Igneous differentiation

Igneous differentiation is the set of processes that change magma’s composition as minerals crystallize, separate, or interact with surrounding rocks.

Fractional crystallization: A process in which crystals are removed from a melt as they form, changing the melt’s composition. Removing early crystals leaves the remaining magma chemically distinct.
Magma: Molten or partly molten rock beneath Earth's surface, containing liquid, crystals, and dissolved gases. Differentiation describes changes to magma as it evolves.
Layered intrusion: A large igneous body with distinct layers formed by repeated crystallization and accumulation of minerals. Layering preserves physical evidence of crystal separation within magma.
Trace element: A chemical element present in a rock or mineral at low concentration, often measured in parts per million. Trace-element patterns can test whether crystal removal produced observed magma compositions.
Bowen's reaction series: A model describing the order in which silicate minerals crystallize from cooling magma. Its crystallization sequence predicts which elements early minerals remove from melt.
Silicate minerals: Minerals built chiefly from silicon-oxygen tetrahedra, the dominant mineral group in Earth's crust and mantle. Their differing compositions and crystallization temperatures drive many differentiation trends.
Komatiite: An ultramafic volcanic rock, exceptionally rich in magnesium and associated mainly with ancient Earth. Its olivine-rich compositions reveal high-temperature melting and crystal fractionation.
Rare-earth element: One of the lanthanides, plus yttrium and scandium in many geochemical classifications. Rare-earth patterns help identify minerals controlling melt evolution.
Crystal settling: The downward movement of dense crystals through magma under gravity. Settling can physically separate crystals from the liquid that formed them.
Mafic minerals: Silicate minerals rich in magnesium and iron, such as olivine and pyroxene. They commonly crystallize early and draw iron and magnesium from magma.

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TonaliteRelated: Differentiation can produce the silica-rich compositions that crystallize as tonalite.