Gold Deposits of the Yenisei Ridge (Russia) and Age of Its Formation

Siberia is one of the largest in Russia in terms of production and reserves of gold. Large gold deposits, including the world-class ones, are localized here among the Precambrian metamorphic rocks. They belong to two different age types. The first vein gold-quartz type includes a number of deposits with average gold reserves (Eldorado, Ayakhta, Vasilevskoye and others), the largest of them is the Sovetskoye deposit. Ores are represented by low-sulfide quartz veins, vein zones and stockworks with pyrite, arsenopyrite and coarse gold. The second Au-As (± Sb) type is represented by voluminous deposits of disseminated ores of pyrite-arsenopyrite composition with a fine-grained gold in black shales. It includes such unique deposits as Olympiada and Blagodatnoye, as well as a number of large and medium-scale deposits such as Veduga, Poputninskoye, Titimukhta, Bogolyubovskoye, Panimbinskoye, and many others. A specific feature of this type deposits is the spatial coincidence of gold and antimony mineralization of different ages. The latter occurs at all deposits of this type and has commercial importance at the Olympiada and Uderey deposits. The most important and yet unsolved genetic problems of these deposits is determination of their age and relation to magmatism. The recent literature data (Sazonov et al, 2007; Vernikovsky et al, 2006, 2008; Nozhkin et al, 2008, 2011; Vrublevsky et al, 2011, etc.) and our results on the dating of rocks and gold mineralization (U-Pb, Ar-Ar and Re-Os methods) provide a new approach in solving these problems. The age of gold-quartz mineralization of the Sovetskoye deposit established by the newly formed sericite from the quartz-sericite-arsenopyrire (gold-arsenopyrite mineral assemblage) veinlet with native gold intersecting the early metamorphic quartz vein is 820.3 ± 8.2 Ma. The younger recovered high-grade coarse gold in pyrite-muscovite veins intersecting altered shales with arsenopyrite also occur at this deposit. The Ar-Ar age of muscovite from these veins is 775.8 ± 8.1 Ma. The similar age of the early quartz-sericite-arsenopyrite veins with native gold was also established at the Veduga gold deposit (805 ± 6.3 Ma). Based on the available published isotopicgeochronological data and the authors' dating (U-Pb, ArAr, and Re-Os methods) of rocks and ore mineral assemblages from the Olimpiada deposit, we propose the following chronology of Neoproterozoic metamorphic, magmatic, and ore-forming processes: 1) granitoids of the Teya complex: 976 ± 4.7 Ma (UPb); 2) granites of the Tyradinsky intrusion with which rare metal Mo-W mineralization is associated: 894.1 ± 4.7 Ma (U-Pb); 3) regional metamorphism and formation of associated pyrite-pyrrhotite mineral association: > 800-775 Ma (Likhanov et al, 2011, 2013); 4) intrusion of granitoids of the Ayakhta complex, contact metamorphism and associated pyrite-pyrrhotite mineralization: 760-750 Ma (Vernikovsky et al 2006, 2008); 5) mineral assemblages of gold mineralization: goldarsenopyrite, gold-polysulfide and berthierite antimonite, the time span of which is in the interval of 750-650 Ma; The time of formation of gold-arsenopyrite mineralization of the main stage (parageneses with acicular and elongated-prismatic arsenopyrite) have been established using Re-Os dating of the acicular arsenopyrite by isochron is 689 ± 28 Ma (Fig. 1) and close age (Ar-Ar) have the newly formed associating muscovite, which is compatible with the age of alkaline mafic rocks of the Borisenko А.S., Sazonov А.М., Nevolko P.A., Naumov Е.А., Tessalina S., Kovalev К.R. and Sukhorukov V.P., 2014. Gold Deposits of the Yenisei Ridge (Russia) and Age of Its Formation. Acta Geologica Sinica (English Edition), 88(supp. 2): 686-687.