A search for 142Nd evidence of primordial mantle heterogeneities in plume basalts

Abstract

In order to assess whether material differentiated shortly after terrestrial accretion is still present in the deep mantle, we investigated hot spot basalts for 142Nd/144Nd anomalies that could attest for the presence of live 146Sm (T1/2 = 103 My) at the time the mantle source of-these basalts formed. We analyzed high 3He/4He basalts from Loihi and Ethiopia and normal 3He/4He basalts from Iceland. Although the 143Nd/144Nd ratios of these basalts reflect a source with long-term LREE (light rare earth elements) depletion, no resolvable 142Nd 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 dee mantle. Copyright 2005 by the American Geophysical Union.