ABSTRACT
The various processes responsible for the evolution of a comagmatic suites are frequently grouped together and called the magmatic differentiation processes. Evidence that the process of fractional crystallisation has operated during the evolution of many rocks is readily uncovered in the compositions of mesostases of most porphyritic basic and intermediate volcanic rocks. Liquid immiscibility is believed to hold the key to understanding the evolution of the carbonatite–ijolite–nephelinite rock association. Normally when magma contacts the near vertical walls of a magma chamber a temperature gradient develops with heat being conducted into the country rocks. Prior to eruption, magmas usually contain volatile components that are held in solution by the confining pressure. A unique process that operates during the movement of a magma is called flowage differentiation. The process of assimilation occurs when a magma incorporates and digests foreign material. Many attempts have been made to discover the chemical composition of the parental magma responsible sible for the Archean anorthosites.
