Other diagrams (such as the one shown on the right), depict the relationships between a number of compounds having different compositions. Still others show how compositions of phases change under different conditions. Pseudosections are a type of phase diagram that shows the fields of stability of different equilibrium mineral assemblages for a single bulk-rock composition. Standard phase diagrams may include many reactions but, depending on its composition, a particular rock may only experience a few (or none) of them. Pseudosections only include those reactions that affect a particular composition. Fields on a pseudosection are labeled (specifying the equilibrium mineral assemblage) with the reaction lines unlabeled (although the specific reaction can be deduced). This is a diverse collection of phase diagrams, intended to be used by instructors when teaching petrology or mineralogy classes.Ĭlick image to enlarge.
