An iron isotopic perspective for the material flow from off-axis mantle plume to mid-ocean ridge system

Abstract

The interaction between the mid-oceanic ridge (MOR) and the mantle plume is a crucial aspect for understanding Earth’s internal works. However, the compositions and styles of material flow from off-axis plumes to the MOR system still remains elusive. This study examined the iron (Fe) isotope composition of basalts from the South Mid-Atlantic Ridge (SMAR) for the first time. The results showed a consistent relationship between the Fe isotope compositions, trace element ratios, and traditional radiogenic isotopic compositions of lavas from the SMAR and the off-axis Saint Helena plume. This suggests that variations in the Fe isotope compositions of the SMAR mantle source may be influenced by the contribution of the Saint Helena plume. We propose that heavy-Fe pyroxenites are widely distributed within the lithosphere-asthenosphere boundary (LAB) layer in the region between the plume and ridge. These plume-related pyroxenites can transport plume signatures with heavy Fe isotopic compositions into the MOR system at the LAB level.