Mantle heterogeneity beneath the Phoenix ridge in the Drake Passage, Antarctica

Abstract

We determined Sr, Nd and Pb isotopic compositions for basalts recovered from the fossilized Phoenix Ridge in the Drake Passage, Antarctica, in order to understand the nature of sub-ridge mantle source. We observe that small scale isotopic heterogeneity does exist at shallow level in the sub-axial mantle of the Phoenix Ridge, being distant from any known hotspots. Extinction of the Phoenix Ridge is likely to lead decreasing extent of partial melting in this region. We interpret that geochemically enriched materials dispersed in ambient depleted mantle were the first fraction to melt for generating the studied enriched mid-ocean ridge basalts (E-MORB) represented by relatively small extents of melt of enriched mantle source