Bowen's Reaction Series refers to the order in which various minerals crystallize from magmatic melt in order of decreasing temperature. In consists of two series, contineuous and discontinuous.
History
According to experiments by N.L. Bowen in the early 20th century, it is possible to derive mafic and felsic magma from a common parental source through differentiation. Bowen showed that minerals with the highest melting temperature crystallize first, followed successively by minerals of lower melting temperature.
Discontinuous branch
One mineral changes to another at discrete T during cooling and solidification of the magma. All the minerals involved are ferromagnesian. The crystallization proceeds as follows: olivine >' pyroxene > amphibole > biotite 'Any magma remaining after biotite has finished crystallizing is devoid of Fe and Mg
Continuous branch
Plagioclase feldspar is the only mineral in the continuous branch As the magma cools, the Ca-plagiocalse, which has the highest melting T, crystallizes first. As the Ca is spent, it is replaced by Na, such that subsequent plagioclase crystals become progressively enriched with Na:
anorthite > bytownite > labradorite > andesine > oligoclase > albite
Magma left after all the plagiocalse has crystallized is richer in Si and contains K and Al. they combine to form K-feldspar. Muscovite may also form if water pressure is high. Excess silica crystallizes as quartz.
The differentiating magma may be interrupted at any point along its differentiation path and solidify or be erupted at the surface, resulting in magmas of different compositions.
The continuous and discontinuous series merge as temperatures and pressures reduce to crystallise the following members: