Oligocene shoshonitic rocks of the Rogozna Mts. (Central Balkan Peninsula): Evidence of petrogenetic links to the formation of Pb–Zn–Ag ore deposits

This study focuses on age and evolution of the Oligocene quartz latite of the Rogozna Mts. (Central Balkan Peninsula), in order to better understand the link between magmatism and formation of Pb–Zn ± Ag mineralization. New 40Ar/39Ar biotite and amphibole plateau ages suggest that the Rogozna Mts. quartz latite originated through a continuous volcanic episode from 27.3 ± 0.1 to 29.5 ± 0.1 Ma which was immediately followed by a hydrothermal phase. The quartz latites are hypocrystalline porphyritic with phenocrysts and microphenocrysts (~ 60 vol.%) of plagioclase (An37–49), biotite Mg# [100 × Mg / (Mg + Fetot)]  850 °C–~720 °C and injection of lamproite-like melts. The injection causes an increase of temperature and a decrease of viscosity of the resulting hybrid magma, facilitating its upwelling and triggering pyroclastic eruptions. The addition of new volatiles by lamproitic melts most probably established the conditions for a hydrothermal phase above the magma chamber that was previously degassed explosively. This implies that magma mixing processes can be of great importance for the formation of Pb–Zn deposits. Similar processes are likely to have occurred in other areas with economically significant Pb–Zn–Ag ± other metal mineralization in the region of the Central Balkan Peninsula (Veliki Majdan, Rudnik, Golija, Kopaonik, Avala, etc.).