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Lower crustal seismic velocities from Lofoten-Vesterålen, North Norway

Authors
Journal
Tectonophysics
0040-1951
Publisher
Elsevier
Publication Date
Volume
157
Issue
4
Identifiers
DOI: 10.1016/0040-1951(89)90143-1
Disciplines
  • Earth Science

Abstract

Abstract The archipelago of Lofoten-Vesterålen comprises Archaean and Proterozoic rocks in granulite or amphibolite facies. The area is characterised by a large gravity anomaly (+120 mGal) and thin crust (c. 25 km) and it has been suggested that it represents a deep section into the continental crust. Compressional and shear wave velocities have been measured in the laboratory on over 70 samples from the area, most of them to 0.4 GPa confining pressure. Velocity profiles are then deduced for sections of the crust assuming a restored horizontal Moho and it is shown that “upper” and “lower” crustal divisions of approximately 5.9–6.2 km s −1 and 6.5–6.6 km s −1 can be recognised, which are similar to those found on seismic refraction lines in Scandinavia. The velocities of the Lofoten granulites are, however, higher than the velocities observed on the Lofoten seismic refraction experiment. Possible reasons for this, including the opening of cracks at low pressure, retrograde metamorphism, the interpretation of the refraction data, or major tectonic dislocation, are explored.

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