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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 known as a magma series.
Magma that is extruded as lava is extremely dry, but magma at depth and under great pressure can contain a dissolved water content in excess of 10%. Water is somewhat less soluble in low-silica magma than high-silica magma, so that at 1,100 °C and 0.5 GPa, a basaltic magma can dissolve 8% H 2 O while a granite pegmatite magma can dissolve 11% ...
The magma, which is brought to the surface through fissures or volcanic eruptions, rapidly solidifies. Hence such rocks are fine-grained or even glassy. Basalt is the most common extrusive igneous rock [9] and forms lava flows, lava sheets and lava plateaus. Some kinds of basalt solidify to form long polygonal columns.
In some compositions, at high pressures without water crystallization of enstatite is favored, but in the presence of water at high pressures, olivine is favored. [12] Granitic magmas provide additional examples of how melts of generally similar composition and temperature, but at different pressure, may crystallize different minerals.
Anorthosite (/ əˈnɔːrθəsaɪt /) is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present. Anorthosites are of enormous geologic interest, because it is ...
Plutonism. Plutonism is the geologic theory that the igneous rocks forming the Earth originated from intrusive magmatic activity, with a continuing gradual process of weathering and erosion wearing away rocks, which were then deposited on the sea bed, re-formed into layers of sedimentary rock by heat and pressure, and raised again.
The sanidinite facies is a rare facies of extremely high temperatures and low pressure. It can only be reached under certain contact-metamorphic circumstances. Due to the high temperature the rock experiences partial melting and glass is formed. This facies is named for the mineral sanidine. It is characterized by the following mineral assemblages:
The lower pressure, high temperature, and now volatile rich material in this wedge melts and the resulting buoyant magma rises through the overlying rock to produce island arc or continental margin volcanism. This volcanism includes more silicic lavas the further from the edge of the island arc or continental margin, indicating a deeper source ...