From a collage of microplates to stable continental crust - an example from Precambrian Europe

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dc.contributor University of Helsinki, Department of Geosciences and Geography en
dc.contributor.author Korja, Annakaisa
dc.date.accessioned 2014-10-18T21:12:16Z
dc.date.available 2014-10-18T21:12:16Z
dc.date.issued 2013
dc.identifier.citation Korja , A 2013 , ' From a collage of microplates to stable continental crust - an example from Precambrian Europe ' , Geophysical Research Abstracts , vol. 15 , EGU2013-9975 . < http://meetingorganizer.copernicus.org/EGU2013/EGU2013-9975.pdf > en
dc.identifier.issn 1029-7006
dc.identifier.other PURE: 40929732
dc.identifier.other PURE UUID: 210217c6-6ea1-42ac-a6da-535437cafb47
dc.identifier.other ORCID: /0000-0001-8940-9248/work/29390774
dc.identifier.uri http://hdl.handle.net/10138/136263
dc.description.abstract Svecofennian orogen (2.0-1.7 Ga) comprises the oldest undispersed orogenic belt on Baltica and Eurasian plate. Svecofennian orogenic belt evolved from a series of short-lived terrane accretions around Baltica’s Archean nucleus during the formation of the Precambrian Nuna supercontinent. Geological and geophysical datasets indicate W-SW growth of Baltica with NE-ward dipping subduction zones. The data suggest a long-lived retreating subduction system in the southwestern parts whereas in the northern and central parts the northeasterly transport of continental fragments or microplates towards the continental nucleus is also documented. The geotectonic environment resembles that of the early stages of the Alpine-Himalayan or Indonesian orogenic system, in which dispersed continental fragments, arcs and microplates have been attached to the Eurasian plate margin. Thus the Svecofennian orogeny can be viewed as proxy for the initial stages of an internal orogenic system. Svecofennian orogeny is a Paleoproterozoic analogue of an evolved orogenic system where terrane accretion is followed by lateral spreading or collapse induced by change in the plate architecture. The exposed parts are composed of granitoid intrusions as well as highly deformed supracrustal units. Supracrustal rocks have been metamorphosed in LP-HT conditions in either paleo-lower-upper crust or paleo-upper-middle crust. Large scale seismic reflection profiles (BABEL and FIRE) across Baltica image the crust as a collage of terranes suggesting that the bedrock has been formed and thickened in sequential accretions. The profiles also image three fold layering of the thickened crust (>55 km) to transect old terrane boundaries, suggesting that the over-thickened bedrock structures have been rearranged in post-collisional spreading and/or collapse processes. The middle crust displays typical large scale flow structures: herringbone and anticlinal ramps, rooted onto large scale listric surfaces also suggestive of spreading. Close to the original ocean-continent plate boundary, in the core of the Svecofennian orogen, the thickened accretionary crust carries pervasive stretching lineations at surface and seismic vp-velocity anisotropy in the crust. The direction of spreading and crustal flow seems to be diverted by shapes of the pre-existing boundaries. It is concluded that lateral spreading and midcrustal flow not only rearrange the bedrock architecture but also stabilize the young accreted continental crust in emerging internal orogenic systems. Pre-existing microplate/ terrane boundaries will affect the final architecture of the orogenic belt. en
dc.format.extent 1
dc.language.iso eng
dc.relation.ispartof Geophysical Research Abstracts
dc.relation.uri http://meetingorganizer.copernicus.org/EGU2013/EGU2013-9975.pdf
dc.rights en
dc.subject 1171 Geosciences en
dc.title From a collage of microplates to stable continental crust - an example from Precambrian Europe en
dc.type Conference article
dc.type.uri info:eu-repo/semantics/other
dc.contributor.pbl

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