Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland
We have reappraised the age and composition of the mid-Proterozoic Häme dyke swarm in southern Finland. The dominant trend of the dykes of this swarm is NW to WNW. Petrographic observations and geochemical data indicate uniform, tholeiitic low- Mg parental magmas for all of the dykes. Nevertheless,...
Published in: | Bulletin of the Geological Society of Finland |
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2022
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ftunivhelsihelda:oai:helda.helsinki.fi:10138/344801 2024-09-15T18:05:59+00:00 Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland Luttinen, Arto Lehtonen, Elina Bohm, Katja Lindholm, Tanja Marjukka Söderlund, Ulf Salminen, Johanna Earth Sciences Unit Petrology and Geochemistry Department of Geosciences and Geography Biological stations Helsinki University Library 2022-06-15T06:38:01Z 27 application/pdf http://hdl.handle.net/10138/344801 eng eng Geological Society of Finland 10.17741/bgsf/94.1.004 Luttinen , A , Lehtonen , E , Bohm , K , Lindholm , T M , Söderlund , U & Salminen , J 2022 , ' Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland ' , Bulletin of the Geological Society of Finland , vol. 94 , no. 1 , pp. 75-101 . https://doi.org/10.17741/bgsf/94.1.004 ORCID: /0000-0002-3129-0392/work/114603328 ORCID: /0000-0001-5347-1920/work/114604847 ORCID: /0000-0002-0122-1927/work/114607802 ORCID: /0000-0001-6115-3359/work/114607902 http://hdl.handle.net/10138/344801 48c23889-38c8-447e-93ab-dd23a5ae0b40 85135321309 000891582300004 cc_by info:eu-repo/semantics/openAccess openAccess Geosciences ID-TIMS geochronology rapakivi magmatism mafic dyke mid-Proterozoic Fennoscandia Other natural sciences Physical sciences Ecology evolutionary biology Environmental sciences Article publishedVersion 2022 ftunivhelsihelda 2024-06-25T14:22:46Z We have reappraised the age and composition of the mid-Proterozoic Häme dyke swarm in southern Finland. The dominant trend of the dykes of this swarm is NW to WNW. Petrographic observations and geochemical data indicate uniform, tholeiitic low- Mg parental magmas for all of the dykes. Nevertheless, the variability in incompatible trace element ratios, such as Zr/Y and La/Nb, provides evidence of changing mantle melting conditions and variable crustal contamination. Our ID-TIMS 207Pb/206Pb ages for four low-Zr/Y-type dykes indicate emplacement at 1639 ± 3 Ma, whereas the most reliable previously published ages suggest emplacement of the high-Zr/Y-type dykes at 1642 ± 2 Ma. We propose that the Häme dyke swarm, and possibly also the other mid- Proterozoic mafic dyke swarms in southern Finland, records a progressive decrease in Zr/Y values due to magma generation under developing areas of thinned lithosphere. We consider that the formation of mafic magmas was most probably associated with the upwelling of hot convective mantle in an extensional setting possibly related to the nearby Gothian orogeny. The generation of tholeiitic magmas below continental lithosphere was probably promoted by the elevated mantle temperature underneath the Nuna supercontinent. We speculate that the origin of most of the relatively small mid-Proterozoic mafic dyke swarms, anorthosites, rapakivi granites, and associated rocks found across Nuna was similarly triggered by extensional plate tectonics and the convection of anomalous hot upper mantle below the supercontinent. Peer reviewed Article in Journal/Newspaper Fennoscandia HELDA – University of Helsinki Open Repository Bulletin of the Geological Society of Finland 94 1 75 102 |
institution |
Open Polar |
collection |
HELDA – University of Helsinki Open Repository |
op_collection_id |
ftunivhelsihelda |
language |
English |
topic |
Geosciences ID-TIMS geochronology rapakivi magmatism mafic dyke mid-Proterozoic Fennoscandia Other natural sciences Physical sciences Ecology evolutionary biology Environmental sciences |
spellingShingle |
