The Age and Tectonic Position of Epithermal Gold Mineralization of the Omolon Massif (Northeast Asia)

This paper reports on some aspects of the genesis of industrially important Paleozoic epithermal gold deposits of the Omolon Massif. The Ar–Ar dating of the ores showed that the age of these deposits is 20–30 Ma younger than that of the volcanic complexes of the Devonian Kedon Group, with which this mineralization has been traditionally associated. The stage of post-subduction rifting, characterized by the formation of volcano-plutonic associations of shoshonite-latite series, has been identified for the Paleozoic continental marginal magmatism of the Omolon Massif. These ores were formed during this stage; their chronological boundaries are determined as 335–286 Ma. The paragenetic connection with the rifting-related shoshonite-latite series explains the specific features of the Paleozoic epithermal gold mineralization of the Omolon Massif, including the high gold–silver ratio, a low sulfide content of ore, the widespread development of fluorite and tellurides, and low values of the primary Sr isotope ratio (0.703–0.706).