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 Kianta domain (FIRE 1 CMP 0000–3500)

The Kianta domain (CMP 0000–3500) corresponds to the Neoarchean Lentua complex (Hölttä et al., 2012) that is divided into the eastern Kianta (CMP 0000–2000; Vartius and Kuhmo blocks of Kontinen and Paavola, 2006) and western Kianta (2000–3500; Hyrynsalmi block of Kontinen and Paavola, 2006) blocks by the interlying Kuhmo greenstone belt (e.g., Korja et al., 2006; Lehtonen, 2016).

A major west-dipping tectonic boundary between the crustal blocks has been interpreted to lie on the western margin of the Kuhmo greenstone belt (CMP ~2000; Käpyaho et al., 2006 and references therein, Kontinen and Paavola, 2006).

The eastern Kianta block is dominated by the ca. 2.7–2.8 Ga Haasianvaara suite tonalite-trondhjemite-granodiorite (TTG) series tonalites and greenstone belt remnants, whereas the western Kianta block along the FIRE 1 profile comprises a larger proportion of somewhat younger (ca. 2.68 Ga) granite-granodiorite-monzogranite (GGM) series rocks of the Konivaara suite (Käpyaho et al., 2006; Hölttä et al., 2012).

FIRE 1 References

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