Principles of igneous and metamorphic petrology / Принципы магматической и метаморфической петрологии

This chapter introduces rocks and petrology, the science that attempts to explain the origin and distribution of rocks. Rocks are the solid material constituting the Earth, and it is essential to know what composition the planet has. We begin with a brief review of the planetary formation process and how it determined the Earth’s composition and major divisions into core and mantle. Early impacts, the largest of which generated the Moon, caused extensive melting, and since then the planet has been cooling, with convection of the mantle being a major consequence. During at least the last 3.0 Ga, a rigid lithosphere has existed, fragments of which have been moved around by the convecting mantle in what we refer to as plate tectonics. Most rocks have been generated in response to this movement. We therefore review how mantle convection and plate tectonics bring about conditions in which new rocks are formed. One of the main ways in which the planet has cooled is by the generation in the upper mantle of partial melts, which on rising toward the surface transfer heat and produce igneous rocks. This heat also brings about reactions that generate metamorphic rocks, which commonly release volatiles that rise toward the surface, transferring heat as they do so. This chapter presents an overview of these processes. In this introductory survey, references to later sections in the book, where a more detailed discussion will be found, are given. <...>