Age and Sources of Low-Sulfide Gold–Quartz Mineralization of the Karalon Ore Field, North Transbaikalia, Russia: Results of Isotopic–Geochemical (Rb–Sr and Pb–Pb) Studies

The paper presents the results of study of Rb–Sr isotopic system of ore-hosting granitoids, metasomatites after granites, and hydrothermalites of the Upper Karalon gold deposit, as well as the Pb–Pb isotopic system of galena of low-sulfide gold–quartz mineralization of the Karalon gold field. Three groups of ore objects with various Pb isotopic composition of galena are distinguished. Different contribution of mantle and ancient crustal sources is identified for each group. The Pb isotopic composition of galena of the Upper Karalon deposit indicates its genetic link with ore-hosting granites, the age of which (∼600 Ma) could be close to the age of the earliest stage of formation of gold–quartz mineralization. The ancient crustal source is common for the leading gold deposits of North Transbaikalia and exhibits the continental crust parameters of the Siberian Craton at the period of 500–600 Ma. It is established that the Rb–Sr system of the studied rocks and minerals of the Upper Karalon deposit was reconstructed and the Pb isotopes of galena of the Vodorazdel’naya ore zone of the Karalon ore field were redistributed at the boundary of 290–250 Ma. The isotopic data show that the processes of the formation of gold mineralization in geological evolution of the Upper Karalon deposit and Karalon ore field were characterized by long multistage character and accompanied by the regeneration of primary ore concentrations.