A Dual‐Level Magmatic System Beneath the East Pacific Rise, 9°N

Abstract

AbstractData from three co‐located wide‐angle ocean‐bottom seismograph experiments were used to make a new two‐dimensional tomographic image of the East Pacific Rise at 9°N. The upper half of the crustal magmatic system has a different seismic structure than the lower half, presumably corresponding with differences in melt storage and crustal cooling. The upper region is narrow (∼4.5 km wide at 2–3 km depth bsf) and estimated to contain higher melt fractions; the lower region broadens with depth and contains lower melt fractions. The shape of the system suggests steeply‐dipping isotherms and relatively stronger hydrothermal circulation in the upper gabbroic section of the crust, with moderately flattening isotherms and less circulation in the lower gabbroic section.