ONGONITE DIKES OF EASTERN KAZAKHSTAN AND THE SPECIFICITY OF THEIR ORE CONTENT

Goal of the research is to study regularities, age, material composition and ore content of ongonite-like dike belts of East Kazakhstan. Methods are field works carried out within Kalba-Narym shear zone where dike belts are developed. Geological and structural position of dikes and their age ratio to granitoids of Kalba-Narym pluton and ore formations have been determined. The samples were selected from varieties of ongonite dikes. Microprobe analyses have been carried out on a scanning election microscope JSM 6390 with an energy-dispersive add-on device, besides, mass-spectrometer researches have been conducted on ICP-MS. The purpose of these is to identify mineralogical and geochemical specialization of dike rocks. Findings. The following has been found due to the conducted researches and comparison analysis with other regions: Two groups of heterochronous dike belts were formed during Hercynian Period in geological structures of East Kazakhstan comprised in general system of Central Asian belt. The dike belts belong to gabbro- diorite – granodiorite – plagiogranite series, and the groups are of pre-batholite (C2-3–C3) and post-batholite (P2) types. Late postbatholite dikes of quartz porphyrites and quartz albitophyres of Mirolyubovsky complex (P2) refer to ongonites. Probably, they are derivatives of deep residual magma chambers. In the course of the work, ongonites geochemical differentiation into rare metals(Ti, Nb, Li, Sn, W and other) and rare alkalies has been established. The researches have shown that ongonite-like dikes are of post-mineral nature that is proved by their position in relation to ore bodies and by other factors. Besides, no rare metal ore of practical significance has been found within these dikes. Scientific novelty and practical application. It can be assumed that greater development of gabbro- diorite – granodiorite – plagiogranite dikes within the known and supposed ore fields, as well as specialization of rocks that dikes are composed of, enable to consider them as prospecting indicators of concealed rare metal objects. To study dike formations of this kind is very important for reconstruction of geodynamic environments, for development of correlation patterns of granitoid magmatism and for studying ore formation processes. By all means, all this can be used in geologic mapping practice, especially on the closed territories.