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Partial melting is the phenomenon that occurs when a rock is subjected to temperatures high enough to cause certain minerals to melt, but not all of them. Partial melting is an important part of the formation of all igneous rocks and some metamorphic rocks (e.g., migmatites), as evidenced by a multitude of geochemical, geophysical and petrological studies.
Anatexis. Anatexis (via Latin from Greek roots meaning "to melt down") is the partial melting of rocks. [1] Traditionally, anatexis is used specifically to discuss the partial melting of crustal rocks, while the generic term "partial melting" refers to the partial melting of all rocks, in both the crust and mantle. [citation needed]
Migmatite on the coast of Saaremaa, Estonia. Intricately-folded migmatite from near Geirangerfjord, Norway. Migmatite is a composite rock found in medium and high-grade metamorphic environments, commonly within Precambrian cratonic blocks. It consists of two or more constituents often layered repetitively: one layer is an older metamorphic rock ...
The magmatic aspects of plate tectonics tends to gradual segregation within or between the mantle and crust. As magma forms, the initial melt is composed of the more silicic phases that have a lower melting point. This leads to partial melting and further segregation of the lithosphere. In addition the silicic continental crust is relatively ...
Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the feldspar in the rock consisting of plagioclase. This places andesite in the basalt /andesite field of ...
Flux melting. In igneous petrology and volcanology, flux melting occurs when water and other volatile components are introduced to hot solid rock, depressing the solidus. In engineering and metallurgy, flux is a substance, such as salt, that produces a low melting point (liquidus) mixture with a metal oxide. In the same way, the addition of ...
Igneous differentiation. In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement, or eruption. The sequence of (usually increasingly silicic) magmas produced by igneous differentiation is ...
Diorite results from the partial melting of a mafic rock above a subduction zone. It is found in volcanic arcs , and in cordilleran mountain building , such as in the Andes Mountains . However, while its extrusive volcanic equivalent, andesite, is common in these settings, diorite is a minor component of the plutonic rocks, which are mostly ...