Water contents of Al-bearing minerals in the mantle transition zone and the lower mantle

Abstract

Water contents of Al-bearing minerals in the mantle transition zone and the lower mantle were determined in the systems pyrope - enstatite with H2O of 11.3 wt% and 18.7 wt% at pressures of 20-26 GPa and temperatures of 1473-1873K. The water contents of Al-bearing experimental products were measured by secondary ion mass spectrometry (SIMS) in Hokkaido University, and found the water contents as follows : perovskite ∼0.8 wt%, garnet ∼0.6 wt%, stishovite ∼1.4 wt%, phase D ∼22 wt%. These water contents were strongly related to the Al contents of these phases. Thus the water contents in the Earth' s mantle minerals are strongly related to the Al contents.