Lapland Granulite Belt–Neoarchean subduction zone in the North-Eastern Baltic shield

Abstract

ABSTRACT This paper represents a geological review of the Lapland Granulite Belt (LGB). Description of the general geological framework of the LGB complex is coupled with reviews of the geochronological data, metamorphism, mineral endowment and concludes with a discussion of the geotectonic models. It is shown that the belt was formed in the Neoarchean (2703 ± 9 Ma using the U-Pb method) and consists of two compositionally different units. The lower member with dominating amphibolites is interpreted as metamorphosed volcanics, while the upper member is mainly composed of metamorphosed sandstones. It is noted that the composition and structure of the LGB complex are broadly consistent with typical Phanerozoic island-arc complexes. An interpretation of the LGB complex as a Neoarchean island-arc system is proposed. It is consistent with existing geodynamic interpretations of the adjacent terrains and, in general, fits the global geodynamic model of the supracrustal Archean complexes in the Baltic Shield.