MESOARCHEAN TO PALEOPROTEROZOIC CRUSTAL EVOLUTION OF THE BELOMORIAN PROVINCE, FENNOSCANDIAN SHIELD, AND THE TECTONIC SETTING OF ECLOGITES
A.I. Slabunov1, V.V. Balagansky2, A.A. Shchipansky3
1Institute of Geology, Karelian Research Center of the Russian Academy of Sciences, ul. Pushkinskaya 11, Petrozavodsk, 185910, Russia
2Geological Institute, Kola Science Center of the Russian Academy of Sciences, ul. Fersmana 14, Apatity, 184209, Russia
3Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia
Keywords: Eclogite, Archean, Paleoproterozoic, subduction, collision, tectonic collage, orogeny, diamond, Belomorian Province, Lapland-Kola orogen, Fennoscandian Shield
Abstract
The Belomorian Province (BP) of the Fennoscandian Shield is a high-grade metamorphic belt composed of Meso- to Neoarchean tonalite-trondhjemite-granodiorite (TTG) gneisses with subordinate supracrustal complexes. The Belomorian crust is underlined by a thick mantle keel, a structural element typical of Archean cratons. Belomorian rocks were metamorphosed under conditions of mainly high-pressure amphibolite to granulite facies in the both Archean and Paleoproterozoic times. The TTG gneisses contain numerous blocks of almost completely retrogressed eclogite (eclogite-1). This paragenetic association of eclogite-1 and gneisses can be classified as an Archean eclogite-TTG gneiss mélange, a component of the Belomorian continental crust produced by subductional, accretionary, and collisional processes of the Belomorian collisional orogeny 2.9-2.66 Ga ago. The Paleoproterozoic history of the BP comprises two prominent tectonic periods: (i) early Paleoproterozoic (~2.5-2.4 Ga), related to a superplume, and (ii) late Paleoproterozoic (2.0-1.85 Ga), resulted from crustal reworking during the Lapland-Kola collisional orogeny that produced strong penetrative metamorphic and local deformational overprint. The Paleoproterozoic highest-grade metamorphic overprint is represented by patches of eclogites (eclogite-2) in Paleoproterozoic mafic dikes and eclogite-1. Field relations between eclogite-1 and eclogite-2 are described in the Gridino area of the western coast of the White Sea. So, the BP is a high-grade polymetamorphic belt formed by a superposition of the Neoarchean Belomorian and Paleoproterozoic Lapland-Kola orogenies, whose characteristic features are eclogites produced by subduction and collision.
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