Formation conditions of granitoids of Middle-Dnieper granite-greenstone area
© O.V. Usenko, 2014
The paper focuses on revealing conditions of granite formation in the Archean. It has been shown that appearance of the deepest
ultrabasic melts, producing comatiites of the konka series is temporarily close to formation of dnipropetrovsk and sura
granitoids - 3,11-2,95 Ga ago. A scheme of two-level crystallizing differentiation has been proposed. During granitoids formation
considerable role was played by metasomatizing fluids. Up to 2,8 Ga mantle melts were enriched by chlorine-containing water fluid. After 2,8 Ga
oxidation potential of deep fluid decreases, while potassium activity increases. Chemical and mineral composition of granites changes.
Key words: granite formation, crystallization differentiation, metasomatic replacement, Precambrian, fluid.