The influence of small-scale mantle heterogeneities on Mid-Ocean Ridge volcanism: Evidence from the southern Mid-Atlantic Ridge (7°30′S to 11°30′S) and Ascension Island

Volcanism along Mid-Ocean Ridges is known to exhibit significant isotopic and elemental variations, traditionally regarded as reflecting global scale variations in mantle depletion history and refertilization processes. The ∼400km long Mid-Atlantic Ridge (MAR) between the Ascension and Bode Verde Fracture Zones (7°30′S to 11°30′S) has been sampled at high spatial resolution (c. 10km along-axis scale) and large elemental and isotopic variations have been identified covering almost the entire compositional spectrum of MAR basalts. In this paper we employ a multi-isotope (Sr–Nd–Hf–Pb) and trace element approach in order to explore the geodynamic implications of along-ridge compositional variations and their relationship to off-axis volcanism on nearby Ascension Island, commonly regarded as plume-related.