Oxygen isotopic composition of boron minerals from kurchatovite-sakhaite ores of the Solongo deposit

The Solongo boron-magnetite skarn deposit (Western Transbaikalia, Russia) features industrial reserves of rare kurchatovite-sakhaite ores. The purpose of the work is to study the oxygen isotopic composition of boron-bearing minerals from the kurchatovite-sakhaite ores of the deposit. The samples were studied using modern methods of electron microscopy, mass spectrometry. The original photographs of transparent thin sections and images of the samples in backscattered electrons show mineral associations of sakhaite and kurchatovite icluding polymineral szaibeliite-sibirskite-calcite aggregate, roweite, fedorovskite, ludwigite, forsterite, serpentine, titanite, sphalerite, magnetite, jacobsite, apatite, turneaureite. The evolution of the Solongo deposit boron minerals is described. The following indicators of the oxygen isotopic composition δ18О v-SMOW in minerals have been obtained: sakhaite – +1 ‰, roweite – +2.7 ‰, kurchatovite – +1.9 ‰, magnetite – -0.3 ‰. The comparison of isotopic data on sakhaite with the available literature data has shown that the sakhaite of Solongo boron ores has a relatively light oxygen composition. The indicators obtained are attributed to the participation of meteoric waters including melt waters of firn basins and permafrost, in the formation process of the deposit, as well as reduced index of the oxygen isotope composition δ18O of the dolomites of the Ozerninsky ore cluster, whose transformation is associated with the sakhaite formation.