<Dl> <Dd> Main article: Igneous differentiation </Dd> </Dl> <Dd> Main article: Igneous differentiation </Dd> <P> Most magmas only entirely melt for small parts of their histories . More typically, they are mixes of melt and crystals, and sometimes also of gas bubbles . Melt, crystals, and bubbles usually have different densities, and so they can separate as magmas evolve . </P> <P> As magma cools, minerals typically crystallize from the melt at different temperatures (fractional crystallization). As minerals crystallize, the composition of the residual melt typically changes . If crystals separate from the melt, then the residual melt will differ in composition from the parent magma . For instance, a magma of gabbroic composition can produce a residual melt of granitic composition if early formed crystals are separated from the magma . Gabbro may have a liquidus temperature near 1,200 ° C, and the derivative granite - composition melt may have a liquidus temperature as low as about 700 ° C. Incompatible elements are concentrated in the last residues of magma during fractional crystallization and in the first melts produced during partial melting: either process can form the magma that crystallizes to pegmatite, a rock type commonly enriched in incompatible elements . Bowen's reaction series is important for understanding the idealised sequence of fractional crystallisation of a magma . </P>

Different types of intrusive and extrusive igneous rocks