The Archaean nucleus of the Fennoscandian (Baltic) Shield

Abstract

Archaean supracrustal complexes, known in the Fennoscandian (Baltic) Shield, are described and discussed by analysing the time sections 3.1-2.9, 2.9-2.75 and 2.75-2.65 Ga. Data on granitoid complexes, interrelated in time and space, and evidence for Archaean metamorphic events are classified and presented briefly. Fragments of ophiolitic and eclogitic associations have been found in Archaean rocks in the Shield. The first evidence of continental crust in the Shield is from Meso-Archaean time (3.5-3.1 Ga); isolated microcontinents, such as Vodlozero, lisalmi and North Finland, have been identified. New continental crust was mainly generated in the 2.9-2.65 Ga interval. The geodynamic settings in which the continental crust was formed in the Meso-and Neoarchaean included subduction (ensialic and ensimatic), accretion and collisional mechanisms. The continental and oceanic crust were affected by mantle plumes.

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

“…The Salma eclogite association is structurally linked with the Central Belomorian greenstone belt separating the Inari-Kola and Khetolambina tectonic units. It is formed by a mafic-ultramafic ophiolite type sequence dated at 2.88-2.85 Ga [Bibikova et al, 1999;Slabunov et al, 2006]. Mafic magma injections into the crust of the active margin, which led to formation of the Gridino dike swarm, were associated with immersion of a midocean ridge in the subduction zone, starting from ~2.87 Ga. Crustal delamination of the active margin and subsequent involvement of the lower crust in subduction 2.87-2.82 Ga ago, led to high-pressure metamorphism of the Gridino dikes that reached eclogite-facies conditions during the collision event between 2.82 and 2.78 Ga. As a result, the Karelia, Kola, and Khetolambina blocks were consolidated, and the Mesoarchaean Belomorian accretionary-collisional orogen was formed.…”

Geochronology of the Palaeoproterozoic Kautokeino Greenstone Belt, Finnmark, Norway: Tectonic implications in a Fennoscandia context

“…The Fennoscandian Shield hosts a rich geological record of the Archaean to Palaeoproterozoic evolution of the Earth (Daly et al, 2006;Slabunov et al, 2006;Hölttä et al, 2008). In the northeastern part of the shield (Fig.…”

Crustal seismic structure and depth distribution of earthquakes in the Archean Kuusamo region, Fennoscandian Shield

“…The Salla greenstone belt is situated at the SW-dipping Northern-Karelia suture zone (NKS), an Archean boundary separating the Belomorian mobile belt (BMB) from the Karelian craton (Slabunov et al, 2006). The anomaly is well covered from the south, south-east and west by lines 1, 2, 4 and 5, as well as by the two Russian profiles KU and PK (Figs.…”