Water delivered to the mantle by aluminum enriched hydrated slabs?

Dense hydrous magnesium silicates (DHMSs) are generally considered as primary water carriers from the shallow lithosphere to the deep mantle transition region (MTR; 410–660 km in depth). Among DHMSs, Superhydrous phase B (hereafter, SuB) holds the chemical formula, Mg10Si3H3O18.