Evolution of magmatism of the Periazovian massif of the Ukrainian Shield and the Donets basin Part II
© Usenko O.V.
The results of studying geological structure of Periazovian massif (PM) of the Ukrainian Shield, and the Donbas (DB), experimental studies and theoretical works on parameters of the processes within the mantle have been generalized in the paper. The history of development of the region has been presented and the main features of composition of magmatic and metasomatic rocks of each stage have been briefly described. It has been revealed that magmatic rocks produced 3,67-2,8 Ga ago correspond to the result of melting the mantle lherzolite. The rocks of Proterozoic activization cycle (2,1-1,79 Ga) were formed under conditions of high sodium alkalinity, low oxygen fugasity, presence within the mantle of chemically active elements and compounds, which extract rare and disseminated elements from the primitive mantle. The melts of the Hercynian cycle (0,4-0,2 Ga) inherit geochemical specialization of residual melts of the Proterozoic cycle. The main difference is the drop of concentration of active elements, decrease of aggressive character of melts and metasomatizing (hydrothermal) solutions. Lamprophyres of the Miuss complex (0,16 Ga) were differentiated in equilibrium with the lherzolite mantle. Evolution of the melts, which appear on the surface reflects the evolution of the mantle within the region. The fact of correlation of the mantle and crust development at each stage supports the idea that the processes on the surface reflect the evolution of the deep horizons of the Earth.