As the composition of the magma depends on the ricks form which it was formed along with the condition of the melting, has a high level of iron, magnesium, and calcium, and is likely to be determined by the oxygen and the silicon.
And virtually all the igneous rocks are derived for the magmas that are caused by the partial melting of the original rocks, either in the upper mantle o the crust.
The main mechanism, that meets the cracks in the zone is called the decomposition melting or the flux melting as the ricks are being moved to the surface. Thus magma continues to cool and the crystals start to form.
