MELANOCRATIC ROCKS OF THE KALYUMNY AREA ( the Synnyr alkaline basin )

Melanocratic rocks form a dense network of subparallel closed bodies in northeastern Kalyumny area and lie in accordance with the general dip of synnyrite belt structure. While being studied shonkinitoid bodies have been grouped into three types. The first type is characteristic of small bodies and is made up of homogeneous fine-grained shonkenites or melanopulaskites. The second and third types are larger bodies with distinct layers: 2nd type (from center to periphery) – fine- and medium-grained shonkinites – porphyric shonkinites – melanopulaskites – pulaskites; in the 3rd type, mica pyroxenites make up the central part. The bulk composition in a number of rocks of mica pyroxenite – shonkinites – pulaskite naturally vary toward their enrichment by Si, Al, K and depletion in femic components and phosphorus forming a common evolution trend with country synnyrites. Chemical composition of rock-forming minerals also vary regularly in this rock goup; iron, AI2O3 and TiO contents in pyroxenes and iron content in biotites increase. It is noted that the Kalyumny area shonkinitoid bodies are comparable with melanocratic bands (rhythms) of the upper leucocratic series of other synnyrite-bearing massifs by some features. Hence, it may be concluded that the Kalyumny area melanocratic rocks are syngenetic components of the upper leucocratic series of the Synnyr alkaline massif.