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| Titel |
The formation of the North Barents Superdeep Basin by gabbro to eclogite
transformation in continental crust |
| VerfasserIn |
Eugene Artyushkov, Peter Chekhovich |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141927
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| Publikation (Nr.) |
 EGU/EGU2017-5486.pdf |
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| Zusammenfassung |
| Arctic area includes deep basins both water loaded and sediment loaded ones. They are
underlain by the attenuated crystalline crust with high P-wave velocities. The nature of the
crust in these basins and mechanisms of their formation are debatable. Detailed data on the
North Barents superdeep sedimentary Basin can be used to approach the problem. To produce
such a basin with 16-18 km of sediments by stretching of continental lithosphere
the beta factor should be about 2.5. According to the seismic reflection profiling
data the intensity of stretching of the crystalline basement in the basin does not
exceed 10%. This could ensure the sediment loaded subsidence of no more than 1
km.
In the deepest part of the basin the crystalline crust is only 14 km thick and has the mean
density of 2900 kg/m3 typical of the oceanic crust. Subsidence of oceanic crust formed at the
axis of spreading continues 80 Myr at a rate rapidly decreasing in time. In the North Barents
Basin intense subsidence continued 220 Myr since the Late Devonian and until the
Late Jurassic. Moreover, about two thirds of the subsidence took place since the
beginning of the Triassic while subsidence of oceanic crust would have already ended
long ago. These data make rather improbable the existence of oceanic crust in the
basin.
The analysis of the seismic refraction profiling data shows that the basin is several
kilometers deeper than it would be if the Moho boundary was underlain by mantle
peridotites. No large negative isostatic anomalies are however observed above the basin.
Abnormally large depth of the basin can be explained by the existence under the
Moho of a layer of eclogites 15-20 km thick. These mafic rocks which are denser
than mantle peridotites pertain to the crust by their composition. Together with
crystalline rocks 14 km thick located above the Moho they form the crystalline
crust with the thickness 30-35 km which is typical of many continental regions.
The formation of eclogites from gabbro in the lower crust was the main cause of
crustal subsidence in the North Barents Basin. The seismic tomography data show
that the basin is underlain by a thick lithospheric layer typical of the Precambrian
cratons.
According to the seismic and gravity data thick layers of eclogites exist under the Moho
boundary in some other deep basins. Among them are the deep-water Gulf of Mexico, the
North Caspian and South Caspian Basins, 20 km deep, the North Chukchi superdeep Basin
filled with 18 km of sediments and the deep-water basin on the Mendeleev High. According
to this feature all these basins are underlain by thick continental crust and their
formation was the result of the gabbro to eclogite transformation in the lower crust. |
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