Migmatite

Classification：Metamorphic Rock

It consists of two parts: light granite and dark metamorphic rock. Mineral composition and structure are often uneven.

In some areas of high-grade metamorphism, when the temperature is high enough, the material is partially melted, that is, deep melting, resulting in liquid which is usually composed of granites. If these liquids are kept closed and crystallized in their rock mass to produce mixed rocks or Migmatite, this process is called Migmatite, which belongs to the category of metamorphism and is the type of metamorphism transition to magmatism, which determines that Migmatite has geology between metamorphic and magmatic rocks. The characteristics of science and petrology.

Migmatite is formed by Migmatite (the type of metamorphism transition to magmatism) and consists of two basic components, the matrix (substrate) and the vein body (vein material). The matrix is amphibolite or granulite phase change rock, representing mixed primitive rock, more or less reformed, also known as paleosome, vein body is a long British substance or granitic substance, representing the new part of the middle Migmatite, and also called the new formation (neosome). [1]
There are various forms of Migmatite, and the changes in composition, structure and structure are also large. It indicates that the formation conditions of Migmatite are complex and diverse.

Geological characteristics:
The large area of Migmatite is distributed in the Precambrian shield area and the Phanerozoic island arc zone, the large collision zone and the continental extensional belt low middle P/T region metamorphic zone, which symbiotic and intertransition with the middle and advanced metamorphic rocks and the granitoid deep intrusive bodies. It usually does not appear in the subduction zone.
Migmatite also occurs in the contact halos of granite intrusions, and is associated with intermediate and high-grade contact metamorphic rocks. It is usually distributed in the contact halo, and Migmatite, which is symbiotic with the middle and high contact metamorphic rocks, is called the marginal Migmatite, and is distributed in the regional metamorphic zone, and the Migmatite in the middle and high regional metamorphic rocks is called the regional Migmatite.

Petrological characteristics:

Basic composition:
Generally speaking, Migmatite is made up of two basic components: dark matrix and light colored veins. The matrix is amphibolite or granulite facies metamorphic rocks, representing the original rock Migmatite, but influenced by the transformation. Veins are felsic or granitic substances, representing the new part of Migmatite.
Mehnert (1968) called the two basic components of Migmatite as palaeontology and new body. He noticed that the veins and bodies usually formed by dark mineral aggregates were called dark bodies, and correspondingly the light colored part of the body was called shallow.
Chromophore:
Johannes (1983) suggested that we should describe Migmatite in terms of "light color body", "dark body" and "middle color body". [1]

Composition characteristics
Migmatite palaeospores are mostly argillaceous, felsic and intermediate high-grade metamorphic rocks, and basic metamorphic rocks are rare. Light coloured bodies are felsic, and are partly fused products of argillaceous felsic metamorphic rocks. Dark bodies, biotite and garnet are probably insoluble residues.
Under the same Migmatite conditions, the mudstone and long angled metamorphic rocks are obviously susceptible to the mixed transformation, while the calcareous and magnesia metamorphic rocks are generally not affected by the Migmatite.

Migmatite structure:
The paleomer is characterized by flakes, granitic and metasomatism, and other metasomatism and metasomatism. Neotenite and gneiss granite usually have semi crystalline granular structure and metasomatism structure, and their orientability is weaker than ancient ones. The metasomatic structure is the obvious feature of Migmatite structure. With the enhancement of Migmatite, metasomatism tends to be more developed.
The research shows that the metasomatism in Migmatite is often the structural evidence of partial melting: the metasomatic structures in the paleo formation are often partial melting structures, while the metasomatic structures of the Neo and flax like granites are often molten residual structures.

Migmatite Construction:
The way of spatial arrangement of matrix and vein determines the characteristics of Migmatite structure.
Mehnert (1968) divided the Migmatite into breccia, reticulate, clastic, fine pulse, strip, sausage like, fold, intestinal, eyeball, plaque, and so on.
The most common Migmatite consists of 4 categories: brecciform Migmatite, eyeball Migmatite, stripe Migmatite and halo stained Migmatite.
Veined Migmatite is a Migmatite with a number of nearly equal parallel light colored felsic or granitic veins. It is characterized by different thickness. Some of them are believed to belong to external injection, some of which are thought to be formed by the secretion (differentiation) of protolith (metamorphic rocks).

Breccia Migmatite refers to dark colored hornblende rocks, which are cut by irregular colored felsic or granitic veins, forming brecciated rocks of different sizes.
Reticulated Migmatite refers to Migmatite containing fuzzy light colored meshed or dendrite felsic veins.
Misty rock is also called cloud dyed rock, which means Migmatite with a nebulous appearance. It contains fine reticulate, cloudy, or filamentous long angled veins, and has a faint streak or small spot of dark color (including black mica or amphibole, etc.).

The cause of Migmatite:
So far, people's views on the formation mechanism of Migmatite can be summarized as four basic mechanisms: deep penetration, magma injection, metasomatism and metamorphism.
Both magma injection and deep melting say that the Migmatite process is considered as magma process, and there are associated granitic rocks. The metasomatism and metamorphism is divided into different Migmatite process into metamorphic process, does not need to be associated with granitic rock.