The effect of pressure and spin on the isotopic composition of ferrous iron dissolved in periclase and silicate perovskite

TL;DR

This study uses density functional calculations to show how pressure and spin states influence the isotopic composition of ferrous iron in Earth's mantle minerals, impacting planetary iron isotope distribution.

Contribution

It provides the first detailed computational analysis of how pressure and spin transitions affect iron isotope ratios in mantle minerals.

Findings

Pressure increases 57Fe/54Fe ratios in mantle phases.

Spin transition significantly influences isotope fractionation.

Pressure-induced fractionation impacts planetary iron isotope composition.

Abstract

We perform density functional calculations of the equilibrium 57Fe/54Fe ratios for ferrous iron dissolved in periclase and MgSiO3 perovskite at the pressures and temperatures of the Earth's mantle. Pressure increases the partitioning of 57Fe into both phases by a factor of three from the Earth's surface to the core-mantle boundary. In ferropericlase, a large contribution to this increase comes from the electronic transition from high-spin to low-spin iron. Our calculations demonstrate that pressure-induced fractionation can play a major role in determining planetary iron-isotope composition.