FIRE 1 Geographic constraints

The eastern part of the 500 km long FIRE 1 line runs east to west and transects the Neoarchean Lentua complex (Hölttä et al., 2012) that includes the Eastern and Western Kianta blocks separated by the Kuhmo greenstone belt (Korja et al., 2006).

Towards the west the profile crosses the Paleoproterozoic Kainuu belt and the intertwining slivers of the prominently Archean Kalpio (Kajaani), Manamansalo, and Rautavaara complexes (Hölttä et al., 2012). Further to the southwest, the profile crosses the partly Mesoarchean Iisalmi complex (Hölttä et al., 2012) and the Archean–Proterozoic boundary to the Paleoproterozoic Savo belt.

The profile continues southwestward, towards the center of the Paleoproterozoic Central Finland Granitoid Complex and terminates north of the town of Keuruu in Central Finland.

FIRE 1 Geological and tectonic division

The upper crust along the FIRE 1 profile has been divided into five parts: The Kianta (1), Kainuu (2), Iisalmi (3), Savo (4), and Keitele (5) domains.

Geological description of the Keitele domain (FIRE 1 CMP 11000–20000)

The Keitele domain (CMP 11000–20000) corresponds roughly to the area of the Central Finland granitoid complex (CFGC) that comprises a variety of orogenic, dominantly I-type granitic rocks and minor associated supracrustal rocks with a relatively evolved geochemical character (Nironen, 2005).

Majority of the CFGC consists of 1.89 to 1.87 Ga calc-alkaline granodiorites and granites synkinematic with the major orogenic stage corresponding to the collision of the Southern Finland arc complex (Bergslagen microcontinent and the Häme belt of the southern Svecofennia sub-province; Lahtinen et al., 2016) with the Western Finland arc complex (Keitele and parts of the presumed Bothnian microcontinents or the central Svecofennia sub-province; Lahtinen et al., 2016) at ca. 1.9 Ga.

The 1.88 to 1.86 Ga postkinematic granitic rocks with more alkaline geochemical character (Nironen, 2005) form smaller, often discordant, intrusions with transitional I- to A-type characteristics and can be divided into three geochemical types (types 1, 2, and 3; e.g., Elliott, 2003 and reference therein).

FIRE 1 References

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