Tracing material contributions from Saint Helena plume to the South Mid-Atlantic ridge system

The spatial scope of the Saint Helena hotspot influence on SMAR system is from SMAR 14.2°S to 20.8°S segments bounded by Cardno T.F. and Trinidade T.F. The sublithospheric flow channels between Saint Helena plume and the northern segments (e.g., segment 2) could be continuous, while those at the southern segments (e.g., segments 4–5) change to be more schlieren-like. Possible flow directions of the Saint Helena hotspot materials from Cardno seamount toward the SMAR system are inferred. The ends of the inferred flows directions are at the SMAR segments 2–5, where the basalts have stronger Saint Helena plume-related geochemical signals, and the ridge axes keep shallower axial depth and lower mantle Bouguer gravity anomaly relative to the other segments. Following the possible directions, the lateral footprint of the asthenospheric mantle influenced by the Saint Helena plume has grown to several hundreds of kilometers over the past 80 Ma.