On the motion of lithospheric plates in the oceans and transition zones

Abstract

The formation; horizontal displacement and immersion of lithospheric plates; corresponding to the plate tectonics hypothesis; are considered. It is shown that the magmatism of the mid-oceanic ridges does not correspond to the volume of the crust of plates and the magmatism of the transition zones from the continents to the oceans. When plates move to the continents 70 % do not submerge. Another 7 % of the length of the transition zones is the depth of hypocenters of earthquakes of 20 ± 20 km (transitional zones of the Colombian type). Seismicity on the continents near the “passive” eastern margins of North America and Africa; the western and southern margins of Australia; the western edge of Eurasia is less intense; but in principle not different from the “ñolombian”. Approximately 2 % of the length of the transition zones are earthquakes with depths of foci up to 70—100 km. About 14 % occupy zones with depths of hypocenters to 250—450 km; 7 % of the length of the boundaries of the continents and oceans are represented by the deepest foci (450—700 km). Thus; the total focal regions (and; consequently; the subduction zones) are not the rule; but the exception. The geological and geophysical data do not correspond to the scheme by which the edge of the slab is compacted before the trench due to cooling. Plate dipping is unrealistic due to its low density and large mantle resistance under the trough. The location of earthquakes’ hypocenters under a trough and an island arc does not agree with subduction. It is impossible to ex-plain the immersion of a plate by compacting its crustal part during the polymorphic transformation of pyroxenes into garnets. The analysis of the energy of subduction process was carried out using the data on the parameters of the earthquake foci. It is showed that for a process according to the plate tectonics scheme; a power source is 1000 times more powerful than the actual ones. The obtained results allow us to consider the hypothesis of subduction of lithospheric plates unrealistic. An alternative scheme for the formation of focal zones is given.