|Rearrangement of the electrons in iron upon pressure-induced spin transition in carbonates.|
Upper mantle carbonates are magnesium-rich and iron-poor. Under lower mantle conditions, it is thought that the arrangement of electrons in carbonate minerals changes under the pressure stress in such a way that iron may be significantly redistributed. A research team has now focused on the high-pressure chemistry of a carbonate mineral called siderite, FeCO3, commonly found in hydrothermal vents. Their findings help resolve questions about the presence of iron-containing lower mantle carbonates.