40Ar/39Ar Age of Gold Ore Metasomatites of the Albyn Deposit, Mongol–Okhotsk Fold Belt

Abstract

The paper reports the results of 40Ar/39Ar geochronological studies of the muscovite–quartz–albite metasomatites of the ore bodies and host rocks of the Albyn deposit located in the Selemdzha–Kerbi structural zone of the eastern part of the Mongol–Okhotsk Fold Belt. To a first approximation, the age of the hydrothermal ore process responsible for the formation of the Albyn deposit can be estimated within an interval of 131–130 Ma. At the same time, we cannot exclude the existence of an earlier stage of this process at ~135 Ma, although this assumption requires further substantiation. A close age estimate (~134–130 Ma) was obtained earlier for the ore metasomatites of the Malomyr deposit located in the same structural zone. There are no data on the magmatic manifestations of close age within the considered region, which makes it impossible to relate the ore mineralization of the Albyn deposit with magmatic processes. At the same time, the age of the thermal event superimposed on the host rocks of the Afanasiev Formation is 131 ± 3 Ma, which likely indicates the regional nature of this event. We suggest that a significant role in the mobilization, redistribution of ore matter, and formation of the Albyn deposit was played by large-scale deformations accompanied by hydrothermal activity.