FIRE 4B Geographic constraints

The FIRE 4B runs in an east–west/southeast–northwest direction for 62.5 km from the township of Sirkka in the east to the village of Muonio in the west.

FIRE 4B Geological and tectonic division

The upper crust along the FIRE 4B profile has been divided into two parts: Kittilä (1) and Muonio (2) domains.

Geological description of the Kittilä domain (FIRE 4B CMP 0000–1650)

The Kittilä domain (CMP 0000–1650) corresponds to the Paleoproterozoic metasedimentary and -volcanic sequences of the Central Lapland greenstone belt (CLGB), which are at least partly correlated with the rocks of the Peräpohja schist belt (Lehtonen et al., 1998; Lahtinen et al., 2015 and references therein) and share a similar geological history.

The rocks of the ca. 2.0 Ga Kittilä suite (a.k.a. the Kittilä allochton) form a group of dominantly metavolcanic rocks with diverse geochemical signatures that are inferred to originate in a plume environment and, in contrast to the generally extensional tectonic regime, to have been emplaced in a convergent tectonic event on top of the rift-related supracrustal sequences (Lehtonen et al., 1998; Hanski and Huhma, 2005; Patison et al., 2006; Lahtinen et al., 2015).

The eastern part of the FIRE 4B profile crosses the westernmost part of the Kittilä suite metavolcanic rocks that are also intruded by the Ruskisrova intrusive complex (CMP 1000–1300). The easternmost occurences of the Virttiövaara formations mark the beginning of the Pajala shear zone (Lahtinen et al., 2015) and the western edge of the Kittilä domain.

FIRE 4B References

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Daly, S.J., Balagansky, V.V., Timmerman, M.J., and Whitehouse, M.J., 2006. The Lapland-Kola orogeny: Palaeoproterozoic collision and accretion of the northern Fennoscandian lithosphere. Geological Society of London, Memoirs 32, 579–598.

Hanski, E. and Huhma, H., 2005. Central Lapland Greenstone belt. In: Lehtinen, M., Nurmi, P.A. & Rämö, O.T. (eds.) The Precambrian Geology of Finland − Key to the Evolution of the Fennoscandian Shield. Developments in Precambrian Geology 14, Amsterdam: Elsevier, 139–194.

Hölttä, P., Väisänen, M., Väänänen, J., and Manninen, T., 2007. Paleoproterozoic metamorphism and deformation in Central Lapland, Finland. Geological Survey of Finland, Special Paper 44, 7–56.

Hörmann, P.K., Raith, M., Raase, P-. Ackermand, D., and Seifert, F., 1980. The granulite complex of Finnish Lapland: petrology and metamorphie conditions in the Ivalojoki - Inarijärvi area. Bulletin of the Geological Survey of Finland 308, 95 p.

Kärki, A., Laajoki, K., and Luukas, J., 1993. Major Paleoproterozoic shear zones of the central Fennoscandian Shield. Precambrian Research 64, 207–223.

Lahtinen, R., Korja, A., and Nironen, M., 2005. Proterozoic tectonic evolution. In: Lehtinen, M., Nurmi, P., and Rämö O.T., (eds.). Precambrian Geology of Finland – Key to the Evolution of the Fennsocandian Shield. Developments in Precambrian Geology 14, 481–531.

Lahtinen, R., Huhma, H., Lahaye, Y., Jonsson, E., Manninen, T., Lauri, L.S., Bergma, S. , Hellström, F., Niiranen, T., and Nironen, M., 2015. New geochronological and Sm–Nd constraints across the Pajala shearzone of northern Fennoscandia: Reactivation of a Paleoproterozoic suture. Precambrian Research 256, 102–119.

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Patison, N. L., Korja, A., Lahtinen, R., Ojala, V. J., and the FIRE Working Group 2006. FIRE seismic reflection profiles 4, 4A and 4B: Insights into the Crustal Structure of Northern Finland from Ranua to Näätämö. Geological Survey of Finland, Special Paper 43, 161–222.

Sorjonen-Ward, P., 1993. Structural history, alteration and gold mineralization in the Lapland Greenstone Belt, Finland. In: Mid- to lower-crustal metamorphism and fluids conference, Mount Isa, July 26–August 1, 1993, Geological Society of Australia, Abstracts 35, 88–90.

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Väänänen, J. and Lehtonen, M.I. 2001. U-Pb isotopic age determinations from the Kolari-Muonio area, western Finnish Lapland. Geological Survey of Finland, Special Paper 33, 85–93.

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