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Crustal structure of northwestern Svalbard and the adjacent Yermak Plateau: Evidence for Oligocene simple shear rifting and non-volcanic break-up.

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Ritzmann, O. and Jokat, W. (2003): Crustal structure of northwestern Svalbard and the adjacent Yermak Plateau: Evidence for Oligocene simple shear rifting and non-volcanic break-up. , Geophysical Journal International, 152 , pp. 139-159 .
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Abstract:

In 1999 new seismic refraction data were collected off northwestern Svalbard and theadjacent Yermak Plateau. A 260 km long profile provides detailed velocity informationfor the northeastern edge of the Eurasian Continent and the adjacent Yermak Plateau.North of Forlandsundet Graben the depth of the Moho varies between 23 and 28 km,and remains at this depth to the northern edge of the profile at 81°N. The crustal lithologyoff western Svalbard can be related to the basement province west of the Raudfjorden Fault Zone.Off the northern shoreline of Svalbard the structure of the Tertiary Danskoya Basin is mapped.Below this, a late Silurian/early Devonian basin, with seismic velocities between 5.1 and 5.8 km/sand a thickness of up to 8 km is present. A Paleozoic sequence of up to 6 km thickness isexpected below the Tertiary cover north of the Danskoya Basin. An earlier suggestion, thatOligocene rift processes affected the southern Yermak Plateau (Eiken, 1993), is confirmed.A detachment structure is situated below the Paleozoic Basin below Danskoya Basin, whichis likely the consequence of simple shear tectonics. The middle crust exhibits low seismicvelocities above the detachment fault. The lowermost crust beneath is slightly contaminated bymantle derived melts, which is deduced by the slightly elevated velocities of the lowermost crust.These melts can be attributed to decompressive melting caused by modest uplift of the Mohoduring stretching.The velocity-depth model provides no evidence for large magmatic activitythat implies a non-volcanic rifted margin history. This leads to the assumption that the proposedermak Hot Spot during the break-up of Svalbard from northern Greenland did not exist.

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