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Magmatism and formation of a wide continent-ocean transition at the East Greenland margin, Euromargins 2003 OBS Experiment

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Voss, M. and Jokat, W. (2006): Magmatism and formation of a wide continent-ocean transition at the East Greenland margin, Euromargins 2003 OBS Experiment , ESF Euromargins Workshop, 4-7 Oct., Bologna, Italy. .
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Abstract:

Deep seismic refraction data were gathered along the East Greenland rifted margin north of the Jan Mayen Fracture Zone in 2003 in the framework of the EUROMARGINS project. Investigations of the deep structure of the continental margin, and comparison with the conjugate margin off Norway, provide key constraints on margin's formation and structural evolution during and after Late Cretaceous - Early Tertiary rifting and continental break-up.Most of the four acquired transects were located between 72°N and 76°N on the prolongation of fjord profiles acquired during earlier investigations. In the Godthåb Gulf and the Kejser Franz Joseph Fjord, forward travel-time modelling of ocean bottom seismometer (OBS) data established regional velocity models of the continental margins and the transition to oceanic crust. Along both profiles, a wide continent-ocean transition zone appears with lateral and vertical velocity variations. Furthermore, both profiles show a lower crustal body with p-wave velocities of 7.1 7.4 km/s which is interpreted as underplated magmatic material. It extends across distances of 140 km to 190 km, respectively. Wide angle reflections show a well constrained Moho as well as an intermittent top reflector (T) of the high velocity body.The thickness of the lower crustal body varies by up to 15 km. From earlier investigations, a southward decrease in the amount of underplated material at the COT is observable; near Kong Oscar Fjord the underplating is thinner than in our profiles, and near Scoresby Sund no underplating was identified. The existence of voluminous underplating is direct evidence of rift-related magmatism that wasnt extruded like the adjacent flood basalts. Compared to the conjugate Vøring Margin off Norway, differences in the crustal thickness and degree of magmatic underplating are evidence for different rift formation processes.

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