New insights on Madeira-Tore Rise post-Atlantic breakup magmatism: Sr-Nd-Hf-Pb isotopes and 40Ar/39Ar ages of Rugoso, Jo Cousin, and Pico Pia seamounts

The Central East Atlantic Ocean and its Iberian and Moroccan margins have been affected by intense magmatic activity from the Cretaceous onward. In this study, we present new major and trace element, isotopic (Sr-Nd-Hf-Pb), and geochronological ( 40 Ar/ 39 Ar) data for three seamounts (Rugoso, Jo Cousin, and Pico Pia) located on top of the Madeira-Tore Rise (MTR), a major ∼1000 km long physiographic feature in the Central East Atlantic Ocean. The alkaline composition of these volcanoes and their ages (0.07–1.39 Ma) contrast with the mid-ocean ridge basalt (MORB) affinity and the ∼125–130 Ma age of the underlying ridge. This defines the MTR as a complex structure, initially formed during the Atlantic breakup and later overprinted by intraplate magmatism. The reported seamounts are distinct with respect to their degrees of SiO 2 -undersaturation (Jo Cousin being the least undersaturated) and magma evolution (reaching phonolitic compositions in Rugoso). Additionally, the studied lavas further increase the range of isotopic signatures previously observed for the post-breakup MTR volcanoes, reflecting their derivation from sources either with more time-integrated depletion (Jo Cousin: ε Nd up to 10.27 and 206 Pb/ 204 Pb down to 18.427) or enrichment (Rugoso and Pico Pia: ε Nd down to 4.26 and 206 Pb/ 204 Pb up to 20.256) in the most incompatible elements. These signatures can be interpreted in terms of the roles of HIMU and DMM mantle components, as well as different proportions of eclogite/pyroxenite and peridotite mantle lithologies in the magma sources. Despite their similar ages and geographic proximity, Rugoso, Jo Cousin, and Pico Pia seamounts exhibit dual isotopic compositions, with Jo Cousin showing affinities with the Madeira Archipelago, and Rugoso and Pico Pia being isotopically comparable to lavas from the Canary Archipelago. However, considering their ages and geographic positions, these volcanic structures cannot be directly attributed to the activity of mantle plumes at the origin of such hotspot provinces. Instead, we propose that they were produced by independent, small-scale, and ephemeral secondary mantle upwellings that sampled compositional domains similar to those feeding the Madeira and Canary provinces within the Central East Atlantic Anomaly (CEAA), located at the topmost lower mantle. • The studied intraplate seamounts are superimposed on the Madeira-Tore Rise (MTR). • These alkaline lavas expand the isotopic range of intraplate magmatism in MTR. • Isotopic (Sr-Nd-Hf-Pb) data show affinities with Madeira or Canary hotspot provinces. • Magmas link to small, short-lived upwellings from the Central East Atlantic Anomaly. • HIMU-like component and mantle eclogites/pyroxenites are key to magma composition.