Rifting in the Paleoproterozoic Onega Basin: Geochemistry of Volcano–Sedimentary Rocks of the Zaonega Formation

The study of the volcano–sedimentary sequence in the lower part of the Zaonega formation in the Paleoproterozoic Onega structure (Karelian craton, Fennoscandian Shield) has shown that tuffaceous and high-silica rocks predominate in its composition. High-silica rocks (SiO 2 up to 94 wt %) are deplete...

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Published in:Doklady earth sciences 2024-04, Vol.515 (2), p.734-742
Main Authors: Samsonov, A. V., Stepanova, A. V., Guschina, M. Yu, Silaeva, O. M., Erofeeva, K. G., Ustinova, V. V., Maksimov, O. A., Zhdanova, L. R.
Format: Article
Language:English
Subjects:
Basalt
Composition
Cratons
Dikes
Earth and Environmental Science
Earth Sciences
Embankments
Geochemistry
Lithosphere
Phanerozoic
Rifting
Sedimentary rocks
Sediments
Silica
Silicon dioxide
Stratigraphy
Trace elements
Volcanic activity
Volcanic rocks
Volcanoes
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Summary:The study of the volcano–sedimentary sequence in the lower part of the Zaonega formation in the Paleoproterozoic Onega structure (Karelian craton, Fennoscandian Shield) has shown that tuffaceous and high-silica rocks predominate in its composition. High-silica rocks (SiO 2 up to 94 wt %) are depleted in all elements and probably represent chemogenic siliceous silts. Tuffaceous rocks vary broadly in composition and were formed during mixing of tuffogenous basalt material and high-silica chemogenic sediments. In terms of levels of contents and the distribution character of trace elements, tuffogenous rocks are close to N-MORB volcanic rocks. This rock association is typical of the early stages of continental rifting in the Phanerozoic and may indicate the formation of volcano–sedimentary complexes of the Zaonega formation in the environment of continental rifting. The tuffaceous rocks in the lower part of the Zaonega formation are geochemically identical to dolerite dikes and MORB-type volcanic rocks 2.10–2.14 Ga in age. Their formation was probably related to this episode of large-scale extension and thinning of the continental lithosphere of the Karelian craton in the Middle Paleoproterozoic. In this case, the age limit of the Zaonega and underlying Tulomozero formations should be somewhat older than the 2.06–2.10 Ga interval accepted in the modern regional stratigraphic schemes of the Paleoproterozoic Fennoscandian shield.
ISSN:1028-334X
1531-8354
DOI:10.1134/S1028334X23603784