View article

In this paper we re‐examine the relationship between seismically constrained variations in crustal structure along the southern East Pacific Rise (SEPR) and the segment‐scale variations in axial depth, morphology, basalt geochemistry, and hydrothermal activity that have often been attributed to along‐axis differences in the supply of magma to the mid‐ocean ridge. Along >800 km of the fast spreading SEPR, good correlations exist between axial depth, ridge cross‐sectional area, mantle Bouguer anomaly, and the MgO weight percent of basalts recovered from the rise axis. These correlations indicate along‐axis changes in crustal thickness and temperature consistent with variations in magma supply on time scales of ∼100,000 years. In contrast, we show that the depth and width of the midcrustal magma sill, the thickness of seismic layer 2A, and the intensity of hydrothermal venting are poorly correlated with …