Os isotope systematics in Fogo Island: Evidence for lower continental crust fragments under the Cape Verde Southern Islands

As with Pb, Sr and He, the Os and Nd isotopic compositions of the moderate HIMU end-member are explained by the mixing of 1.6 Ga recycled oceanic crust (ROC) and lower mantle material (LM) and interpreted to represent the Cape Verde mantle plume expression. For the EM1-like end-member, the high 187Os / 188Os ratios that are measured in mafic lavas preclude the sub-continental lithospheric mantle from being its origin, as previously proposed based on trace element and Pb, Sr and Nd isotopic compositions. Our new isotopic and trace element data still indicate that the enriched component is related to continental lithospheric material incorporated in the oceanic lithosphere during the opening of the Atlantic Ocean but requires the involvement of lower continental crust fragments.