Neotectonics and Mantle Earthquakes in the Pamir-Hindu Kush Region

摘要

Tectonic aspects of the formation of the Pamirs-Hindu Kush zone of intermediate earthquakes are discussed. A model of the regional late-collision (neoteclonic) evolution is developed based on the analysis of geologic data. The first stage of this evolution spans from the late Eocene to the beginning of the late Miocene; the second stage, from the late Miocene to the Holocene. These stages are characterized by different thermody-namic conditions and, correspondingly, by different geodynamic settings that determined a specific style of tectonic deformation. The early stage was marked by differentiated lateral displacements of the Earth's tectoni-cally delaminated crust. The heating of the crust that is reflected in intense granitic magmatism promoted delaminalion. At the late stage, the heating and delamination probably waned and were replaced by more homogeneous lateral motion of blocks and by regional uplift. Because of lateral displacements, the oceanic crust fragments of different age were overridden by blocks of the continental crust and submerged to a depth of 40-70 km. Their eclogitization might have lead to further submergence into the mantle. Mantle earthquakes in the Pamir-Hindu Kush zone are induced by relaxation of the stress that accumulates in submerging fragments.