Paleoproterozoic Mafic Dikes in the Junction Zone between the Fenno-Karelian Craton and the Svecofennian Orogen of the Fennoscandinan Shield (Composition, Age, Origin)

Gabbro-dolerite dikes were studied in the junction zone between two structures of different ages of the Fennoscandian shield: the Archean Fenno-Karelian craton and the Raakhe–Ladoga zone. Their composition was analyzed and U-Pb baddeleyite and zircon age was determined for the first time for the Rus...

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Bibliographic Details
Published in:Geochemistry international 2022-11, Vol.60 (11), p.1037-1067
Main Authors: Myskova, T. A., Belyatsky, B. V., Sereda, E. E., Lvov, P. A., Rodionov, N. V., Antonov, A. V., Berezhnaya, N. G., Galankina, O. L.
Format: Article
Language:English
Subjects:
Anomalies
Chronology
Composition
Cratons
Earth and Environmental Science
Earth Sciences
Embankments
Gabbro
Geochemistry
Geochronometry
Isotopes
Niobium
Orogeny
Radiometric dating
Rifting
Rock intrusions
Rocks
Sills
Tectonics
Zircon
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Summary:Gabbro-dolerite dikes were studied in the junction zone between two structures of different ages of the Fennoscandian shield: the Archean Fenno-Karelian craton and the Raakhe–Ladoga zone. Their composition was analyzed and U-Pb baddeleyite and zircon age was determined for the first time for the Russian territory. The Paleoproterozoic age has been established both for the gabbroic rocks of the Fenno-Karelian craton (previously considered Archean) and for the gabbro-dolerites of the Raakhe–Ladoga zone. The dike swarms within the Fenno-Karelian craton were formed in two stages: within 2091 ± 9–2086 ± 6 Ma near the Raakhe–Ladoga zone and in the central part of the studied area and within 1938 ± 6–1933 ± 26 Ma in the northern part. Sills of the Raakhe–Ladoga zone (2081 ± 7 Ma) were formed simultaneously with the earlier dikes of the Fenno-Karelian Craton (2091 ± 9–2086 ± 6 Ma). Primary magmas were derived from different sources. Most of the bodies of the Fenno-Karelian craton have high (La/Lu) N , negative niobium anomalies, predominantly negative εNd values, which suggests a contribution of a metasomatized lithospheric mantle. Some dikes of the Raakhe–Ladoga zone have the same source, but most rocks were obtained by mixing of depleted mantle and more primitive mantle source. The studied gabbrodolerite dikes were likely formed in a rifting tectonic setting.
ISSN:0016-7029
1556-1968
DOI:10.1134/S0016702922110088