This book examines the pre-orogenic geological development of the Sayan-Altai geosynclinal region, primarily its tectonic evolution, as well as certain general problems concerning magmatism, metamorphism, and the structural characteristics of the Earth's crust in this area. In recent years, these issues have been extensively discussed in numerous monographs and articles that summarize the large body of factual material obtained through geological mapping and specialized investigations carried out in the Sayan-Altai region over the past ten to fifteen years. However, most of these studies have rarely attempted to provide an integrated analysis of the geological development of the Sayan-Altai region as a whole. Consequently, although the geology of the region has been studied quite thoroughly, there has still been no comprehensive synthesis based on modern integrated research that examines all known geological evidence from the perspective of a specific conceptual framework. Although geological research in the Sayan-Altai region is generally based on the same set of facts known to all geologists working there, different investigators often interpret these materials in entirely different ways. This situation arises, first, from the lack of sufficiently rigorous data for resolving certain geological problems of the Sayan-Altai region; second, from the possibility of multiple interpretations of the available data; and third, from the specialized nature of many studies. In addition, researchers often differ in their general theoretical viewpoints. All of this creates certain difficulties for anyone attempting to synthesize a large body of material that has been subject to highly diverse interpretations. Naturally, the most fundamental way to overcome these difficulties would be to undertake extensive additional investigations of the principal geological problems of the Sayan-Altai region and, on the basis of more complete evidence, to develop a series of broader theoretical issues in geology. However, such an undertaking would not constitute a summary of work already completed but rather the beginning of a new stage of research, which in itself cannot be the purpose of the present work. Therefore, the author considers it most appropriate to limit the scope of this study to an examination of the existing monographic literature from the standpoint of a particular geological concept that most closely corresponds to the views he has developed through many years of research on the geology of the Sayan-Altai region. Like many of the fundamental theoretical problems of geology as a whole, all of these concepts are well known to geologists. They are based on certain hypothetical propositions which, at present, cannot yet be fully substantiated.