The crustal architecture of the Fennoscandian Shield is defined by the cyclic break up and assembly of the Archaean and Paleoproterozoic supercontinents. These global processes resulted in repeated development of geodynamic settings favorable for formation of orogenic gold deposits.
The Archaean Karelian craton (3.5-2.5 Ga) was assembled by the Loppian orogeny (2.8-2.6 Ga). The N-S trending narrow greenstone belts correspond to the suture zones and these belts defines the Ilomantsi, Kuhmo and Oijärvi orogenic gold provinces. Repeated rifting between 2.44-2.05 Ga in the northern part of the Karelian craton led to formation of basins with intracractonic and continental margin sedimentation, multiple emplacement of layered intrusions and mafic dikes, as well as komatiitic and mafic-felsic volcanism. These basins were folded, thrusted and metamorphosed during the accretion of Kola, Karelia and Norrbotten cratons (1.92-1.91 Ga). The Kittilä, Kuusamo-Kuolajärvi and Peräpohja orogenic gold provices are hosted by these basins.
The Svecofennian domain was amalgamated by diachronous accretion (from 1.92-1.91 to 1.89-1.86 Ga) of juvenile arcs (>2.02 Ga to 1.93 Ga), and several micro-continents with ca. 2.1-2.0 Ga age of their basements during the Svecofennian orogeny. Accretion of the Svecofennian domain and the Karelian craton commenced at c. 1.92-1.91 Ga. The final collision between the accreted Fennoscandia (Paleoproterozoic+Archean domains) and Sarmatia (approaching from South) and Amazonia (approaching from West) took place between 1.83-1.79 Ga. The accreted juvenile arcs within the Svecofennian domains host numerous orogenic gold provinces in southern Finland; the Laivakangas and Pirkkala provinces are the most important among them.
Most of the Archean and Paleoproterozoic orogenic gold provinces contains gold-only type of mineralization. However, orogenic gold deposits with atypical metal associations, containing significant concentrations of Cu, Ni, Co, U, Mo and REE, are rather common in the provinces hosted by the folded and thrusted Paleoproterozoic rift-related basins in northern Finland.
The majority of orogenic gold deposits in Finland are hosted by greenschist to middle amphibolite facies metamorphic rocks and very few deposits occur in higher metamorphic grade areas only.
List and major characteristics of Au-only orogenic gold deposits in Finland. (Excel file)
List and major characteristics of orogenic gold deposits with atypical metal associations in Finland. (Excel file)
(Last update: 20.05.2020)
