OSMIUM RECYCLING IN SUBDUCTION ZONES

Peridotite xenoliths from the Cascade arc in the United States and in the Japan arc have neodymium and osmium isotopic compositions that are consistent with addition of 5 to 15 percent of subducted material to the present-day depleted mantle. These observations suggest that osmiu m can be partitioned into oxidized and chlorine-rich slab-derived flui ds or melts. These results place new constraints on the behavior of os mium (and possibly other platinum group elements) during subduction of oceanic crust by showing that osmium can be transported into the mant le wedge.