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Dislocation creep is a non-linear (plastic) deformation mechanism in which vacancies in the crystal glide and climb past obstruction sites within the crystal lattice. [1] These migrations within the crystal lattice can occur in one or more directions and are triggered by the effects of increased differential stress.
Little is known about the history of the oldest exposed rocks in the area due to extensive metamorphism.This somber, gray, almost featureless crystalline complex is composed of originally sedimentary and igneous rocks with large quantities of quartz and feldspar mixed in. [1] The original rocks were transformed to contorted schist and gneiss, making their original parentage almost unrecognizable.
Because rocks are essentially aggregates of minerals, we can think of them as poly-crystalline materials. Dislocations are a type of crystallographic defect which consists of an extra or missing half plane of atoms in the periodic array of atoms that make up a crystal lattice.
Both the resultant crystalline mosaics and/or polymorphs are chemically identical—with a few minor exceptions due to certain relatively minute chemical alterations that occur during the reaction processes—to the minerals from which the aggraded crystals developed. [4] One common form of aggrading neomorphism is called porphyroid neomorphism.
Specifically in sedimentology, a bed can be defined in one of two major ways. [2] First, Campbell [3] and Reineck and Singh [4] use the term bed to refer to a thickness-independent layer comprising a coherent layer of sedimentary rock, sediment, or pyroclastic material bounded above and below by surfaces known as bedding planes.
Layers of rock that fold into a hinge need to accommodate large deformations in the hinge zone. This results in voids between the layers. These voids, and especially the fact that the water pressure is lower in the voids than outside of them, act as triggers for the deposition of minerals.
The degree of deformation and metamorphism along with rock type determines the kind of cleavage feature that develops. Generally, these structures are formed in fine grained rocks composed of minerals affected by pressure solution. [1] Cleavage is a type of rock foliation, a fabric element that describes the way planar features develop in a ...
Melt production and accretion of melt onto continental crust in a subduction zone [1]. A subduction zone is a region of the Earth's crust where one tectonic plate moves under another tectonic plate; oceanic crust gets recycled back into the mantle and continental crust gets produced by the formation of arc magmas.