Ocean island basalts (OIB) exhibit significant variations in their ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ¹⁷⁶Hf/¹⁷⁷Hf, ^186,187Os/¹⁸⁸Os, and ^206,207,208Pb/²⁰⁴Pb compositions that indicate contributions from multiple mantle sources. To further constrain the relationships between diverse long-lived isotopic systems in OIB, new double-spike Pb and Hf isotope data, as well as isotope dilution highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundances are reported for nineteen Icelandic picrites and basalts for which ³He/⁴He, ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, and ^186,187Os/¹⁸⁸Os data have been reported previously (Brandon et al., 2007. GCA). Hafnium-Nd-He isotope systematics for the sample set reveal the presence of an ancient refractory source with low-³He/⁴He, while He-Pb isotope correlations indicate that recycled oceanic crustal components with high-³He/⁴He added from a less degassed mantle source are present in the Iceland plume. The highly depleted, low-³He/⁴He signature is sampled in the Northern and Western Volcanic Zones, likely due to higher degrees of partial melting at those localities enabling sampling of this refractory endmember. The ¹⁸⁷Os/¹⁸⁸Os ratios show correlations with Pb, Hf, and Nd isotope ratios indicating binary mixing between depleted and enriched sources, with no evidence for decoupling due to sulfide metasomatism. The spread of ¹⁸⁷Os/¹⁸⁸Os- ^206,207,208Pb/²⁰⁴Pb data can be explained by addition of 1–11% young recycled oceanic crust to a depleted mantle source distinct from the source of Atlantic MORB. Abundances of the HSE in Northern and Western Volcanic Zone lavas overlap with those from other OIB with similar MgO contents, showing fractionated patterns that are enriched in the more incompatible Re, Pd, and Pt over the compatible Ru, Ir, and Os. Calculated parental melt HSE abundances of those lavas also overlap with those of other OIB. Eastern Volcanic Zone lavas are highly depleted in Pt and Pd relative to other Icelandic lavas. Abundances of Pt and Pd correlate with isotopic parameters, such as ²⁰⁶Pb/²⁰⁴Pb, in Icelandic lavas, indicating that the isotopically enriched endmember sampled in the Eastern Volcanic Zone is depleted in the HSE, consistent with it being mafic in nature. The abundances of MgO in the lavas also roughly correlate with isotopic parameters, supporting the identity of the depleted endmember as ultramafic and the enriched endmember as mafic. New and previously published double-spike Pb isotope data show chiefly binary mixing with an additional component present in the vicinity of the volcano Öræfajökull. Icelandic ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb data plot below and above the majority of Mid-Atlantic Ridge basalt data, respectively, indicating that both depleted and enriched end-members in the plume have a lower U depletion age and a higher Th/U than ambient mantle. This is consistent with the enriched and depleted end-members within the Iceland plume being <2 Ga recycled oceanic crust and lithospheric mantle, respectively.