University of Oulu

Chopin, F., Korja, A., Nikkilä, K., Hölttä, P., Korja, T., Abdel Zaher, M., et al. ( 2020). The Vaasa migmatitic complex (Svecofennian orogen, Finland): Buildup of a LP‐HT dome during Nuna assembly. Tectonics, 39, e2019TC005583.

The Vaasa migmatitic complex (Svecofennian Orogen, Finland) : buildup of a LP‐HT dome during nuna assembly

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Author: Chopin, Francis1,2,3; Korja, Annakaisa1; Nikkilä, Kaisa1,4;
Organizations: 1Department of Geosciences and Geography, University of Helsinki, Helsinki, Finland
2Université de Strasbourg, CNRS, IPGS UMR 7516, Strasbourg, France
3Center for Lithospheric Research, Czech Geological Survey, Prague, Czech Republic
4Geology and Mineralogy, Åbo Akademi University, Turku, Finland
5Geological Survey of Finland, Espoo, Finland
6Faculty of Technology, Oulu Mining School, Applied Geophysics, University of Oulu, Oulu, Finland
7Now at Exploration Geophysics, Geosciences and Environmental Engineering, Luleå University of Technology, Luleå, Sweden
8Now at Geomagnetic and Geoelectric Department, National Research Institute of Astronomy and Geophysics, Helwan, Egypt
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 9.7 MB)
Persistent link:
Language: English
Published: American Geophysical Union, 2020
Publish Date: 2020-07-24


Tectonic evolution of the Paleoproterozoic Vaasa migmatitic complex (VMC) in the central part of the Svecofennian accretionary orogen is deciphered using aeromagnetic and gravity maps, deep seismic and magnetotelluric profiles, and structural and metamorphic data. The VMC is a semicircular structure with migmatitic rim and granitic core composed of several subdomes. It evolved in three main tectonic events (D1–D3). The D1 event (ca. 1.89–1.88 Ga) corresponds to the stacking of supracrustal rocks and the formation of an inverted metamorphic gradient. Anatexis at LP‐HT metamorphic conditions enabled the material to flow. The D2 event (ca. 1.88–1.87 Ga) corresponds to large‐scale folding of the partially molten crust within an orocline. It is marked by folds with an E‐W vertical axial planar foliation. The late D3 event resulted from mass redistribution owing to mechanical instabilities within the hinge of the orocline. It is marked by vertical shearing (ca. 1.87–1.85 Ga) in the marginal parts of the complex and along the granitoid subdomes. The seismic reflection profile (FIRE 3a) and magnetotelluric profiles (MT‐PE and MT‐B2) image large‐scale D1 stacking structures within an accretionary prism. Near vertical breaks in crustal‐scale reflectivity and conductivity models are interpreted as D3 shear zones. The VMC is an example of early mass and heat transfer within a collage of hot supracrustal rocks in an accretionary belt. Partial melting enhanced the flow of material, the production, and rise of magma as well as exhumation, marked by magmatic domes in the hinge of the orocline.

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Series: Tectonics
ISSN: 0278-7407
ISSN-E: 1944-9194
ISSN-L: 0278-7407
Volume: 39
Issue: 3
Article number: e2019TC005583
DOI: 10.1029/2019TC005583
Type of Publication: A1 Journal article – refereed
Field of Science: 1171 Geosciences
Funding: This work has been supported by the Academy of Finland through the MIDCRUST consortium 139035, 139549, and 139516. We thank the University of Oulu for the researcher exchange grants to M. A. Zaher. We also acknowledge the grants from the K.H. Renlund's Foundation to MIDCUST consortium. We thank the IPGS UMR 7516 for its financial support.
Academy of Finland Grant Number: 139516
Detailed Information: 139516 (Academy of Finland Funding decision)
Dataset Reference: FIRE data are published in OpenFIRE application (, and Broadband magnetotelluric data (MT‐PE and MT‐B2) are available in the EPOS‐ERIC Thematic core service repository (http://ics‐c.epos‐
Copyright information: © 2020. American Geophysical Union. All Rights Reserved.