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Discrete Dynamics in Nature and Society
Volume 6 (2001), Issue 4, Pages 281-290
http://dx.doi.org/10.1155/S1026022601000322

Accelerated non-linear destruction of the earth's crust

United Institute of Physics of the Earth, B. Gruzinskaya 10, Moscow 123810, Russia

Received 3 January 2001

Copyright © 2001 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The upper part of the Earth—the lithospheric layer, 100 km thick, is rigid. Segments of this spherical shell–lithospheric plates are drifting over a ductile asthenosphere. On the continents, the lithosphere includes the Earth's crust, 40 km thick, which is underlain by peridotitic rocks of the mantle. In most areas, at depths 20–40 km the continental crust is composed of basalts with density 2900kg m3. At temperature and pressure typical for this depth, basalts are metastable and should transform into another assemblage of minerals which corresponds to garnet granulites and eclogites with higher densities 3300–3600 kg m3. The rate of this transformation is extremely low in dry rocks, and the associated contraction of basalts evolves during the time 108 a. To restore the Archimede's equilibrium, the crust subsides with a formation of sedimentary basins, up to 10–15 km deep.

Volumes of hot mantle with a water-containing fluid emerge sometimes from a deep mantle to the base of the lithosphere. Fluids infiltrate into the crust through the mantle part of the lithosphere. They catalyze the reaction in the lower crust which results in rock contraction with a formation of deep water basins at the surface during 106 a. The major hydrocarbon basins of the world were formed in this way. Infiltration of fluids strongly reduces the viscosity of the lithosphere, which is evidenced by narrow-wavelength deformations of this layer. At times of softening of the mantle part of the lithosphere, it becomes convectively replaced by a hotter and lighter asthenosphere. This process has resulted in the formation of many mountain ranges and high plateaus during the last several millions of years. Softening of the whole lithospheric layer which is rigid under normal conditions allows its strong compressive and tensile deformations. At the epochs of compression, a large portion of dense eclogites that were formed from basalts in the lower crust sink deeply into the mantle. In some cases they carry down lighter blocks of granites and sedimentary rocks of the upper crust which delaminate from eclogitic blocks and emerge back to the crust. Such blocks of upper crustal rocks include diamonds and other minerals which were formed at a depth of 100–150 km.