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Shield-stage high-MgO alkalic lavas from La Palma and El Hierro (Canary Islands) have been characterized for their O–Sr–Nd–Os–Pb isotope compositions and major-, trace-, and highly siderophile-element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundances. New data are also reported for associated evolved rocks, and entrained xenoliths. Clear differences in Pd/Ir and isotopic ratios for high Os (>50ppt) lavas from El Hierro (δ¹⁸O_olivine=5.17±0.08‰; ⁸⁷Sr/⁸⁶Sr=0.7029 to 0.7031; ε_Nd=+5.7 to +7.1; ¹⁸⁷Os/¹⁸⁸Os=0.1481 to 0.1750; ²⁰⁶Pb/²⁰⁴Pb=19.1 to 19.7; Pd/Ir=6±3) versus those from La Palma (δ¹⁸O_olivine=4.87±0.18‰; ⁸⁷Sr/⁸⁶Sr=0.7031 to 0.7032; ε_Nd=+5.0 to +6.4; ¹⁸⁷Os/¹⁸⁸Os=0.1421 to 0.1460; ²⁰⁶Pb/²⁰⁴Pb=19.5 to 20.2; Pd/Ir=11±4) are revealed from the dataset. Crustal or lithospheric assimilation during magma transport cannot explain variations in isotopic ratios or element abundances of the lavas. Shallow …