Question - Describe the main mechanism through which a magma chamber could become zoned.

Describe the main mechanism through which a magma chamber could become zoned.

Answer:

There are two important processes. One is fractional crystallization, which is the crystallization of some minerals – typically ferromagnesian minerals – before others. If those minerals settle to the bottom of the magma chamber that will make the composition more felsic at the top and more mafic at the bottom. The other is partial melting of the surrounding rock, or of xenoliths that fall into the magma, both of which are likely to make the magma more felsic overall.