Petrogenesis of meymechites of Sikhote Alin inferred from melt inclusions

Abstract

The analysis of the composition of minerals and their melt inclusions yielded new information on the physicochemical conditions that determined the formation of Sinkhole Alin meymechites. The data on the compositions of the minerals in ultramafic subvolcanic rocks from two localities (Barakhta and Katen rivers) indicate the similarity of these meymechites with standard rocks in the Maimecha-Kotyi province and their formation in untraplate environments. The experiments with melt inclusions in olivine and calculations using the data on the compositions of glasses in the inclusions revealed insignificant differences in the thermal regimes of the magmatic systems during the formation of meymechites from the Barakhta (1235–1280°C) and Katen (1230–1300°C) river localities. The investigations of inclusions in olivine show that the meymechites of Sikhote Alin crystallized from basaltic melts (corresponding in their chemical composition to olivine basalts and picrobasalts) due to cumulation of olivine. The data on the distribution of the titanium, trace, and rare earth elements in the melt inclusions imply a significant contribution of plume systems to the formation of the meymechite complexes of Sikhote Alin. The direct analysis of the compositions of the volatile components in the glasses from the heated melt inclusions in olivine using an ion microprobe revealed significant differences in the concentrations of water in the magmatic systems that formed the meymechites of the Barakhta (0.82–0.90 wt % to 2.45 wt %) and Katen (0.22–0.30 wt %) river basins.