Evolution of Endogenic Regimes and Stages of Gold Ore Formation in the Kostomuksha Greenstone Belt, Karelia

摘要

The Kostomuksha greenstone belt (KGB) is the major prospective gold ore district in Karelia (figure). New mobilistic ideas concerning the geology and Late Archean geodynamic evolution of this structure have been developed in recent years. They differ from one another in the details, but, in general, they suggest that it was formed in two stages, including a protorifto-genic stage (origin and evolution of an intracontinental or oceanic rift) and an erogenic stage (accretionary collision). In contrast to the previously accepted scheme, the new stratigraphical classification of the accreted Upper Archean (Lopian) Complex based on geo-chronological, stratigraphic, and structural data includes the lower ultramafic-mafic (Niemijarvi and Ruvinvaara formations), middle (Shurlovaara Formation), and upper (Gimoly Group) sequences. Taking this classification and the results of our metallogenic studies into account, one can outline the stages of meta-somatic alteration and gold mineralization and define the factors controlling localization of commercial-grade ores.