The Age of the Kubaka Epithermal Gold-Silver Deposit (Omolon Massif, Northeast Russia): Geological and Isotopic-Geochronological Constrains (U-Pb and Ar-40/Ar-39 Methods)

摘要

New data are obtained on the age of the epithermal gold-silver mineralization of the Kubaka deposit (Omolon Massif, Northeast Russia). Our geological observations in the open-pit mine of the Zokol zone of the deposit allow us to conclude that the mineralization formed between the eruptions of Upper Devonian ore-hosting volcanites of the Kedon series (zircon U-Pb age 370 +/- 2.5 Ma, SHRIMP) and Lower-to-Middle Jurassic trachybasalts and picrobasalts of the Omolon Complex (Ar-40/Ar-39 plateau age of 179 +/- 8 Ma) without the vein penetrating into the Carboniferous Corba Formation. The Ar-40/Ar-39 plateau age for a white adularia from the productive quartz vein yielded 299 +/- 3.5 Ma (MSWD = 0.91, p = 0.43, 66% of Ar-39 released in four steps). Our results contradict a commonly accepted concept of "polychronous" ore formation (during the Carboniferous and Cretaceous) or long-term mineralization at the Kubaka deposit, and likely indicate a high probability of at least an Upper Carboniferous upper age limit of epithermal gold mineralization.