Garnet-perovskite transformation in hydrous MORB system.

Abstract

Resent tomographic observations suggest that some subductig slabs stagnate at mantle transition zone. Irifune and Ringwood (1978) show that there is density crossover occurs at the depth 660km to 800km between MORB and peridotite, which causes buoyancy and stagnate slab or tear off upper oceanic crust at 660km. It is important to determine the depth of post-garnet transition occurs in MORB system to discuss the behavior of the slab at 660 km. In this study, we determined post-garnet phase boundary in MORB system using in-situ X-ray experiment at 20-25GPa and 1100-1200 ºC under hydrous conditions.