Electrical conductivity of siderite and its implication for high conductivity anomaly in the slab-mantle wedge interface

Carbonate minerals as a dominant carbon host can be transported to the Earth’s deep interior via subduction of oceanic lithosphere, and their physicochemical behavior potentially has significant influence on compositional heterogeneity physical properties in mantle. In this study, we measured electrical conductivity natural siderite at 1–3 GPa 100–700°C using complex impedance analyzer large volume multi-anvil high-pressure apparatus. A sharp increase was observed ?400°C under various pressures, subsequently, keeps anomalously high values whole temperature range owing small quantity interconnected highly conductive phases (graphite magnetite) produced from low degree decarbonation siderite. The change activation enthalpy suggest that conduction mechanisms before after are polaron (electron hopping Fe 2+ –Fe 3+ ) phases, respectively. Our results indicate incipient temperatures considerably lower than decomposition boundary determined by phase equilibrium experiments, implying initial reaction Fe-bearing carbonates subducting crust occurs shallower depth. 30 vol.% is required enhance (Mg, Fe)CO 3 solid solutions. Magnetite graphite generated component carbonate make contribution anomaly slab-mantle wedge interface.