Petrogenesis of the crustal section of the Neoproterozoic Jabal Wask ophiolite-arc complex, Midyan terrane, NW Arabian Shield: Extension of the Jabal Ess complex

The Jabal Wask ophiolite arc complex (JWOA) comprises forearc basalt (FAB) and boninite (gabbro) that range from MORB- and Izu Bonin Marianas forearc basalt (IBM FAB)-like to volcanic arc basalt-like. Other mafic rocks are transitional to alkaline lavas and intrusives. More evolved basaltic andesite and predominant andesite lavas, dykes and gabbros are also present. Other rock types include high-Mg andesite (HMA), low-Si boninite (LSB), high-Si boninite (HSB) and rhyolite and granite of volcanic arc granite (VAG) affinity. Though the FAB and boninite have major oxide compositional characteristics largely similar to MORB and IBM FAB, these mafic rocks exhibit high field strength element (HFSE) concentrations that are similar to IBM FAB and range to much lower than MORB. For example, whereby Jabal Wask FAB, HMA and BON have concentrations of Ce, Yb and Zr of 0.74–42.5 µg/g, 0.62–5.63 µg/g and 4.5–141.5 µg/g, MORB exhibit mean Ce, Yb, and Zr of 15.48 µg/g, 3.10 µg/g and 103.90 µg/g.We posit that the Jabal Wask ophiolite represents a southern extension of the Jabal Ess ophiolite and formed according to the subduction initiation rule (i.e., MORB-like lavas followed by HMA, LSB and HSB).