A1 Refereed original research article in a scientific journal
Petrology, geochemistry, and geochronology of the leucogranites in southernmost Finland
Authors: Saukko, Anna; Nikkilä, Kaisa; Eklund, Olav; Fröjdö, Sören; Väisänen, Markku
Publisher: The Geological Society of Finland
Publication year: 2024
Journal: Bulletin of the Geological Society of Finland
Journal name in source: Bulletin of the Geological Society of Finland
Volume: 96
Issue: 1-2
First page : 101
Last page: 134
ISSN: 0367-5211
eISSN: 1799-4632
DOI: https://doi.org/10.17741/bgsf/96.2.001
Web address : https://doi.org/10.17741/bgsf/96.2.001
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/484734167
In the southernmost part of the Svecofennian province in Finland, leucogranites and migmatites stemming from both igneous and sedimentary protoliths reflect the complex magmatic history of the Svecofennian orogeny between 1.89 and 1.82 Ga. Although the migmatites and leucogranites in southernmost Finland display similar ages as their counterparts elsewhere in the Southern Finland Subprovince, they differ in field appearance and composition. Field and petrographical observations reveal K-feldspar megacrysts of varying sizes in the migmatized early Svecofennian (c. 1.89–1.87 Ga) supracrustal rocks and granitoids. Whole-rock geochemical analyses likewise display anomalously high K-contents in the early Svecofennian granitoids. Zircon U-Pb dating of migmatites and related leucogranites shows that a late Svecofennian partial melting event occurred at 1.84–1.82 Ga, possibly in several pulses. The morphological features of the migmatites as well as neosome mineralogy indicate a formation mechanism different from the dehydration melting prevalent elsewhere in the Subprovince.
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We are grateful to reviewers Dr. Åke Johansson and Dr. Raimo Lahtinen and editor Dr. Jarmo Kohonen for their help in improving the manuscript. We thank Martin Whitehouse, Kerstin Lindén and Lev Ilyinsky at the NordSIMS facility for the geochronological analysis; NordSIMS was supported by Swedish Research Council infrastructure grant 2014-06375 at the time of these analyses; this is publication # 775). We also thank Tvärminne Zoological Station for granting us access to the study area. We are grateful to Pietari Skyttä for drone images. Grants from Nordenskiöldsamfundet i Finland, Svenska kulturfonden, Victoriastiftelsen, and the Graduate school at Åbo Akademi University made this work possible. Fieldwork was supported by the K. H. Renlund foundation and Forströmsstiftelsen and the SIMS analysis costs were covered by Åbo Akademis Jubileumsfond 1968.
