ABSTRACT

In this chapter, the author presents the principal rocks that result from regional metamorphism. This requires us to define a series of sequences showing the gradual transformation of original material into rock as a result of increasing metamorphism. Metamorphism creates a wide variety of rocks. Pressure and temperature conditions and geochemical fluxes are highly variable depending on their geologic settings and all types of rocks can be metamorphosed. Research shows that one initial material can produce different minerals depending on environmental conditions. Depending on the relative values of pressure and temperature, there are three different mineralogical forms: andalusite, sillimanite and kyanite. The presence of one of these minerals in a rock is used to determine three degrees of metamorphism, called zones. The author concentrates on the most common metamorphic conditions, that is, prograde metamorphism. In addition, metamorphic conditions are determined by the assemblage of minerals present in rocks after transformation; these assemblages define different facies.