Vol 43 Iss. 2

Brief description of mariupolites. An alkaline rock specific in composition and structure, named mariupolite by I. A. Morozevich, is the youngest relative to the granites, syenites, and foyaites that compose the Oktyabrsky (Mariupol or Azov) alkaline massif in Ukraine.

During the study of Iceland spar crystals from the Nizhne-Tunguska deposits, more than 15,000 pieces cleaved along cleavage were examined, of which some were completely colorless, while the majority were colored yellow of varying intensity. By the intensity of coloration, all crystals were divided into fifteen classes: zero, I–XIV.

The natural thermal state of rocks is disturbed in the vicinity of a borehole during drilling. The degree of disturbance of this state depends on many causes.

Geophysical methods for prospecting bauxite deposits began to be used in the Soviet Union and abroad more than 20 years ago. Many methodological issues remained insufficiently studied for a long time. This led to large unproductive costs and delayed the development of the application of geophysical methods and the discovery of new bauxite deposits.

The successful use of lithochemical methods in prospecting for ore deposits by their secondary halos and dispersion trains, and the solution of the question of the advisability of conducting one or another type of survey (lithochemical or hydrochemical) or their combined use in prospecting works of a certain scale—all this requires a deep analysis of the paths and conditions of migration of various elements in eluvial-deluvial deposits.

A large number of deposits of ores of various metals and many non-metallic minerals are associated with carbonate rocks. According to I. I. Knyazev, more than half of the world's production of zinc and lead comes from deposits occurring in limestones and dolomites. Polymetallic deposits of the replacement type in limestones and skarn-type deposits are widespread in Transbaikalia, Central Asia, and other ore regions. According to V. S. Kormilitsyn, about 90% of polymetallic deposits in one of the regions of Eastern Transbaikalia, including all the larger objects, are confined to dolomites; about 8% of deposits are in limestones. Many deposits of iron, manganese, copper, silver, gold, mercury, and other metals are associated with carbonate rocks. In many ore regions of the Union, lead-zinc and other hydrothermal mineralization, as noted by F. I. Wolfson, is localized within structural levels enriched in carbonate sequences, while such mineralization is completely absent in deeper structural levels composed of various shales, quartzites, effusive rocks, and other rocks enriched in aluminosilicate components. Epigenetic mineralization forming among carbonate rocks is more often observed in dolomite horizons than in limestones. In this connection, the identification of dolomites acquires significant importance in geological mapping and prospecting.

Check chemical analyses are absolutely mandatory during exploration works. In the case of significant discrepancies between the results of the primary and check analyses, the primary ones must be corrected or re-analyzed. The role of check analyses is very important in cases where the content approaches the limit of sensitivity of the analysis (for rare elements and trace elements). Discrepancies between primary and check analyses arise from random and systematic errors. When calculating average contents over a large number of samples, the influence of random errors is small, since they have different signs and cancel each other out. The influence of systematic errors, which are revealed by external control, is much stronger.

During geological mapping, prospecting, and especially exploration of mineral deposits, a very important role is assigned to geophysical and geological exploration works. As a result of borehole drilling and mine workings, the following tasks are solved: a) the position of ore bodies in the section, their boundaries, and thickness are established, which serves as the basis for calculating coordinates at the points where ore bodies are intersected by geological exploration workings; b) natural types, and often commercial grades of ores, are distinguished, thereby revealing the structure of ore deposits; c) rock material is sampled, which helps in studying the mineral composition of ores and their assaying. The generalization of data from a number of geological exploration workings will make it possible to establish the dimensions, shape, and conditions of occurrence of ore bodies, and to clarify the mining and technical conditions for developing the deposit.

The comprehensive use of deposits necessitates the systematization of useful components, taking into account their economic significance, concentration, and distribution in ores, and, in connection with this, the systematization of the types of samples taken according to their purpose.

Phenomena of hybridization were studied in the pluton "Sidorovsky Ural" located in the northeastern part of the Minusinsk basin. This pluton is the eastern end of a chain of essentially nordmarkite bodies, extending along the northern side of the Minusinsk basin at its junction with the Eastern Sayan. Spatially and genetically, the nordmarkite intrusions are closely associated with the Lower Devonian basic subalkaline and acid effusive rocks, with which they form a single magmatic association of the marginal part of the Minusinsk depression. In terms of depth, the nordmarkite intrusions belong to shallow-depth intrusions, geochemically characterized by a predominance of sodium over potassium and by rare-earth mineralization.

An increasing amount of factual data testifies to the significant role of postmagmatic phenomena in the formation of alkaline rocks. It is becoming clear that the wide variations in the structure and even composition of rocks, which are so characteristic of alkaline massifs, are to a large extent associated with postmagmatic processes. The formation of ore and rare-metal minerals in alkaline massifs is also associated with these processes. However, the question of the source of postmagmatic solutions has not yet been resolved. Most researchers consider the source of these solutions to be alkaline magma rich in volatile components, which fills the corresponding cavity, i.e., the postmagmatic phenomena described in alkaline massifs belong to the phenomena of autometamorphism (autopneumatolysis, autometasomatism). The processes of fenitization of the rocks hosting the massifs are attributed to the metasomatic processes of the magmatic stage.