Mineralogy of olivine rocks and conditions of their formation (Zhokhov island, New Siberian islands, Russia)

This paper is dedicated to results of microscopic study of minerals from xenoliths of mantle spinel lherzolites in Cenozoic basaltoids of Zhokhov Island (New Siberian Islands, Russia) using microanalysis and Raman spectroscopy, as well as the assessment of formation conditions (T, P, fO2) of the olivine-spinel mineral assemblage. Olivine is one of the major minerals of spinel lherzolites of the Zhokhov Island. It contains numerous syngenetic and later mineral and fuid inclusions. The solid-phase inclusions include enstatite, diopside, spinel, apatite, sulfdes, and solid hydrocarbons identifed by Raman spectroscopy as kerogen and bitumen. Based on results of Raman spectroscopy, fuid inclusions contain CO2 and, locally, a mixture of CO2 (97.5 %) and CO (2.5 %). According to various geothermometers, the average temperature of co-existence of the olivine-spinel assemblage is 1010 K (737 °C) at a pressure of 1 GPa. Oxygen fugacity (lgfO2) for lherzolites of the Zhokhov Island ranges from –13.9 to –14.6.