Highly Siderophile Element and Os Isotope Results From the Structurally Atypical Batin Dunite in the Wadi Tayin Massif of the Oman Ophiolite

Dunites in ophiolites form by pyroxene dissolution and olivine precipitation during melt-peridotite interaction. We present structural geochemical data on peridotites from the Batin region (Wadi Tayin massif) of Oman ophiolite, where an exceptionally large (∼9.5 km long) dunite body was sampled ICDP Drilling Project (BA4A borehole). 900–1,200 m beneath petrological Moho, this is overlain harzburgite hosting pyroxene-depleted pyroxene-rich bands. Highly siderophile elements (HSEs) Os isotopes, excellent tracers melt flow through peridotites, were measured dunites interspersed harzburgites BA4A borehole. The structurally chemically distinct Moho Transition Zone basal section resembling instead sparse veins main mantle section. have fairly uniform Os, Ir, Ru abundances, but Pd Pt contents increasing with depth. One deep sample has initial 187Os/188Os more radiogenic than MORB. Though limited number demands prudence, we suggest that formed a pulse melts, whose impeded ∼1,200 below Moho. As these melts ascended, they may lost their character relative enrichment interaction which much higher HSE melts. Such would also diminish under-saturation eliminating capacity to sufficiently dissolve host dunite, thus explaining upper limit at ∼900 m.