Geodynamic Evolution of Intra-Oceanic Island‒Arc Systems: Expansive (Izu-Bonin‒Marian), Accretionary (Nemuro‒Olutorsky) and Stationary (Aleutian) Types

Abstract

The authors propose a typification of intra-oceanic island‒arc systems according to the geodynamics of their development in the oceanic space. The currently existing and reconstructed (represented by terranes on the margins of the continents) intraoceanic island-arc systems of the late Mesozoic-Cenozoic are subdivided into expansive, accretionary, and stationary types. Systems of the expansive type (Izu-Bonin–Marian and Lesser Antilles) grow both towards the subducting oceanic plate and towards the free oceanic space – their geodynamics is determined by processes in the oceanic plates. The mantle currents under the overhanging lithospheric plate are directed towards the subducting plate. Accretionary systems such as the Olyutor–East Kamchatka, Nemuro–Lesser Kuril, and Talkitna systems have completed their development as part of active continental margins. The paleotectonic reconstruction of such systems shows that these systems in the course of their development were reduced to relict terranes, tectonically aligned with continental margins. The geodynamics of intra-ocean systems of the accretion type also depends on processes in oceanic plates, but leads to the opposite result compared to expansive systems. This is due to the direction of mantle flows under the overhanging plate, which is opposite to the expansion type, i.e. coinciding in direction with the mantle flow under the absorbed plate. The stationary Aleutian island-arc system is intercontinental and its development in space, as well as the formation of internal structures (the Paleogene island arc of the Bowers Ridge), depended on the difference in the relative movement of the Eurasian and North American lithospheric plates. The most specific feature of this system is the absence of signs of back-arc basin opening, which invariably characterizes expansive and accretionary island-arc systems. It is assumed that this specific feature of the system may be related to the mantle flow under the overhanging slab, which has a transverse direction with respect to the direction of the subducting slab. The Aleutian system, from the moment of its formation, was and remained autochthonous in relation to the North American and Eurasian continents.