Sr-Nd-Pb isotope ratios, geochemical compositions, and Ar-40/Ar-39 data oflavas from San Felix Island (Southeast Pacific): Implications for magma genesis and sources

We present the first trace element and age data combined with new Sr, Nd, a nd Pb isotope ratios on lavas from San Felix Island in the Southeast Pacifi c. A Ar-40/Ar-39 plateau age of 421 +/- 18 ka implies young intraplate volc anic activity in this region relative to the similar to 22 Ma old volcanism on the neighbouring Easter seamount chain (ESC). The incompatible element compositions of the San Felix magmas are similar to those of EM1-type basal ts from Gough, although the isotopic compositions differ. San Felix formed some 20 Ma after the ESC plume affected the plate in this region but no che mical signature of the ESC material is observed in the young volcanic rocks . The composition of the San Felix basalts indicates a mantle source contai ning old continental lithospheric material from either metasomatized mantle or recycled sediments, which ascends in a weak mantle plume.