The Ilee Fluorite–Phenakite Ore Occurrence, East Sayan: Contribution of Rift Devonian Magmatism to the Formation of the East Sayan Rare Metal Metallogenic Zone.

One of the richest rare metal provinces in Russia occurs within the Altai–Sayan fold area, which spans the territory of the East Tuva Upland and East Sayan. The deposits of rare metals, elements, and earths formed within the province have different ages and originated in different geotectonic settings and metallogenic epochs. They are related to the intrusion of alkaline rocks, which are abundant along the fault system between the Caledonides of the Altai–Sayan fold area and the Precambrian Tuva–Mongolian Superterrane. The area of their occurrence is also recognized as the East Sayan rare metal metallogenic zone (ESMZ), which originated as a result of the mantle plume impact on the SW frame of the Siberian Platform. These geochemical and geochronological studies were conducted at the Ilee fluorite–phenakite occurrence that formed as a result of the intrusion of granitoids of the Ognit Complex into limestones of the Mongosha Formation, which became a geochemical barrier for a F- and Be-rich magmatic fluid. According to Rb‒Sr and Ar‒Ar geochronological studies, the age of subalkali granite and felsic volcanic rocks of the Ilee Sequence is the Middle Devonian (~390 Ma), which is consistent with the age estimations for rocks of the Ognit Complex. Thus, the coeval age of magmatism and ore formation at the Ilee ore occurrence indicates the contribution of Devonian magmatism to the formation of rare metal mineralization of the ESMZ. [ABSTRACT FROM AUTHOR]