Migmatite

As migmatite (or Anatexit ) is called a partially molten, coarse gemengtes, metamorphic rock. The process of fusion is called anatexis. Migmatites are sometimes referred to as mixed gneisses, because they partially have the characteristics of a metamorphic rock and partly of an igneous rock. Migmatites often have a banded appearance.

Breakdown structure

After Mehnert (1968 ) migmatites are distinguished by four structural elements:

• The Paläosom is that portion of a Migmatits who did not undergo partial melting and thus includes the genetically older solid -phase of the rock. Nevertheless, the Paläosom during the melting with the molten rock may react chemically. Unlike the mobile melt the Paläosom is local. Its composition and its structure testify to the highly metamorphic parent rock, which was present prior to anatexis.
• As Neosom refers to the formerly liquid, molten phase of the rock, so the younger formation. Is this Neosom rich in quartz and feldspar, plagioclase and alkali feldspar, for example, and thus of light (usually red ) color, it is called Leukosom. The Leukosom shows an igneous texture.
• Does it have a dark color and is so rich in cordierite, biotite and hornblende, it is called melanosomes. These percentages usually form a dark border around the Leukosom. Since this is the melanosome to the refractory remnant of the parent material is from which the Leukosom has leaked, it is also called Restit.

Distinctions according to metamorphic grade

Only partially melted Migmatite be referred to as Metatexite. These are rocks whose Neosom Shares aplitischen, pegmatitic or leukogranitischen type are.

In the further increase, almost completely melted migmatites, which shall last nearly as magmatic already, but still show a low Einregelung, hot Diatexite.

As Syntexis is called the anatexis of different parent rocks.

Occurrence and incidence

The occurrence of migmatites, granitic composition indicates minimum temperatures of metamorphism of 650 ° C. Alkaline rocks melt generally at higher temperatures.

Typical is their occurrence in highly metamorphosed areas of basement areas with older, at least Proterozoic rocks. For Europe to be mentioned as outstanding references of the Baltic Shield and the Moldanubian.

In Central Europe, migmatites occur in the Black Forest before (especially in the candelabra and the Schauinsland ), in the Upper Palatinate Forest and the Bavarian Forest. In the Alps there are migmatites, for example, in Ticino ( in Simano - ceiling briefly north of Insubric seam) and in the Oetztal - Stubai -crystallin.

Types of natural stone

• Paradiso (India, Tamil )
• Brasil Tropical (Brazil, Minas Gerais )
• Multicolor Red (India)
• Aurora Borealis (Norway, Finland)