@article{15af63e7ab2e4a04a485a48c887e7290,
title = "Large-scale, flat-lying mafic intrusions in the Baltican crust and their influence on basement deformation during the Caledonian orogeny",
abstract = "The Fennoscandian Shield in central Sweden displays a complex structural and compositional architecture that is mainly related to the Proterozoic history of the Baltica paleocontinent. In its western parts, the Precambrian basement is covered by the allochthonous rocks of the Caledonide orogen, and direct information about the underlying crust is restricted to a few unevenly distributed basement windows in western Sweden and Norway. In this study, we use preliminary results from the second borehole of the Collisional Orogeny in the Scandinavian Caledonides project (COSC-2), new gravity data, forward gravity, and magnetic modeling and interpretation of seismic reflection profiles to assess the 3-D architecture of the basement. Our results reveal a wide (∼100 km) and dense network of mainly flatlying and saucer-shaped dolerites intruding the volcanic and granitic upper crustal rocks of the Transscandinavian Igneous Belt. Similar intrusion geometries related to 1.2 Ga dolerites can be recognized in the Fennoscandian Shield. We discuss that the formation of these sill complexes occurred in a lithologically and structurally heterogeneous crust during transtension, which is in disagreement with the current understanding of sill emplacement that involves crustal shortening, layering, or anisotropy of the host rock. Our seismic interpretation and the structural observations from the COSC-2 drilling show that part of the Caledonian-related basement deformation was localized along the margins of the dolerite sheets. We propose that the dolerite intrusion geometry, akin to a flat-ramp geometry, guided the basement deformation during the Caledonian orogeny.",
author = "Rodolphe Lescoutre and Bjarne Almqvist and Hemin Koyi and Th{\'e}o Berthet and Peter Hedin and Olivier Galland and Sonia Brahimi and Henning Lorenz and Christopher Juhlin",
note = "Funding Information: This study benefited from the support of the Swedish Research Council (VR project 2018-03414) and the International Continental Scientific Drilling Program (ICDP). COSC-2 used the Riksriggen national research infrastructure for scientific drilling (Sweden) and was supported by the ICDP, the Swedish Research Council, the German Science Foundation, and the National Science Centre Poland. The authors thank Petroleum Experts Limited for providing us with the Move software academic license. We thank all who participated in the COSC-2 drilling project. R. Lescoutre thanks David Gee for the interesting discussions about the geology of the J{\"a}mtland region, as well as Mohsen Bazargan and George Westmeijer for their company at the drill site. We thank Craig Magee and an anonymous reviewer for thoughtful comments that helped to improve the clarity of the manuscript Funding Information: This study benefited from the support of the Swedish Research Council (VR project 2018-03414) and the International Continental Scientific Drilling Program (ICDP). COSC-2 used the Riksriggen national research infrastructure for scientific drilling (Sweden) and was supported by the ICDP, the Swedish Research Council, the German Science Foundation, and the National Science Centre Poland. The authors thank Petroleum Experts Limited for providing us with the Move software academic license. We thank all who participated in the COSC-2 drilling project. R. Lescoutre thanks David Gee for the interesting discussions about the geology of the J{\"a}mtland region, as well as Mohsen Bazargan and George Westmeijer for their company at the drill site. We thank Craig Magee and an anonymous reviewer for thoughtful comments that helped to improve the clarity of the manuscript. Publisher Copyright: {\textcopyright} 2022 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license",
year = "2022",
month = nov,
doi = "10.1130/B36202.1",
language = "British English",
volume = "134",
pages = "3022--3048",
journal = "Bulletin of the Geological Society of America",
issn = "0016-7606",
publisher = "Geological Society of America",
number = "11-12",
}