Physical modeling of the formation conditions of microcontinents and continental marginal plateaus

Resumo

The geodynamical conditions allowing formation of microcontinents or blocks of continental crust that are not completely detached from the parent continent are considered. These blocks can be preserved in the form of islands emerging above sea level or exist as submerged plateaus located within the continental margins, depending on the thermomechanical conditions of continental rifting. Physical modeling has shown that formation of microcontinents or partially detached continental microblocks is constrained by the following key conditions: presence of rift segments that are offset relative to each other and are propagating toward each other; formation of oceanic crust along at least one or two rift segment; for a microcontinent, it is the presence of a hot spot, which weakens the lithospheric strength and thus facilitates the jump of the spreading axis from one rift segment to another due to which the continental microblock can become completely detached from the parent continental plate. During the evolution, microblocks undergo rotational deformations in both the horizontal and vertical planes also leading to the local jumps of the spreading axes and the formation of an asymmetric rift.