Finally, the isotopic signature of the tholeiitic and K-Na-alkaline-magmatism from the PAE in general, and from ASV in particular, may reflect ancient heterogeneities preserved in the subcontinental lithospheric mantle
. As matter of fact, all the geochemical data indicate that the PAE magmatism requires heterogeneous mantle sources, also in terms of radiogenic isotopes [6,10]: such heterogeneities probably represent metasomatic processes which have occurred mainly at 0.5-1.0 Ga and at 1.5-2.0 Ga (cf.
Alternatively, EM1 sources may bear an imprint from subducted pelagic sediment subduction (Weaver, 1991) or represent subcontinental lithospheric mantle
scraped from beneath continents (e.g., Milner and le Roex, 1996).