Composition and Age of Atypical Zircon–Titanomagnetite Ores of the Tret’yakovskoe Gold–Fluorite Deposit, West Transbaikalia

Atypical zircon–titanomagnetite ores were found within the ore field of the Tret’yakovskoe gold–fluorite deposit, which is part of the Gilberi gold–silver–fluorite–rare metal ore cluster. The veined quartz–fluorite bodies (vein zones) that form the deposit are areas of massive metasomatic argillization, fluoritization, and silicification 0.3–1.0 m thick (rarely, up to 2.3 m). A higher Au content is a peculiarity of quartz–fluorite ores of this deposit. According to exploration data, the Au and Ag contents of ores are 0.3–19.5 g/t (3 g/t, on average) and 1.9–18.6 g/t (7 g/t, on average), respectively. The zircon–titanomagnetute ores are composed of an aggregate of Fe–Ti minerals with rare fine quartz–chlorite veinlets and numerous euhedral zircon crystals and rare dissemination of apatite, quartz, and monazite. The U–Pb LA-ICP-MS isotopic age of zircon of 277 ± 1.5 Ma corresponds to the age of the West Transbaikalia rifting magmatism. The finding of zircon–titanomagnetite ores associated with gold–fluorite mineralization indicates the possibility of finding a new type of complex ores on the territory of Transbaikalia similar to South Australian noble metal ores.