Igneous Differentiation

Igneous differentiation, also called magmatic differentiation, is the umbrella term for the processes by which a magma undergoes bulk chemical change while it is forming by partial melting, cooling, emplacement or eruption. The sequence of usually increasingly silicic magmas that results is known as a magma series. The primary cause of the change is cooling, which makes minerals crystallize out of the melt, and the composition can also change through contamination, by assimilation of wall rock, mixing of two or more magmas, or replenishment of the chamber with fresh hot magma. The full set of mechanisms is sometimes called the FARM process, for fractional crystallization, assimilation, replenishment and magma mixing. Geologists use the ideas of primary, parental and cumulate melts to work back from observed rocks to the magma they came from.