Fractional Crystallization (Geology) (Paperback)

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; except in special cases, removal of the crystals changes the composition of the magma. Fractional crystallization in silicate melts is complex compared to crystallization in chemical systems at constant pressure and composition, because changes in pressure and composition can have dramatic effects on magma evolution. Addition and loss of water, carbon dioxide, hydrogen, and oxygen are among the compositional changes that must be considered. For example, the partial pressure of water in silicate melts can be of prime importance, as in near-solidus crystallization of magmas of granite composition. The crystallization sequence of oxide minerals such as magnetite and ulvospinel is sensitive to the oxygen fugacity of melts, and separation of the oxide phases can be an important control of silica concentration in the evolving magma, and may be important in andesite genesis.