Pacific lower crustal and shallow mantle sections recovered

Abstract

During Leg 147 of the Ocean Drilling Program, sections of the lower crust and shallow mantle generated at a fast‐spreading mid‐ocean ridge were recovered for the first time. Taking advantage of a tectonic window into the Earth's lithosphere in the equatorial Pacific, two sites were cored to gain an understanding of how the oceanic crust is built in an environment with a high rate of magma supply and to investigate the interaction between magmatic, hydrothermal, and tectonic processes in this setting. At the first site, an exposure of plutonic rocks was cored to investigate magma‐chamber processes and the interaction of deformation and fluid flow in the lower crust. The second series of holes was positioned within the transition zone between the magmatic crust and shallow mantle, in the vicinity of the Mohorovicic discontinuity, or Mono, to document the nature of the residual mantle beneath fast‐spreading ridges and to investigate the migration of melt from the mantle to the crust.