Implications of a two-component marble-cake mantle

It is suggested that the upper mantle contains elongated strips of subducted oceanic lithosphere. These strips are stretched and thinned by the normal and shear strains in the convecting mantle, and are destroyed by being reprocessed at ocean ridges or, on the centimetre scale, by dissolution processes; the result is a marble-cake mantle. Simple theoretical calculations, together with isotopic and structural observations made on high-temperature peridotite massifs, lead to a comprehensive marble-cake model which is consistent with most isotopic and mechanical constraints.