“…Nd and 176 Hf/ 177 Hf ratios in high 3 He/ 4 He lavas [e.g., Caro and Bourdon, 2010;Jackson et al, 2010] suggest a history of depletion by melt extraction, a process that increases the Lu/Hf and Sm/Nd ratios in the meltdepleted residue. The association of primitive noble gas isotopic signatures in a mantle reservoir with distinctly nonchondritic refractory element radiogenic isotopic signatures is a paradox that has been the subject of considerable discussion [e.g., Kurz et al, 1982;Hart et al, 1992;Class and Goldstein, 2005;Parman et al, 2005;Caro et al, 2008;Carlson and Boyet, 2008;Gonnermann and Mukhopadhyay, 2009;Caro and Bourdon, 2010;Jackson et al, 2010;Jackson and Carlson, 2011].…”