Water, iron, redox environment: effects on the wadsleyite–ringwoodite phase transition

The transition zone of the Earth’s upper mantle is characterized by three discontinuities in seismic wave velocity profiles. One of these at about a depth of 520 km is assigned to the transformation of wadsleyite (β-) to ringwoodite [γ-(Mg, Fe) 2 SiO 4 ] (e.g., Shearer in J Geophys Res 101:3053–3066, 1996 ). The exact location, width, and other properties of that discontinuity are affected by a multitude of parameters. The present study specifically focuses on the effect of water, iron content, and redox environment on the depth of the phase transition. We performed high-pressure experiments in a multi-anvil apparatus at 1200 °C with variation in Mg–Fe compositions (0.10