Evolution of parental melts of alkali ultrabasic intrusive massives of Maimecha-Kotui Province (Polar Siberia)

Computational modeling based on data on the compositions of melt inclusions in chrome-spinelids using the COMAGMAT [12] and PETROLOG [11] programs indicates the similarity of the parent melt of meimechites [4] with the picritic magma of the Gulinsky massif. Experimental data on the inclusions confirm this conclusion, showing the reliability of the actually calculated trends in the fractionation of ultrabasic melts. In general, the calculations showed that the crystallization of olivine from the high-magnesium pyrite melt occurred in the temperature range of 1510-1260 ° C, mainly at a pressure of 6-7 kbar. At the same time, the melt evolves and approaches its composition to olivine basalt, from which, starting from 1200 ° C, clinopyroxene mainly crystallizes with enrichment of the residual melt with alkalis, rare and rare-earth elements. The similarity of the compositions of the parental melts for meimechites and Gulinsky pluton rocks and the proximity of P - T parameters of their evolution indicates a possible genetic relationship of these magmatic formations.