ABSTRACT
Igneous processes are responsible for heat and mass exchange in the outer layers of the terrestrial-group planets. Igneous melts originating at depth bring magma to the surface to form planetary crust. Certainly, magmatism is a complex phenomenon, and therefore the interpretation of particular types of igneous activity and their significance in the context of planetary evolution requires the application of geophysical, petrological and isotope-geochemical methods. Volcanic rocks are generally poorly crystallized; differentiation does not usually occur except for rare cases of superheated Early Precambrian komatiite or picrite melts. Intrusive igneous rocks are generated under quite different conditions, especially within large intrusive chambers, accompanied by intense fractional crystallization. In terms of magmatic series, the study of intrusions, especially layered types, provides important additional information about the true extent of a series, because all the rock types occur in the single cross-section.
