A search for142Nd evidence of primordial mantle heterogeneities in plume basalts

In order to assess whether material differentiated shortly after terrestrial accretion is still present in the deep mantle, we investigated hot spot basalts for142Nd/144Nd anomalies that could attest for the presence of live146Sm (T1/2= 103 My) at the time the mantle source of these basalts formed. We analyzed high3He/4He basalts from Loihi and Ethiopia and normal3He/4He basalts from Iceland. Although the143Nd/144Nd ratios of these basalts reflect a source with long‐term LREE (light rare earth elements) depletion, no resolvable142Nd anomalies were detected. Taking the analytical uncertainties (10–20 ppm) into account, however, the present results do not rule out the possibility that a large proportion of material fractionated very early in the Earth's history may still be hidden in the deep mantle.