40Ar/39Ar Geochronology of Alkaline Rocks of the Inagli Massif (Aldan Shield, southern Yakutia)

Abstract

—The Inagli zoned ring massif is located in the Central Aldan ore district. The close localization of ultrabasic and alkaline potassic rocks, magmatism, and mineralization (platinum, gems Cr-diopside, and vermiculite) make this object unique from both geological and economic perspectives. Formation of alkaline rocks in the Inagli massif was related to the Mesozoic tectonomagmatic activation of the Aldan Shield and occurred in several stages. Intrusion of clinopyroxenites took place no later than 145.8 ± 3.2 Ma, whereas most of alkaline rocks of the ring framing formed at 133–128 Ma. The feldspar-Cr-diopside-mica veins in the dunite core are dated at 133.4 ± 1 Ma.