Korab Kansi and Abu Dahr Neoproterozoic ophiolitic peridotites in the Southern Eastern Desert (SED) of Egypt, are parts of the largest ophiolitic nappes in the Arabian-Nubian Shield. They mainly comprise refractory harzburgites with minor dunites that are commonly altered to serpentinites and talc carbonates. Olivine relics in serpentinized peridotites of the two complexes have olivines with high forsterite (Fo90.6-92.2) and NiO (0.39 wt%) and low MnO (0. 13 wt%) contents, similar to those of mantle olivines. High Mg# (0.91–0.95) of orthopyroxene is consistent with that of depleted harzburgites. Primary spinel Cr# (0.55–0.75) and TiO2 contents (<0.04 wt%) of the two peridotite complexes are similar to forearc peridotite spinels. The estimated degree of partial melting of Korab Kansi peridotites (25–40% melting) is slightly lower than that of Abu Dahr (30–40% melting), consistent with modern forearc peridotites. Korab Kansi peridotites exhibit lower oxygen fugacity (Δlog ƒO2, FMQ + 0.7 on average) and equilibrium temperature (610–710 °C) than those of Abu Dahr (T, 750–900 °C at Δlog ƒO2, FMQ + 2.1), both suggesting subduction-modified peridotites. The low concentrations of incompatible elements, U-shaped REE patterns and high spinel Cr# of both peridotites indicate highly depleted mantle protoliths, reflecting multiple metasomatic and melting episodes in the mantle wedge. Enrichment of fluid mobile elements (e.g. B, Li, Th, U, Pb) relative to high-field strength elements (e.g. Nb, Ta, Ti, Zr) may reflect interaction between slab-derived fluids and peridotites. Calculated parental melts in equilibrium with Korab Kansi and Abu Dahr peridotite spinels have tholeiitic (MORB-like) and boninitic affinities, which were generated during proto-forearc spreading to a mature arc stage. Variations in melt compositions suggest a transitional setting from early proto-forearc spreading of mantle beneath Korab Kansi to the mature arc stage of Abu Dahr peridotites. Subduction initiation possibly started in the W and/or SW with proto-forearc spreading, and progressed to the E and/or NE where a mature arc stage with boninitic melts above an E- and/or SE-dipping subduction zone.