Microstructures from the Lower Crust of the Josephine Ophiolite

Typical microstructures from the lower crust of the Josephine ophiolite.

Close-up of hypersolidus foliation from the gabbros of the Josephine ophiolite. Plagioclase laths are ~ 2 mm long. Hypersolidus fabrics are preserved throughout the ophiolite and record deformation in the presence of melt. Evidence for dislocation creep and other mechanisms of plastic deformation are not observed in the lower crust. Such relationships have also been observed in the Oman, Troodos, and Tortuga ophiolites and cores from Hess Deep (near the East Pacific Rise) and are in contrast to observations from slow-spreading centers such as the Mid-Atlantic Ridge (ODP Leg 153) and the Southwest Indian Ridge (ODP Legs 118/176).