Rutile-Bearing Refractory Eclogites: Missing Link Between Continents and Depleted Mantle

• DOI: 10.1126/science.287.5451.278
• Publication Date: 2002-07-27T09:40:21Z
• Authors: Roberta L. Rudnick; Matthias Barth; Ingo Horn; William F. McDonough
• Keywords: 01 natural sciences; 0105 earth and related environmental sciences

A mass imbalance exists in Earth for Nb, Ta, and possibly Ti: continental crust depleted mantle both have subchondritic Nb/Ta, Nb/La, Ti/Zr, which requires the existence of an additional reservoir with superchondritic ratios, such as refractory eclogite produced by slab melting. Trace element compositions minerals xenolithic eclogites derived from cratonic lithospheric show that rutile dominates budget Nb Ta imparts a Ti/Zr to whole rocks. About 1 6 percent weight is required solve silicate Earth, this must concentration >/= 2 parts per million, Nb/La 1.2, Nb/Ta between 19 37-values overlap those eclogites. As lithosphere significantly lower than this, much material may reside mantle, perhaps deep core-mantle boundary.