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eclogitization
Eclogitization is the tectonic process in which the appearance of high-pressure, metamorphic facies, eclogite leads to an increase in crustal densities. These crustal density changes lead to a change in plate kinematics, and plate motion of subduction zones. There is the argument that collision between two continents should slow down because of continental buoyancy. For convergence to continue, it should do so at a new subduction zone where oceanic crust can be consumed.〔 Certain areas such as the Alps, Zagros, and Himalayas have led geologists to propose a ''continental undertow'' that continues subduction. This ''continental undertow'' is explained by the slab pull concept. Slab pull is the concept that plate motion is driven by the weight of cool, dense plates and that heavier plates will begin to subduct. Once a descending slab is disconnected there must be a force that continues subduction. Eclogitization is the mechanism for continuing subduction after slab detachment in a subduction zone.〔
==Geologic setting and effect of eclogitization==
Eclogitization typically occurs at two locations in a collisional orogen (fig 2), in the subduction of crust and at the base of the crustal root of the overriding crust. At these zones high pressures are reached as well as medium to high temperatures and eclogitization commences. Metamorphic re-crystallization during burial can lead to a significant density increase (up to 10% in the case of eclogitization) meaning, approximately 300–600 kg/m3 of crustal rocks and continental lower crust and oceanic crust reach higher density than the mantle.
This density increase acts as the main driver in the convection of Earth's mantle. It also explains the disconnection of a tectonic unit from the descending lithosphere, subsequent continuation of subduction, and the exhumation following subduction.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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