E-catalog        

Библиогр.: с. 29

Петрографическое исследование пород юлинского интрузивного комплекса (Южная Сибирь, Хакасия) позволило выявить главные типы пород. Установленные вариации составов породообразующих минералов отражают, главным образом, их принадлежность к определенному типу пород. Составы минералов нередко укладываются в тренды, которые, очевидно, указывают на генетическое родство пород и их образование из близких по составу магматических расплавов. The object of the study – the alkaline rocks of the Yulinsk complex, located on the southeastern slope of the Kuznetsk Alatau (Southern Siberia, Khakassia). In this work presents a generalized petrographic characteristic of all rock varieties of the Yulinsk complex. Petrographic research was carried out in detail, which made it possible to identify numerous varieties of rocks, which reflect two phases of intrusion of magmatic melts. The rocks of the first phase of formation are characterized by an average, basic composition of rocks, they are represented by gabbroids and diorites. The second phase of formation is represented by rocks of the moderately alkaline series and is more diverse in petrographic composition. The most common rocks are monzonites and syenites, with the subordinate role of alkaline syenites, quartz syenites, granosyenites and granites. The rocks have the advantage of medium to fine grained structures. A porphyry structure with a fine-grained groundmass is often manifested. In some rocks, fragments of the crown structure are noted. Such structural features obviously reflect the hypabyssal conditions of the formation of the rocks of the Yulinsk complex. The main rock-forming minerals in the rocks of the Yulinsk complex are represented by clinopyroxenes, amphiboles, biotites, plagioclases and potassium feldspars. Calcareous clinopyroxenes are more often represented by salite, or form transitional varieties to augiteor fassaite, sometimes correspond to diopside, alkaline clinopyroxenes are represented by aegirine-augites. Amphiboles in the rocks of the Yulinsk complex usually belong to magnesian hornblendes, less often to actinolites. Biotites in the rocks are mainly represented by phlogopites, less often by Mg-biotites (annite, siderophyllite). Plagioclase is more often determined by the composition of the rock and varies from andesine to oligoclase. However, its composition often becomes more acidic as a result of secondary changes. Potassium feldspar is characterized by a more homogeneous composition. Variations in the compositions of rock-forming minerals mainly reflect their natural origin. Often their compositions are almost identical. Often, the compositions of rocks fit into trends that indicate their genetic kinship, which were formed from similar in composition magmatic melts. The initial magmatic melt for the rocks of the Yulinsk complex was apparently basic magma. As they moved in the earth's crust, magmatic melts probably underwent repeated magmatic and crystallization differentiation, as well as contamination by host rocks with the formation of both normal and moderately alkaline and alkaline derivatives of melts. Their crystallization, obviously, occurred mainly in hypabyssal conditions and contributed to the formation of numerous varieties, mainly moderately alkaline rocks. The compositions of minerals in rocks are often close or reflect the evolutionary direction of changes in the compositions of derivatives of melts.