Anatexie

The anatexie is fusion partial of the rocks in the Earth's crust.

Process

The metamorphic rocks can be hidden in conditions of sufficient temperature and pressure to initiate the fusion of part of constituent minerals. The term comes from the Greek anatêksis , “fusion”.

The partially molten rock is transformed into Migmatite. It is a rock in which the products separated from the Fusion, the refractory leucosomes, and minerals, which did not melt and form the mélanosome, also called mésosome. Compound gneisses, also called Anatexite S, are frequent in the zones of root of the eroded mountains.

If fusion is more important, even total, the products of partial fusion can gather to form a magma and, if this one is of granitic nature (for example if the partially molten rock is a pelitic Sédiment) one will obtain a granite of anatexie after cooling.

The beginning of fusion depends on many factors, in particular on the chimism of the involved rocks, the total pressure, and finally of the presence and the quantity of steam (PF drops).

The order of fusion of the rocks is, in theory, the reverse about split crystallization and of the reactional continuations.

The destiny of the formed liquid can be varied:

it remains with the solid residues (nonmolten): there is formation of compound gneisses or anatexites
it can, in certain cases, to separate from the nonmolten residue, but one needs a great relative quantity of magma (1/3)
it separates completely from the residues and migrates upwards, is injected in " diapirs" in the wall-rocks denser, but “does not digest them” not while passing. Its chemistry thus does not change.

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