Scheme of mineral facies of metamorphic rocks and its application to the Fennoscandian shield with representative sites of orogenic gold mineralization

Abstract

Our recent studies of metamorphism within the Fennoscandian (or Baltic) Shield area with representative sites of orogenic gold mineralization based on the scheme of mineral facies of metamorphic rocks introduced earlier inspired thorough revision of that scheme. The proposed scheme retains the commonly adopted nomenclature (prehnite-pumpellyite, greenschist, amphibolite, granulite, blueschist and eclogite facies) and is based on thermodynamic calculations and published empirical and experimental data on mineral equilibria in metapelitic and metamafic rocks.We present two simplified maps of Archean and Proterozoic metamorphism, that offer good examples of the application of this improved scheme of metamorphic facies. The maps specify the prevailing metamorphic conditions and their relevant tectonic settings. Gold mineralization of economic interest is spatially associated with low-temperature lowpressure metamorphic terrains metamorphosed at the greenschist to low amphibolite facies of the andalusite-sillimanite facial series.

Keywords

• метаморфическая фация
• метаморфизм
• минеральная ре- акция
• минеральный парагенезис
• р-т условия
• т/р градиент
• орогенное золото
• сдвиговая зона
• аккреционный ороген