Using melt inclusions for understanding crustal melting processes

Article By:

Cesare, Bernardo Dipartimento di Geoscienze, Università di Padova, Padova, Italy.

Acosta-Vigil, Antonio Consejo Superior de Investigaciones Científicas, Instituto Andaluz de Ciencias de la Tierra, Granada, Spain.

Last reviewed:2011

DOI:https://doi.org/10.1036/1097-8542.YB110133

The Earth's continental crust may start to melt when its temperature exceeds about 650°C. This process, called anatexis, occurs in anomalously hot areas of the crust, such as young orogenic belts or continental rifts. By producing a melt of broadly granitic composition and a silica-poor, mafic solid residue, crustal anatexis is of paramount importance in shaping the continental lithosphere. On the one hand, it determines the geochemical layering (differentiation) of the crust; on the other, it allows—by the lubricating and weakening effects of the melt—much easier and faster deformation of the crust, with important tectonic and geodynamic implications. Just as for any other geological process occurring in an inaccessible area of the Earth, several aspects of crustal melting are still poorly understood by scientists, whose studies are mostly focused on either the experimental reproduction of anatexis in the laboratory or the characterization of the most common natural products of crustal melting: migmatites. Migmatite is a rock that has partially melted. It often consists of two parts: a clear leucosome, representing the crystallized melt, and a dark melanosome, representing the residual, solid material. One major unknown is the composition of the natural melts produced during anatexis, as both leucosomes in migmatites and allochthonous crustal granites appear to have been modified and/or contaminated to variable degrees after the melts have formed.

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