Igneous rock 的crystalization 係點 ga?

Fractional crystallization(Crystalization) of igneous rocks is one of the process of Igneous differentiation.

Fractional crystallization is one of the most important geochemical and physical processes operating within the Earth's crust and mantle.

Fractional crystallization is the removal and segregation from a melt of mineral precipitates, which changes the composition of the melt.

Fractional crystallization in silicate melts (magmas) is a very complex process compared to chemical systems in the laboratory because it is affected by a wide variety of phenomena. Prime amongst these is the composition, temperature and pressure of a magma during its cooling.

The composition of a magma is the primary control on which mineral is crystallized as the melt cools down past the liquidus. For instance in mafic and ultramafic melts, the MgO and SiO2 contents determine whether forsterite olivine is precipitated or whether enstatite pyroxene is precipitated.

Two magmas of similar composition and temperature at different pressure may crystallize different minerals. An example is high-pressure fractional crystallizaion of granites to produce single-feldspar granite, and low-pressure conditions which produce two-feldspar granites.

The partial pressure of vapor phases in silicate melts is also of prime importance, especially in near-solidus crystallization of granites.