Siliceous-Alkaline Metasomatites in the Precambrian Basement of the Torsko-Apsat Ore Cluster (Transbaikalia): Types, Position, and Role in Ore Genesis

Abstract In the Archean basement of the Torsko-Apsatsky ore unit, in the process of prospecting and appraisal work for gold, a repeated manifestation of metasomatic processes involving potassium, realized in the form of siliceous-alkaline metasomatites, gumbeite, eisites, was established. The petrographic composition of metasomatites and their role in the formation of gold ore mineralization have been studied. An opinion was expressed on the genetic unity of eisites and gumbeites, as well as on the origin of gold-bearing gumbeites as products of the genetically independent and geochemically specialized alkaline potassium system of the sublithospheric level regionally manifested in the Mesozoic Aldan-Stanovoy geoblock.