The history of the formation of the doctrine of facies, in the development of which such a significant role belongs to D. V. Nalivkin, is marked, on the one hand, by the expansion of the range of objects covered by this doctrine, and, on the other hand, by a wider and deeper consideration of their features

Plagioclase pegmatites occupy a special place among the mica-bearing objects of the Mamsko-Chuyskaya province, which is associated with the specific geological conditions of their occurrence, composition, structure and mica-bearing.

In the works that address the problems of litho- and ore genesis, the significance of the phenomena of recrystallization is assessed in a variety of ways. Moreover, the very essence of these phenomena is interpreted differently, so it is expedient to preface the discussion by considering the content of the concepts and terms we use.

Many problems of genetic mineralogy, petrology and geochemistry were developed on the example of pegmatites. A.N.Zavaritsky, D.S.Korzhinsky and N.M.Uspensky, prominent scientists - representatives of the geological school of the Geolkom - All-Russian Geological Institute - made a very significant contribution to the development of these problems, for the first time in the domestic science paying attention to the leading role in the formation of pegmatites processes of recrystallization and metasomatosis ...

The problem of evolution of pegmatite types can be considered in several aspects.Comparison of typomorphic features of rock-forming minerals of pegmatites indicates that these features vary naturally within individual pegmatite bodies, pegmatite fields and pegmatites belonging to different formations.

The multifaceted and fruitful pedagogical and scientific activity of Vadim D. Nikitin, Professor of the Department of Mineralogy, Doctor of Geological and Mineralogical Sciences, is closely connected with the Leningrad Mining Institute, where he became a major scientist, a great connoisseur of minerals, a brilliant researcher of pegmatites.

Until now, a number of important general questions concerning the conditions of formation of quartz veins and crystal nests developed within the crustalenous fields remain to some extent debatable.

The urtites in the Khibiny massif are part of a complex ijolite-urtite complex of rocks occurring among nepheline syenites in the form of a horseshoe-shaped body hollowly falling to the center of the massif. Within this body, trachytoid ijolites are the most widespread. The so-called fine-grained iiolites are very insignificantly distributed here. According to the data of geological mapping of the ijoliturtite band, urtites lie among trachytoid ijolites and are exposed on the day surface in the hanging side or central part of the horseshoe-shaped body.

Over time, more and more examples of rational interpretation of ore field structures have been accumulated, which significantly helps further prospecting and exploration works. Over the last ten years, the intensified development of this problem has also begun in application to crustaleniferous fields. Undoubted progress has already been achieved for the fields of crystal-quartz veins (works by A. E. Karyakin, V. A. Smirnova and others in the Subpolar Urals). Deciphering of the structures of the fields of crustalene pegmatites has not yet been completed and there is no unanimous judgment on the methodological basis necessary for this ...

Pegmatite fields confined to the zone of development of Hercynian granitoid intrusions on the eastern slope of the Urals have been studied, as is known, for a very long time. To a large extent, these pegmatites are among those natural objects on the example of which the classical theory of the genesis of pegmatite formations is built ...

Despite the long study, many questions of the genesis of apatite deposits of the Khibiny massif are still unclear or debatable. Referring the reader to a thorough review of the views of various researchers, given in the work of T. N. Ivanova, we will briefly dwell on the two main directions of development of these views.Most researchers consider apatite-nepheline ores as magmatic formations. Some of them believe that apatite-nepheline ores appeared simultaneously with the host rocks as a result of liquation or crystallization differentiation of alkaline magma in situ. Others believe that the apatite-nepheline ores were formed by intrusion of an independent (phosphorus-rich) magma. It is this viewpoint that has recently been favored.

Краткое описание мариуполитовСпецифическая по составу и строению щелочная порода, назван­ная И. А. Морозевичем мариуполитом, является наиболее молодой по отношению к гранитам, сиенитам и фойяитам, слагающим Октябрь­ский (Мариупольский или Приазовский) щелочной массив на Украине.

О существенной роли постмагматических явлений в формирова­нии щелочных горных пород свидетельствует все больше и больше фактических данных. Выясняется, что в значительной мере с постмаг­матическими процессами связаны те широкие вариации строения и даже состава горных пород, которые столь свойственны щелочным массивам. С этими же процессами связано образование в щелочных массивах рудных и редкометальных минералов. Однако вопрос об источнике постмагматических растворов еще не разрешен. Большинство исследо­вателей считают источником этих растворов богатую легколетучими компонентами щелочную магму, которая заполняет соответствующую полость, т. е. описываемые в щелочных массивах постмагматические явления относятся к явлениям автометаморфизма (автопневматолиза, автометасоматоза). Процессы фенитизации пород, вмещающих мас­сивы, относят к метасоматическим процессам магматической стадии.

Touching upon the issue of zircon crystals formation in alkaline pegmatites, the author relies mainly on the results of processing the material collected during the study of mariupolites - alkaline rocks developed in the Azov part of Ukraine. However, review of the literature shows that, apparently, the nature of zircon occurring in other alkaline complexes is quite identical. The solution of this problem is closely related to deciphering the peculiarities of the formation of the host zircon mariupolites, therefore, the main features of the genesis of mariupolites are discussed below in the form in which they were reported at the meetings of the Fedorov session.

Recently, a discussion has developed regarding the genesis of pegmatites. The beginning of this discussion was laid by D. S. Korzhinsky in 1937. In 1944, A. N. Zavaritsky demonstrated the inconsistency of the physicochemical substantiation of the pegmatite process proposed by Vogt and Niggli and accepted by A. E. Fersman. Later, in 1947, he put forward a new theory of the genesis of pegmatites, contradicting the idea that pegmatites are a product of direct crystallization of residual melt (A. E. Fersman's theory). According to A. N. Zavaritsky, the main structural features of pegmatites are created as a result of recrystallization of certain igneous rocks. Next, V. D. Nikitin, who studied ceramic and mica pegmatites (1946-1951), based on a detailed analysis of the relationships between individual minerals and structural components of pegmatites, developed ideas about the genesis of pegmatites of this specific type, which are basically consistent with the theory of A. N. Zavaritsky. However, much effort is still needed to more fully resolve issues related to establishing all the features of the transformations that both the deposits as a whole and the individual minerals that make them up undergo during the complex and lengthy process of pegmatite formation. This article highlights the main features of the evolution of feldspars in ceramic pegmatites of Southern Karelia.