The composition of the lower oceanic crust in the Wadi Khafifah section of the southern Samail (Oman) ophiolite

The composition of the intrusive gabbroic lower oceanic crust remains poorly characterized in comparison to the extrusive portion of the oceanic crust, especially for intermediate-fast spreading mid-ocean ridges. This is a consequence of limited exposures of extant lower oceanic crust and of ophiolites similar to mid-ocean ridge crust. One of the best analogues for mid-ocean ridge crust is the southern Samail ophiolite that formed during a period of rapid seafloor spreading above a nascent subduction zone. Here, we focus on the geochemical stratigraphy (whole rock and mineral major and trace element compositions) of the 5200 m-thick, lower crustal, Wadi Khafifah section of the Wadin Tayin massif in the southern Oman ophiolite. Gabbros from the lowermost 3700 m of this section (the 'lower gabbros') show no systematic changes in composition with height above the Mantle Transition Zone. In contrast, gabbros from the uppermost 1500 m (the 'upper gabbros') display marked increases in incompa...