Igneous and metamorphic petrology in the last decades of the twentieth century exploded into a broad, multifaceted, increasingly quantitative science. Advances in physical and field petrology and geochemistry have forever changed our thinking about the origin and evolution of magmas, their dynamic behavior, and the way in which they are intruded and explosively extruded. Developments in geochronology, quantitative evaluation of the role of heat and fluid transfer in crustal rocks, and new field discoveries have impacted our understanding of the evolution of metamorphic systems and their dynamic interaction with tectonic processes. Geophysics and mineral physics have provided new insights into the nature of the convecting mantle and its role as a giant heat engine driving magmatic and metamorphic processes. New tools of all kinds allow new ways of gathering petrologic data, while phenomenal developments in computers and computer software permit data to be stored, processed, and modeled in ways unimaginable as recently as a couple of decades ago.

My main objective in writing this book has been to review the processes involved in present-day magma generation and their relationship to global tectonic processes. Clearly, these are fundamental to our understanding of the petrogenesis of ancient volcanic and plutonic sequences, the original tectonic setting of which may have been obscured by subsequent deformation and metamorphism.

The purpose of this book is to stimulate the reader ’ s interest in magmatic rocks and processes, to develop key skills of describing,
classifying and naming such rocks, and to show how much we can learn about igneous processes from careful, informed interpretation of rock textures, mineralogy and geochemistry. The book is aimed primarily at the intermediate - level student of geology who already has a basic knowledge of igneous rocks, but anyone starting from scratch should fi nd that the opening chapter and relevant boxes –together with the Glossary –provide the minimum introduction they require. The emphasis throughout the book will be on practical investigation, mainly by means of the polarizing microscope; basic mineral - identifi cation data have therefore been included to provide –between one set of covers –all that the student needs during a typical igneous practical class. <...>