Ordovician to Silurian magmatism on the Utsira High, North Sea: implications for correlations between the onshore and offshore Caledonides
A. M. Lundmark, T. Sæther, R. Sørlie, 2014. "Ordovician to Silurian magmatism on the Utsira High, North Sea: implications for correlations between the onshore and offshore Caledonides", New Perspectives on the Caledonides of Scandinavia and Related Areas, F. Corfu, D. Gasser, D. M. Chew
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The age and tectonic significance of two basement granitoids cored on the Utsira High, Viking Graben, North Sea, are constrained by zircon LA-ICPMS data. Syenite in well 25/10-2R is dated to 482±2 Ma, with ɛHf(482) values from −4.4 to −5.8, and granite in well 16/1-12 yields an age of 436±3 Ma with ɛHf(436) values from +3.7 to −0.5. The evolved Hf-signature of the syenite demonstrates 482 Ma reworking of Palaeoproterozoic–Archaean crust, interpreted to reflect Taconian–Grampian orogenesis. New and recently published data from the offshore Caledonides allow a first-order correlation of the Utsira High basement with the surrounding on- and offshore Caledonides. The Utsira High occupies a similar position with respect to Dalradian rocks as the Scottish Midland Valley terrane. Geophysical data indicate a volcanic arc beneath the East Shetland Basin, forming a northwards continuation of the Utsira High basement. We propose that the offshore volcanic arc segments represent the northeastern continuation of the Scottish Grampian orogen across the Mesozoic North Sea rift. A north-striking terrane boundary fault is proposed to separate the volcanic arc from the East Shetland Platform and merge northwards with the offshore extension of the Great Glen Fault–Møre Trøndelag Fault Complex.
U–Pb and Lu–Hf isotopic data are available at http://www.geolsoc.org.uk/SUP18705.
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New Perspectives on the Caledonides of Scandinavia and Related Areas
The Caledonides are a major orogenic belt that stretches from the Arctic, through Scandinavia, East Greenland, Britain and Ireland into the Atlantic coast of North America. Following the break-up of Rodinia, the Caledonides formed in the Palaeozoic by the drifting of various continents and their eventual aggregation in the Silurian and Devonian. The orogen subsequently fragmented during the opening of the Atlantic Ocean. This volume brings together 25 papers presenting the results of modern research that investigates the orogenic processes and the provenance of specific components of the belt. The contributions reflect different lines of research, linking traditional field studies with modern analytical techniques. In addition three overview papers summarize the main features of the belts in Scandinavia, Svalbard, East Greenland, Britain and Ireland, highlighting the advances made since the last major synthesis of the Scandinavian Caledonides 30 years ago, and discussing important open questions.