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Foliation in geology refers to repetitive layering in metamorphic rocks. [1] Each layer can be as thin as a sheet of paper, or over a meter in thickness. [ 1 ] The word comes from the Latin folium , meaning "leaf", and refers to the sheet-like planar structure. [ 1 ]
Flow banding is a geological term to describe bands or layers that can sometimes be seen in rock that formed from magma (molten rock). [ 1 ] Flow banding is caused by friction of the viscous magma that is in contact with a solid rock interface, usually the wall rock to an intrusive chamber or, if the magma is erupted, the surface of the Earth ...
If the heat is too intense, foliation will be weakened due to the nucleation and growth of new randomly oriented crystals and the rock will become a hornfels. [1] If minimal heat is applied to a rock with a preexisting foliation and without a change in mineral assemblage, the cleavage will be strengthened by growth of micas parallel to foliation.
2-dimensional section of Reeb foliation 3-dimensional model of Reeb foliation. In mathematics (differential geometry), a foliation is an equivalence relation on an n-manifold, the equivalence classes being connected, injectively immersed submanifolds, all of the same dimension p, modeled on the decomposition of the real coordinate space R n into the cosets x + R p of the standardly embedded ...
In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct cleavage. In other words, it is a metamorphic rock composed of mineral grains easily seen with the unaided eye, which form obvious compositional layers ...
The white minerals are plagioclase; the light grey ones are quartz; the dark, greenish ones are biotite and hornblende, which developed foliation. Archean TTG rocks appear to be strongly deformed grey gneiss, showing banding, lineation, and other metamorphic structures, whose protoliths were intrusive rocks. [4]
Ptygmatic folds are formed by highly plastic ductile deformation of the gneissic banding, and thus have little or no relationship to a defined foliation, unlike most regular folds. Ptygmatic folds can occur restricted to compositional zones of the migmatite, for instance in fine-grained shale protoliths versus in coarse granoblastic sandy ...
foliation The parallel alignment of textural and structural features of a rock. fossil Any mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, or other once-living organisms. fossiliferous Bearing or being composed of fossils in rocks or strata. fossilization fracture Any crack or discontinuity.