Formation of Iron Hydride and Iron Carbide from Hydrocarbon Systems at Ultra-High Thermobaric Conditions

Abstract

Abstract—The chemical interaction of hydrocarbon systems and iron-bearing minerals was investigated under extreme upper mantle pT conditions. As a result, the formation of iron carbide and iron hydride was detected. The experiments were carried out in diamond anvil cells with laser heating. Natural crude oil from the Korchaginskoe deposit and a synthetic mixture of paraffin hydrocarbons were used as hydrocarbon systems and pyroxene-like glass and ferropericlase (⁵⁷Fe enriched) were used as iron-bearing minerals. The experiments were carried out in the pressure range of 26–95 kbar and the temperature range of 1000–1500°C (± 100°C). The formation of iron hydride was detected at pressure of 26–69 kbar (corresponds to a depth of 100–200 km), and a mixture of iron carbide and iron hydride is formed at pressure of 75–95 kbar (corresponds to a depth of 210–290 km). The formation of iron hydrides and carbides through the interaction of hydrocarbon systems with iron-bearing minerals may indicate the possible existence of these compounds in the upper mantle.