The Formation of the North Chukchi and East Barents Super-Deep Basins from the Gabbro to Eclogite Transformation in the Lower Continental Crust
Eugene V. Artyushkov
Institute of Physics of the Earth, Moscow, Russia.
These two basins, up to ~ 20 km deep, are commonly supposed to be underlain by the oceanic crust, 10-15 km thick. The subsidence of oceanic crust formed in the spreading ridges proceeds for ~ 80 Ma. In the North Chukchi and East Barents basins, the major part of the sediments was formed ≥ 100 Ma after the start of the subsidence. The sediment thickness is almost twice as large in them as that necessary to fill the basins on the oceanic crust. These basin features are incompatible with the occurrence of oceanic crust in the basins and indicate that they are underlain by the continental crust. In a state of isostasy, to keep the consolidated crust, 10-15 km thick, at a depth of ~ 20 km, a layer of dense eclogites, ~ 20-25 km thick, should be located under the Moho boundary. These mafic rocks are characterized by high P-wave velocities which are also typical of mantle peridotites. However, by their composition they belong to the crust. Hence the thickness of the consolidated crust in the basins is of ~ 30-40 km which is typical of continental cratonic areas. No intense stretching occurred in the North Chukchi and East Barents basins. Under such circumstances, the crustal subsidence can be explained by the transformation of gabbro in the lower crust into eclogites. At several epochs, strong acceleration of the subsidence occurred in the basins. This was caused by an increase in the rate of metamorphism in the lower crust due to infiltration of active fluids from small mantle plumes. Rapid crustal subsidence is a typical feature of large hydrocarbon basins. This took also place in the West Siberian, North and South Caspian basins, in the Volga-Urals, Timan-Pechora, and many other hydrocarbon basins. The rapid subsidence in the North Chukchi basin indicates that similar to these basins and the East Barents one, it may also have very large hydrocarbon resources.
AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia