Upper Mantle Convection and Formation of Geological Structures of the Arctic

Leopold Lobkovsky

Upper mantle convection and formation of geological structures of the Arctic L.I. Lobkovsky, Institute of Oceanology RAS, [email protected] E.V. Shipilov, Polar Geophysical Institute RAS, [email protected] The seismic tomographic and paleomagnetic data taken together with plate tectonic reconstructions lead to the following geodynamic model of mantle convection. The geodynamic model of the upper mantle convection related to the global Pacific subductionrelated conveyor can be regarded as a common mechanism that controls the Mesozoic and Cenozoic tectonic evolution of the Arctic. In this regard, we present a series of reconstructions of the Arctic Region for the Mesozoic and Cenozoic based on the currently available geological and geophysical data and the previously developed geodynamic concept of the evolution of the Arctic lithosphere. As follows from these reconstructions, the Mesozoic–Cenozoic evolution of the Arctic Region comprises three main stages. The first stage lasted from the Late Jurassic to the Aptian and was related to the break off of the Chukotka and North Alaska continental blocks as elements of the ancient Arctida continent from the North American Plate; their migration in the southern direction toward the subduction zones of the South Anyui ocean and the Pacific Ocean; and collision of the Chukotka Block with the Eurasian margin during closure of the South Anyui ocean. The CA Basin with oceanic crust was formed by diffuse spreading. The second stage from the Aptian–Albian to the Late Cretaceous was characterized by continental rifting due to near latitudinal extension of the Central Arctic fragment of the ancient Arctida continent and by formation of the system of rises and deeps (Lomonosov Ridge, Alpha–Mendeleev Rise, and the Makarov and Podvodnikov basins). Rifting was accompanied by within magmatism, which expanded its area from Spitsbergen and Franz Josef Land to the northern CA Basin. The third stage of the evolution, which began in the Paleocene, is characterized by slow spreading in the Gakkel Ridge. As a result, the previously formed Lomonosov Ridge along with the central fragment of the Arctida continent (both belonging to the Amerasia Subplate, which formed in the Cretaceous) broke away from the Barents–Kara margin toward Alaska and the Aleutian subduction zone, having freed a space for the oceanic Eurasia Basin. Thus, the analysis of the geological evolution has shown that the Lomonosov Ridge and Alpha–Mendeleev Rise combined with the Makarov and Podvodnikov basins are the fragments of the ancient Arctida continent, which make up a tectonic bridge that has retained its tectonic connection with the continental margins of Eurasia and North America, at least, since the Cretaceous time. Therefore these elements are natural components of these continental margins. References Laverov N. P., Lobkovsky L. I., Dobretsov N. L., Vernikovsky V. A., Sokolov S. D., E. V. Shipilov, 2013,. Geotectonics, 47, 1, 3–33.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013