The 40Ar‐39Ar analyses of 28 groundmass separates from volcanic rocks from the islands of Santiago, Sal, and São Vicente, Cape Verde archipelago, are presented. The new age data record the volcanic evolution for Santiago from 4.6 to 0.7 Ma, for Sal from around 15 to 1.1 Ma, and for São Vicente from 6.6 to 0.3 Ma. The major submarine constructional phase of Santiago was erupted within a few hundred thousand years interval around 4.6 Ma. Most of the subaerial Santiago volcanic rocks were erupted in a second episode from 3.3 to 2.2 Ma and late volcanism occurred at 1.1–0.7 Ma. Volcanism on Sal evolved in five stages: (1) poorly constrained early Miocene activity, (2) 16–14 Ma, (3) 12–8 Ma, (4) around 5.4 Ma, and (5) 1.1–0.6 Ma. São Vicente was constructed during three active periods: (1) >6.6–5.9 Ma, (2) 4.7–4.5 Ma, and (3) ∼0.3 Ma. Sr isotope analyses of carbonates from Maio confirm an Early Cretaceous age for limestones deposited on the seafloor and later uplifted. The Cape Verde Rise is indicated to have fully formed in the early Miocene around 22 Ma, accompanied by the initial alkaline volcanism. Considerable volcanism on Sal, Boa Vista, and Maio took place in the Miocene and Pliocene and extended over much larger areas than the present islands, whereas volcanism of the southwestern and northwestern island groups developed mainly during the Pliocene and Pleistocene and was mostly confined to the present island areas. The periods of volcanic activity may be broadly correlated between the northwestern and southwestern groups of islands. Young volcanism (0.3–0.1 Ma) throughout the northwestern group extends along a 150 km long NW‐SE trending lineament. A relatively moderate average melting rate for the hot spot over the 22 Ma period is estimated at ∼0.026 km3/a, corresponding to a total volume of 570 × 103 km3 of magma emplaced in the crust and a mantle volume flux of 28 m3/s, much lower than Iceland or Hawaii. The archipelago is situated to the south and SW of the center of the mantle plume anomaly and ahead of its relative movement. The timing and location of volcanism suggest that mantle melting takes place in three channels, an eastern one that has been active for 22 Ma and in southwestern and northwestern channels since late Miocene.

We present compositional data on a suite of 18 primitive neovolcanic alkali basalts from three flank zone regions in Iceland (Vestmannaeyjar in the south, Snaefell in the east, and Snaefellsnes in the west) that are peripheral to the main rift zones that are dominated by tholeiitic basalts. This study integrates He isotope data with radiogenic isotope data (Sr-Nd-Pb-Hf), stable isotope data (δ 18 O), and trace element data to characterise the compositional features of the trace-elementenriched components of the Icelandic mantle. We also present high-precision Pb isotope data on an additional 57 lava samples from the flank zones (including Öraefajökull in the southeast) and the Northern and Eastern rift zones. Most Icelandic lavas have negative ∆ 207 Pb (-4 to-1), with higher values (-1 to +4) found only in samples from Öraefajökull, Snaefell, and parts of the Reykjanes Peninsula. At Snaefell, this EM1-type component is characterised by a low δ 18 O olivine signature (+4.1‰ to +4.6‰), moderate 206 Pb/ 204 Pb values (18.4-18.6) and MORB-like 3 He/ 4 He (6.9-7.5 R/R A). Samples from Vestmannaeyjar and Snaefellsnes have mantle-like δ 18 O olivine (+4.9‰ to +5.0‰), and radiogenic 206 Pb/ 204 Pb values (18.9-19.3) that fall on the NHRL for 208 Pb/ 204 Pb (∆ 208 Pb-5 to +5). Compared to the Vestmannaeyjar lavas, Snaefellsnes lavas have higher La/Yb N (5-11 vs. 3-5), lower ε Nd (5.5-6.5 vs. 6.8-7.6) and lower 3 He/ 4 He (6.3-8.6 R/R A vs. 11.4-13.5 R/R A). Therefore, the most trace element enriched components in the Icelandic mantle are not the carriers of the high 3 He/ 4 He values (> 15 R/R A) found in some lavas on Iceland and the adjacent ridges, and instead are consistent with degassed, recycled components. Even after excluding the EM1-type high ∆ 207 Pb samples, high-precision Pb isotope data produce a kinked array on an 206 Pb/ 204 Pb vs. 208 Pb/ 204 Pb plot, which is not consistent with simple binary mixing between two end-members. This requires significant lateral heterogeneity within the Icelandic mantle and the presence of more than just two compositionally-distinct local mixing end-member components. Samples from each of the main axial rift zones define different trends. Despite the tectonic continuity between the Northern Volcanic Zone and the Eastern Volcanic Zone, lavas from these two rift zones define separate sub-parallel linear arrays. Lavas from the adjacent Western Volcanic Zone and the Eastern Volcanic Zone define oblique linear arrays that converge on a common local end-member that is not involved in the magmatism of the Northern Volcanic Zone. Therefore, there is a distinct NE-SW compositional heterogeneity within the Icelandic mantle.

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