Basalts and Phase Diagrams : an Introduction to the Quantitative Use of Phase Diagrams in Igneous Petrology

The science of igneous petrology is founded on astute observation of rocks, guided by the rigorous principles of physical chemistry. It is, perhaps, the wedding of fallible observation with rigorous theory that makes this such a delicious science. In view of this, it is appropriate to study rocks and phase diagrams hand in hand. Good books on petrography abound, but there are few introductory books on phase diagrams, and none that illustrate in detail the quantitative analysis of fractional and equilibrium crystalliza­ tion and melting, the four limiting processes capable of rigorous discussion. This book is an attempt to remedy the deficiency. Basalts underlie some 70 percent of the earth' s surface and represent the most abundant magma type on both the earth and the moon. It is therefore fitting to address their origin in some detail. As it happens, most of the interesting principles of phase equilibrium diagrams as applied to igneous rocks can be illustrated with basalts. I have therefore tied the exposition of phase diagrams to the larger story, still unfolding, of the origin and fate of the basaltic magma. In so doing, one neglects many interesting rocks, but their origins can be studied using the principles developed here. Content: Front Matter....Pages i-xvi Introduction....Pages 1-6 Mineralogy and Chemistry of Basalts....Pages 7-19 Crystals and Melts....Pages 21-29 The Phase Rule as a Tool....Pages 31-36 Diopside and Anorthite: Supposedly a Binary Eutectic System....Pages 37-60 Plagioclase: The System An-Ab....Pages 61-75 Diopside-Albite: A Complex System....Pages 77-84 Diopside-Anorthite-Albite....Pages 85-128 Forsterite-Diopside-Anorthite: A Basaltic Analog....Pages 129-149 Incongruent Melting: The System Forsterite-Silica....Pages 151-159 Forsterite-Anorthite-Silica: Incongruent Melting in a Ternary System....Pages 161-180 Forsterite-Diopside-Silica: Pyroxenes and Their Reactions....Pages 181-215 Layered Intrusions: A First Glance....Pages 217-241 Nepheline-Silica and the Rest of the Basalt Tetrahedron....Pages 243-254 Potassium: Petrogeny’s Residua System and Ternary Feldspars....Pages 255-293 Iron and Oxygen....Pages 295-323 Iron-Bearing Olivines and Pyroxenes....Pages 325-344 The Effects of High Pressure....Pages 345-379 Effects of Volatiles at High Pressure....Pages 381-404 Some Applications to Basalt Magma Genesis....Pages 405-425 Back Matter....Pages 427-493