Electron Backscatter Diffraction (EBSD) analysis through fast-spread lower oceanic crust of Wadi Gideah in the Oman ophiolite

The microstructural data presented here were obtained from a reference profile which we established along the lower oceanic crust of Wadi Gideah in the Oman ophiolite (Wadi Tayin Massif; e.g., Nicolas et al., 2000). The Oman ophiolite is widely regarded as the best-preserved analogue of fast-spread oceanic crust on land, and therefore provides an ideal natural laboratory for investigating accretion processes beneath fast-spreading mid-ocean ridges. Our data set contains 68 samples from the axial melt lens down to the mantle transition zone with an average spacing of 81 m between two samples. This extensive data set provides insights into mechanical processes during crustal accretion. The data focuses on the three major primary phases plagioclase, clinopyroxene and olivine. The latter shows significant serpentinization such that the former two provide a much better continuity along the crust. The varitextured and foliated gabbros reveal significantly finer grain sizes in plagioclase and clinopyroxene than the layered gabbros. The fabric strength quantified by the ODF J index of both phases is generally low in the upper 1500 meters and increases gradually down section with significant scattering below 3500 meters above the Moho. The lowermost 1000 meters reveal a decreasing fabric strength. Misorientation in plagioclase and clinopyroxene grains shows a similar trend whereas misorientation in olivine is generally stronger and more scattered along the crust. The BA index, quantifying the pole figure symmetry of plagioclase with 0 for a purely foliated and 1 for a purely lineated fabric, shows intermediate symmetries with a significant lineation in the upper 1500 m before it shifts towards nearly purely foliated symmetries between 3500 and 2700 meters above the Moho. Below 2700 meters, the lineation component increases down section copying the scattering of the ODF J index.