Nonchondritic Nd-142 in suboceanic mantle peridotites

The discovery that several solid Earth reservoirs have a superchondritic Nd-142/Nd-144 ratio led to the hypothesis that either the bulk silicate Earth is not chondritic or that a subchondritic reservoir lies hidden somewhere within the Earth's interior. One important reservoir, i.e., mid-ocean ridge peridotites representing the main component of the upper oceanic mantle and the source of mid-ocean ridge basalt, has never been tested for Nd-142/Nd-144. We determined the Nd-142/Nd-144 ratio in clinopyroxene separated from two peridotites and a pyroxenite from the SW Indian Ridge and one peridotite from the northern Mid-Atlantic Ridge. All samples analyzed have superchondritic Nd-142/Nd-144 ratios in line with mantle-derived material measured to date, except for some ancient cratonic rocks.