Geosciences ID-TIMS geochronology rapakivi magmatism mafic dyke mid-Proterozoic Fennoscandia Other natural sciences Physical sciences Ecology evolutionary biology Environmental sciences Luttinen, Arto Lehtonen, Elina Bohm, Katja Lindholm, Tanja Marjukka Söderlund, Ulf Salminen, Johanna Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland |
topic_facet |
Geosciences ID-TIMS geochronology rapakivi magmatism mafic dyke mid-Proterozoic Fennoscandia Other natural sciences Physical sciences Ecology evolutionary biology Environmental sciences |
description |
We have reappraised the age and composition of the mid-Proterozoic Häme dyke swarm in southern Finland. The dominant trend of the dykes of this swarm is NW to WNW. Petrographic observations and geochemical data indicate uniform, tholeiitic low- Mg parental magmas for all of the dykes. Nevertheless, the variability in incompatible trace element ratios, such as Zr/Y and La/Nb, provides evidence of changing mantle melting conditions and variable crustal contamination. Our ID-TIMS 207Pb/206Pb ages for four low-Zr/Y-type dykes indicate emplacement at 1639 ± 3 Ma, whereas the most reliable previously published ages suggest emplacement of the high-Zr/Y-type dykes at 1642 ± 2 Ma. We propose that the Häme dyke swarm, and possibly also the other mid- Proterozoic mafic dyke swarms in southern Finland, records a progressive decrease in Zr/Y values due to magma generation under developing areas of thinned lithosphere. We consider that the formation of mafic magmas was most probably associated with the upwelling of hot convective mantle in an extensional setting possibly related to the nearby Gothian orogeny. The generation of tholeiitic magmas below continental lithosphere was probably promoted by the elevated mantle temperature underneath the Nuna supercontinent. We speculate that the origin of most of the relatively small mid-Proterozoic mafic dyke swarms, anorthosites, rapakivi granites, and associated rocks found across Nuna was similarly triggered by extensional plate tectonics and the convection of anomalous hot upper mantle below the supercontinent. Peer reviewed |
author2 |
Earth Sciences Unit Petrology and Geochemistry Department of Geosciences and Geography Biological stations Helsinki University Library |
format |
Article in Journal/Newspaper |
author |
Luttinen, Arto Lehtonen, Elina Bohm, Katja Lindholm, Tanja Marjukka Söderlund, Ulf Salminen, Johanna |
author_facet |
Luttinen, Arto Lehtonen, Elina Bohm, Katja Lindholm, Tanja Marjukka Söderlund, Ulf Salminen, Johanna |
author_sort |
Luttinen, Arto |
title |
Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland |
title_short |
Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland |
title_full |
Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland |
title_fullStr |
Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland |
title_full_unstemmed |
Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland |
title_sort |
age, geochemistry, and origin of the mid-proterozoic häme mafic dyke swarm, southern finland |
publisher |
Geological Society of Finland |
publishDate |
2022 |
url |
http://hdl.handle.net/10138/344801 |
genre |
Fennoscandia |
genre_facet |
Fennoscandia |
op_relation |
10.17741/bgsf/94.1.004 Luttinen , A , Lehtonen , E , Bohm , K , Lindholm , T M , Söderlund , U & Salminen , J 2022 , ' Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland ' , Bulletin of the Geological Society of Finland , vol. 94 , no. 1 , pp. 75-101 . https://doi.org/10.17741/bgsf/94.1.004 ORCID: /0000-0002-3129-0392/work/114603328 ORCID: /0000-0001-5347-1920/work/114604847 ORCID: /0000-0002-0122-1927/work/114607802 ORCID: /0000-0001-6115-3359/work/114607902 http://hdl.handle.net/10138/344801 48c23889-38c8-447e-93ab-dd23a5ae0b40 85135321309 000891582300004 |
op_rights |
cc_by info:eu-repo/semantics/openAccess openAccess |
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Bulletin of the Geological Society of Finland |
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94 |
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75 |
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