Temperature Dependence of H2O Solubility in Al-Free Stishovite

Abstract

The role of stishovite in transporting water in subducting slabs has been a subject of debate for several decades. Here we investigated stishovite's water solubility and its potential role in water transportation as a function of temperature from 1300 to 2100°C at 22 GPa. Under water-saturated conditions, high-quality, Al-free stishovite single crystals were synthesized with multi-anvil press, and their water contents were measured using infrared spectroscopy. The H2O solubility in stishovite increases from 128(20) to 521(47) wt. ppm with increasing temperature from 1300 to 1700°C and decreased to 145(26) wt. ppm at 2100°C. The maximum H2O content was about seven times larger than earlier high-temperature multi-anvil studies but significantly lower than recent laser-heated diamond anvil cell and low-temperature multi-anvil studies. We suggest that Al-free stishovite may not be a significant H2O carrier in subducting slabs, at least at the topmost lower mantle corresponding to our experimental conditions.