The origin of anorthosites is a major unsolved petrogenetic problem in igneous petrology. For most of the numerous types of anorthosite that occur on Earth (and on other planets as well), we cannot agree as to their parental magma composi- tions, the sources and methods of generation of these mag- mas, the mechanism of plagioclase accumulation, or their tectonic setting. This book represents the only comprehensi- ve review of what is known and unknown about all anorthosite types, both terrestrial and extraterrestrial. Descriptive, interpretative, and speculative information is given for all...