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dc.date.accessioned2019-09-11T12:12:25Z
dc.date.available2019-09-11T12:12:25Z
dc.date.issued2019
dc.identifier.urihttp://hdl.handle.net/10852/70340
dc.description.abstractIn the Late Neoproterozoic the supercontinent Rodinia started to disintegrate, and the continents Baltica and Laurentia began to rift apart to form the Iapetus Ocean. Early stages of subsidence caused by ductile stretching of the middle crust led to deposition of a clastic sedimentary succession, which transitioned into shallow marine carbonates. Locally evaporite deposits and stromatolites are present and indicate deposition in an arid environment at low latitudes. This unit was directly overlain by a glaciogenic diamictite, correlated with the 635 Ma Marinoan glaciation, showing the turbulent climatic situation in the Neoproterozoic. Onset of rifting is presumably marked by a sudden change in sedimentary detritus and the deposition of a > 2 km thick formation of shallow marine sandstone. This entire sedimentary succession is cut by mafic dykes that were emplaced around 606 Ma. The sedimentary succession had then been buried to c. 8-14 kilometers depth, as constrained by geothermobarometry. The geochemical signature of the dyke swarm suggests that the magma formed above a zoned mantle with temperatures at the Lithosphere-Asthenosphere Boundary (LAB) c. 75 to 250°C higher than normal. During the dyke emplacement event the thermal structure of the crust changed dramatically because of the heat brought by the mafic magma. The ambient temperatures in the host rock reached 650-700°C, enough to cause partial, contact metamorphic melting of the host rock. Field observations indicate that whereas some early dykes show brittle features, the emplacement of others was accommodated by significant ductile mechanisms as well. Crustal anatexis of some areas, however, occurred already 5 million years prior to dyke emplacement and lasted until the dykes were emplaced. This suggests that a high geothermal gradient was established before the dyke swarm intruded, possibly because of a blanketing effect caused by the platform sedimentary succession and/or incipient lower crustal magma underplating. During the dyking event the magma influx rate was larger than the tectonic stretching rate, which caused the influx of magma to inflate the crust and locally led to a 27% vertical thickening as well as 94% horizontal extension. This shows that the magma was not passively filling a gap provided by the tectonics, but rather forced its way through the crust. It is still uncertain if this would have translated into surface uplift. The final architecture of the pre-Caledonian margin of Baltica when the Iapetus Ocean was formed was relatively complex. It was a wide margin that had strong lateral geometric and compositional variations, both along and across strike, such as a microcontinent and magma-poor and magma-rich domains separated by a 200 kilometer wide transition zone. These complexities partly controlled the build-up of the Scandinavian Caledonides when Baltica and Laurentia collided in the Silurian, through reactivation of riftinherited structures. Today it can be shown that variations in nappes at the same tectonostratigraphic position reflect lateral changes along the pre-Caledonian margin of Baltica.en_US
dc.language.isoenen_US
dc.relation.haspartArticle (Chapter) 1: Timing of break-up and thermal evolution of a pre-Caledonian Neoproterozoic exhumed magma-rich rifted margin. Hans Jørgen Kjøll, Torgeir B. Andersen, Fernando Corfu, Loic Labrousse, Christian Tegner, Mohamed Mansour Abdelmalak, Sverre Planke. This manuscript has been published in Tectonics, 2019. DOI: 10.1029/2018TC005375. The article is included in the thesis. Also available at: https://doi.org/10.1029/2018TC005375
dc.relation.haspartArticle (Chapter) 2: Emplacement mechanisms of a dyke swarm across the Brittle-Ductile transition and the geodynamic implications for magma-rich margins. Hans Jørgen Kjøll, Olivier Galland, Loic Labrousse, Torgeir B. Andersen. This manuscript has been published in Earth and Planetary Science Letters, 2019. DOI: 10.1016/j.epsl.2019.04.016. The article is included in the thesis. Also available at: https://doi.org/10.1016/j.epsl.2019.04.016
dc.relation.haspartArticle (Chapter) 3: A Mantle Plume Origin for the Scandinavian Dyke Complex: A “Piercing Point” for 615 Ma Plate Reconstruction of Baltica? Christian Tegner, Torgeir B. Andersen, Hans Jørgen Kjøll, Eric Brown, Graham Hagen-Peter, Fernando Corfu, Sverre Planke, Trond Torsvik. This manuscript has been published in Geochemistry, Geophysics, Geosystems, 2019. DOI: 10.1029/2018GC007941. The article is included in the thesis. Also available at: http://urn.nb.no/URN:NBN:no-70487
dc.relation.haspartArticle (Chapter) 4: A review and reinterpretation of the architecture of the South and South-Central Scandinavian Caledonides—A magma-poor to magmarich transition and the significance of the reactivation of rift inherited structures. Johannes Jakob, Torgeir B. Andersen, Hans Jørgen Kjøll. This paper has been published in Earth Science Reviews, 2019. DOI: 10.1016/j.earscirev.2019.01.004. The article is included in the thesis. Also available at: https://doi.org/10.1016/j.earscirev.2019.01.004
dc.relation.haspartArticle (Chapter) 5: Cryogenian-Ediacaran basin evolution on the incipient Iapetus margin – New discovery of a glaciogenic deposit and stromatolites. Hans Jørgen Kjøll. Manuscript is currently (April 30th, 2019) in review at Norwegian Journal of Geology. The paper is not available in DUO awaiting publishing.
dc.relation.urihttps://doi.org/10.1029/2018TC005375
dc.relation.urihttps://doi.org/10.1016/j.epsl.2019.04.016
dc.relation.urihttp://urn.nb.no/URN:NBN:no-70487
dc.relation.urihttps://doi.org/10.1016/j.earscirev.2019.01.004
dc.titleNeoproterozoic to Lower Paleozoic Evolution of the Pre-Caledonian Magma-Rich Margin of Balticaen_US
dc.typeDoctoral thesisen_US
dc.creator.authorKjøll, Hans Jørgen
dc.identifier.urnURN:NBN:no-73455
dc.type.documentDoktoravhandlingen_US
dc.identifier.fulltextFulltext https://www.duo.uio.no/bitstream/handle/10852/70340/1/PhD-Kjoell-2019.pdf


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