Search results
Results from the WOW.Com Content Network
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.
For instance, the small calcite crystals in the sedimentary rocks limestone and chalk change into larger crystals in the metamorphic rock marble. [13] In metamorphosed sandstone , recrystallization of the original quartz sand grains results in very compact quartzite , also known as metaquartzite, in which the often larger quartz crystals are ...
Porphyroblasts are often confused with porphyroclasts, which can also be large outstanding crystals, but which are older than the matrix of the rock [citation needed]. If a porphyroblastic mineral has small inclusions of minerals within it, the mineral is described as poikiloblastic. This observation can help interpret deformation history.
For instance, the small calcite crystals in the sedimentary rock limestone and chalk change into larger crystals in the metamorphic rock marble. [12] In metamorphosed sandstone, recrystallization of the original quartz sand grains results in very compact quartzite, also known as metaquartzite, in which the often larger quartz crystals are ...
Diorite – Igneous rock type Napoleonite, also known as corsite – Variety of diorite with orbicular structure; Dunite – Ultramafic and ultrabasic rock from Earth's mantle which is made of the mineral olivine; Essexite – Igneous rock type; Foidolite – Igneous rock rich in feldspathoid minerals; Gabbro – Coarse-grained mafic intrusive rock
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.
As it moves, it cools and various rock types will form through a process known as fractional crystallisation. Igneous rocks can be seen at mid-ocean ridges, areas of island arc volcanism or in intra-plate hotspots. Metamorphic rocks once existed as igneous or sedimentary rocks, but have been subjected to varying degrees of pressure and heat ...
Neomorphism is considered aggrading when recrystallization results in an any increase in crystal size. The crystal mosaics of the original mineral or crystal formation(s) often experience deterioration in the process and are eventually replaced with either crude crystalline mosaics or polymorphs. Both the resultant crystalline mosaics and/or ...