Silurian to Carboniferous Re-Os molybdenite ages of the Kalinovskoe, Mikheevskoe and Talitsa Cu-Mo porphyry deposits in the Urals: implications for geodynamic setting

Abstract

The Urals can be regarded as a significant Cu-Mo-porphyry province, hosting over 30 porphyry deposits. Although their geological structure and ore-forming processes have been studied in great detail, uncertainty remains about their age and related geotectonic setting. In this contribution we report for the first time the Re-Os dating of molybdenites from three Cu-Mo porphyry deposits, namely Kalinovskoe, Mikheevskoe and Talitsa. Three molybdenite samples from the Kalinovskoe deposit yield Silurian Re-Os ages ranging from 427.1 Ma to 431.7 Ma (mean 429.8 ± 4.8 Ma; 2σ standard deviation), and a Re–Os isochron age of 430.7 ± 1.3 Ma (MSWD = 0.63), which coincides with previous U-Pb zircon dating of ore-hosting diorites from the same ore field (427 ± 6 Ma). The molybdenite from the Mikheevskoe deposit gives Re-Os ages of 357.8 ± 1.8 Ma and 356.1 ± 1.4 Ma (mean 357.0 ± 2.4 Ma; Carboniferous/Tournaisian), which corresponds to previous U-Pb dating of zircons from the diorite hosting porphyry deposit (356 ± 6 Ma). The molybdenite from Talitsa Mo-porphyry deposit yields the youngest Re-Os ages of 298.3 ± 1.3 and 299.9 ± 2.9 Ma (mean 299.1 ± 2.3 Ma) at Carboniferous-Permian boundary. Thus, the studied Cu and Mo porphyry deposits are not synchronous and belong to distinct tectonic events of the Urals.