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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]
Decompression melting in upwelling asthenosphere likely begins at a depth as great as 100 to 150 kilometers (60 to 90 mi), where the small amounts of volatiles in the mantle rock (about 100 ppm of water and 60 ppm of carbon dioxide) assist in melting not more than about 0.1% of the rock. At a depth of about 70 kilometers (40 mi), dry melting ...
The lithosphere–asthenosphere boundary (referred to as the LAB by geophysicists) represents a mechanical difference between layers in Earth's inner structure. Earth's inner structure can be described both chemically (crust, mantle, and core) and mechanically. The lithosphere–asthenosphere boundary lies between Earth's cooler, rigid ...
The seismic velocities very near the surface (≲ 220±30 km) are markedly lower than at greater depths, demarking the LVZ. The low-velocity zone (LVZ) occurs close to the boundary between the lithosphere and the asthenosphere in the upper mantle. It is characterized by unusually low seismic shear wave velocity compared to the surrounding depth ...
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 ...
The role of partial melting is demanded by experimental and field evidence. Rocks begin to partially melt when they reach a combination of sufficiently high temperatures (> 650 °C) and pressures (>34MPa). Some rocks have compositions that produce more melt than others at a given temperature, a rock property called fertility.
The rock cycle explains how the three rock types are related to each other, and how processes change from one type to another over time. This cyclical aspect makes rock change a geologic cycle and, on planets containing life, a biogeochemical cycle. Structures of Igneous Rock. Legend: A = magma chamber (batholith); B = dyke /dike; C = laccolith ...