Timing of Ore Mineralisation in Deposits of the Baikal-Muya Belt and the Barguzin-Vitim Super-Terrain (Transbaikalie)

The study was aimed at dating of Au ores from the Yubileinoe, Irokinda and Uryakh deposits located in the Baikal-Muya fold belt and Pb-Zn ores from the Ozernoe deposit in the Barguzin-Vitim super-terrain (Transbaikalia, Russia). The 40Ar/39Ar ages on pyrite-encapsulated sericite of gold-bearing quartz sampled from veins in the Yubileinoe, Irokinda and Uryakh deposits are 265 ± 33 Ma, 276 ± 13 Ma and 287 ± 7 Ma, respectively. The age of disseminated mineralisation in the Ozernoe deposit is 329 ± 19 Ma. The results of this study and previously published data suggest two stages of ore mineralisation at Transbaikalia: 330–320 Ma for the disseminated mineralisation and 290–270 Ma for the vein mineralisation. Irrespective of the location and the nature of the host rocks, the former and the latter mineralisation are transiently associated with the initial and final stages of the emplacement of the Angara-Vitim granitic batholith. The granitoids provided heat and possibly fluids, while Au, Pb and Zn were sourced from the host rocks. Gold deposits to the north and south of the batholith are generally older and younger, respectively, and were formed by different geological processes.