongitudinal zones. Two zones are well explored. The Central zone varies from 5 up to 40 m thick, is about 3 km long, and consists of quartz and quartz-carbonate veins and veinlets with disseminated gold. Hosted volcanic rocks are altered up to chlorite, sericite, hydromica, and quartz propilite. The average gold content for two intersections is 34.5 and 72.5 g/t Au. The Northeastern zone occurs 450 m north of the Central zone, ranges from 50 to 120 m thick, is 3 km long, and consists of numerous branching quartz veins and breccias with minor sulfides. The average grade is about 10.8 g/t Au for one intersection. The average for the whole deposit is 18.2 g/t Au and 38.1 g/t Ag. Au:Ag=1:2-4. The deposit is small. Origin and Tectonic Controls for Preddzhugdzhursky Metallogenic BeltThe belt is interpreted as forming during generation of granitoids along an active continental margin arc consisting of the Albian to Late Cretaceous Okhotsk-Chukotka volcanic-plutonic belt. REFERENCES: Moiseenko and Eirish, 1996. Belininsk Metallogenic Belt ofBauxite (Karst Type), SedimentaryBauxite, Talc (Magnesite)Replacement, and Laterite Ni Deposits(Belt Bel) (Salair Range, Russia,Eastern Siberia)This Late Cretaceous to Paleocene metallogenic belt is related to weathering of sedimentary rocks in the Salair and Telbes-Kitat island-arc terranes, and ultramafic-mafic bodies in the Alambai accretionary wedge terrane. The belt occurs in the Kuznetsk Alatau and Salair Range and contains several districts. Two types of deposits occur in the belt: (1) karst type bauxite deposits of medium size (Barzasskoye deposit); and (2) laterite Ni deposits of medium size (Belininskoye deposit) (Kuznetsov, 1982). Bauxite deposits are composed of slightly replaced and mottled red beds that are the result of aresidual eluvial weathering crusts. The bauxite formed as a deuterogenic laterite derived from argillic karst. The laterite Ni deposits are related to the ancient weathering crusts developed on serpentinized ultramafic rock. Barzasskoye Bauxite (Karst Type) DepositThis deposit (Kuznetsov, 1982) consists of Cretaceous gibbsite bauxite in a contact karst zone developed in Proterozoic marble that is interlayered with amphibolite. Several tens of bauxite layers vary from 50 by 50 to 800 by 1200 m. The layers are separated by bauxite clays and are underlain by variegated kaolinite clay with brown ironstone lenses. Bauxite structures are clayey, earthy, stony, and pisolitic. Bauxite minerals are gibbsite, kaolinite, goethite, and hematite and intermixed chamosite, siderite, magnetite, ilmenite, hydromica, and quartz. Top parts of bauxite layers grade into light kaolinite clays with relics of gibbsite. The deposit is medium-size with an average grade of 41% Al2O3. Belininskoye Lateritic Ni DepositThis deposit (Minaeva and Bykov, 1974; Kuznetsov, 1982) consists of Ni-bearing weathering crust developed on a ultramafic pluton consists of apodunite, apoperidotite serpentinite, and rare serpentinized pyroxenite.Seventeen layers and funnel-shaped shoots occur. The following deposit types occur: ferruginous-magnesian (1.15% Ni and 0.01% Co); magnesian (1.02% Ni and 0.01% Co); ferruginous-flinty (0.7 to 1.1% Ni and 0.08 to 0.09% Co); and aluminiferous (0.5 to 1% Ni and 0.01 to 0.05% Co). The ore minerals are nontronite, nepouite, serpentine, goethite, hydrogoethite, hematite, kaolinite, Mn oxides and hydroxides, ferrihalloysite, palygorskite, quartz, and chalcedony. The deposit is medium size with an average grade of 15% Ni and 0.01 to 0.09% Co. Origin and Tectonic Controls for Belininsk Metallogenic BeltThe deposits in the belt are interpreted as a deuteric laterite derived from argillic karst material. Laterite Ni deposits formed from of weathering crust developed on serpentinized ultramafic rock. The bauxite deposits occur along Early Late Cretaceous, Late Cretaceous, and Paleogene stratigraphic levels. The bauxite deposits are hosted in basins of early to middle Paleozoic carbonate and alumosilicate rock cut by faults. Bauxite occur in the upper part of a clayey complex. Kaolinite, hydromica, and montmorillonite zones underly bauxite horizons. Bauxite consists of kaolinite, goethite, and gibbsite. Laterite Ni deposits occur along over the Martynovo-Shalap ultramafic pluton that occurs along a major fault zone early Paleozoic volcanic and sedimentary rock. The weathering crust occurs in areal, linear, and karst zones and has ranges from 5 to 300 and more m thick (Minaeva and Bykov, 1974). REFERENCES: Minaeva and Bykov, 1974; Kuznetsov, 1982. |