Location pattern and genetic classification of granite pegmatites of the Ukrainian Shield

Abstract

The pegmatites of the Ukrainian Shield, their formation and occurrence are con- sidered. It is shown that the Ukrainian Shield is a pegmatite province encompassing seven regions: Middle Prydniprovia, Western Pryazovia, Eastern Pryazovia, Ingulski, Rosynsko- Tikytski, Dnistersko-Buzki and Volyn, respectively encompassing megastructures of the same names and including pegmatite fields of different mineralogical composition and geochemical specialization. The Volynski, Ingulski, Middle Prydniprovia, Western Pryazovia regions have rare-earth and rare-metal specialization presented by pegmatites of different origin and petrological and mineral composition and occurring in different structural and tectonic conditions, having different formation age, which allows a full classification scheme of the pegmatites of Ukrainian Shield to be given. These structures can be considered as having formed as a result of abyssal magmatic plumes. The geological-structural position of these megastructures with obvious signs of influence of certain abyssal processes on their formation supports this assumption. We present the main geological structural and genetic factors of formation of pegmatite-bearing megastructures of the Ukrainian crystalline core-area, these factors forming the basis of a classification scheme of pegmatites of Pre-Cambrian shields. We have systematized the pegmatites of the Ukrai- nian Shield , and designed their classification scheme . We have distinguished the following groups of pegmatites by the development of pegmatite-generating zones: - three genetic groups of pegmatites: ultrametamorphogenic, magmatogenic and metamorphogenic-meta- somatic; - six genetic subgroups of pegmatites: migmatic; autochthonous granite massifs; metamorphogenic and metasomatic displaced and formed pegmatites; multiphase intrusive granite massifs; multiphase intrusive alkaline massifs; multiphase granite batholiths. By the nature of pegmatite-bearing structures, the following structural groups have been singled out: granite-gneiss regional structures and domes; dome- synclinore and dome-trough plume-structures (subgroups: interdome synclinore and trough structures, in particular greenstone structures; intrusive domes and batholiths); specific tectonic zones of stress tensions.