Subduction, exhumation, and resubduction in the Scandinavian Caledonides: studying the deep levels of a Himalaya-type orogen
Final Report Abstract
High- and ultrahigh-pressure (HP and UHP) metamorphic rocks from the Seve Nappe Complex and the Tromsø Nappe in the Scandinavian Caledonides were studied using methods of structural geology, metamorphic petrology, and Lu-Hf garnet dating. In the Seve Nappe Complex, UHP metamorphism was not restricted to single localities or rock types but affected entire, large terrains. Similar UHP conditions recorded by rocks of various composition and rheology (garnet peridotite, eclogite, felsic gneiss) show that ultrahigh pressure did not result from amplification of non-lithostatic pressure at moderate depth but indeed reflects subduction of continental crust to mantle depth. Peak-pressure conditions were reached at 460-450 Ma (Jämtland), 488-480 Ma (Norrbotten), and ca. 448 Ma (Tromsø), in all cases preceding the Laurentia-Baltica continent collision which started at 430 Ma. Deep subduction of continental crust occurred during arc-continent or microcontinent- continent collisions associated with the consumption of the Iapetus Ocean, probably on both sides of the ocean (SNC and Tromsø). The different timing of HP/UHP metamorphism in Jämtland and Norrbotten was confirmed by Lu-Hf dating and resulted from an irregularity of the Baltica-Iapetus continental margin, either a promontory or a microcontinent.
Publications
- (2017): Microdiamond on Åreskutan confirms regional UHP metamorphism in the Seve Nappe Complex of the Scandinavian Caledonides. Journal of Metamorphic Geology, 35, 541-564
Klonowska, I., Janák, M., Majka, J, Petrík, I., Froitzheim, N., Gee, D.G., Sasinkova, V.
(See online at https://doi.org/10.1111/jmg.12244) - (2017): Middle Ordovician subduction of continental crust in the Scandinavian Caledonides – an example from Tjeliken, Seve Nappe Complex, Sweden. Contributions to Mineralogy and Petrology, 172,103
Fassmer, K., Klonowska, I., Walczak, K., Andersson, B., Froitzheim, N., Majka, J., Fonseca, R.O.C., Münker, C., Janák, M., Whitehouse, M.
(See online at https://doi.org/10.1007/s00410-017-1420-7) - (2019) : Monazite behaviour during metamorphic evolution of a diamond-bearing gneiss : a case study from the Seve Nappe Complex, Scandinavian Caledonides. Journal of Petrology, 60, 1773-1796
Petrík, I., Janák, M., Klonowska, I., Majka, J., Froitzheim, N., Yoshida, K., Sasinková, V., Konecný, P., Vaculovic, T.
(See online at https://doi.org/10.1093/petrology/egz051) - (2020): Lu-Hf geochronology of ultra-high-pressure eclogites from the Tromso-Nappe, Scandinavian Caledonides: evidence for rapid subduction and exhumation. International Journal of Earth Sciences
Fassmer, K., Martinet, I., Miladinova, I., Sprung, P., Froitzheim, N., Fonseca, R.O.C., Münker, C., Janák, M., Kullerud, K.
(See online at https://doi.org/10.1007/s00531-020-01866-0) - (2021): Diachronous collision in the Seve Nappe Complex : Evidence from Lu-Hf geochronology of eclogites (Norrbotten, North Sweden). Journal of Metamorphic Geology, 39, 819-842
Fassmer, K., Froitzheim, N., Janák, M., Strohmeyer, M., Bukala, M., Lagos, M., Münker, C.
(See online at https://doi.org/10.1111/jmg.12591)
