Description: As largest and best-exposed paleo-fast-spread oceanic crust on land, the Samail ophiolite in the Sultanate of Oman represents an ideal natural laboratory for investigating processes at fast-spreading mid-ocean ridges. We studied a layered gabbro sequence from the middle of the plutonic crust showing dm-scale modal layering with olivine abundance gradually decreasing from layer base to top (Wadi Somerah, Sumail block). Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was performed in order to obtain trace element contents and rare earth elements (REE) in particular. Analyses were performed at the Institut für Geowissenschaften (Christian-Albrechts-Universität zu Kiel, Germany) using a 193 nm ArF excimer laser ablation system (GeoLasPro HD, Coherent) coupled to an Agilent 7900s ICP-MS. Analyses were performed as point measurements with 16 Hz pulse rate, 18 Jcm-2 fluence and a crater diameter of 120 µm on plagioclase, and 10 Hz, 12 Jcm-2 and a crater diameter of 32 µm on clinopyroxene. Differences in core and rim compositions of clinopyroxene reveal significant zonation with higher REE contents in the rim. Crystallization temperatures calculated using the REE-thermometer of Sun and Liang (2017; doi:10.1007/s00410-016-1326-9) vary between 1230 and 1300°C.

Description: 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.