Mantle source heterogeneity in a Neoproterozoic back-arc basin: Geochemical and thermodynamic modeling of the volcanic section of Wadi Ghadir ophiolite, Egypt

Wadi Ghadir ophiolite in the Egyptian Eastern Desert, which forms northern part of Nubian Shield, is considered as one best-preserved segments Neoproterozoic oceanic lithosphere on Earth. Primary melt calculations and thermodynamic modeling new geochemical data for pillow lavas dike complexes, integrated with comprehensive petrographic investigations, are here employed to unravel geodynamic evolution this ophiolitic section. Whole-rock clinopyroxene indicate that sheeted complexes preserve signatures N-MORB, E-MORB OIB-like basalts. Less abundant, discrete dikes have a distinctly LILE-enriched island arc tholeiite (IAT) composition. The replicate mixed liquid lines descent, whereas exhibit calc-alkaline differentiation trend. were produced by limited (5–7%) mantle partial melting result isothermal decompression over wide pressure range (5 – 19 kbar) restricted potential temperatures (Tp ≈ 1260–1300 °C), suggesting ponding rising melts from depths ∼60 15 km dry mantle. 9–11% at P 9.7 ± 2.5 kbar, Tp 1290 °C, 14.7 1.4 1325 role varying hydrostatic pressure. magma source occurred 10.7 0.6 kbar 1230–1300 °C 11–13% metasomatized region. calculated ranges different consistently lower than sub-ridge ambient Together variable concentrations K2O other incompatible elements, estimated low generation emphasize sources wet peridotite melting. modeled primary designate crustal growth during back‐arc basin opening closure. During opening, mildly enriched high-Ti tholeiitic (pillow lavas) transitional (sheeted complexes) melts, subduction initiation closure promoted melt-peridotite interaction. Lowering solidus subduction-related components triggered spinel lherzolitic low-Ti sourced dikes. MORB SSZ characteristics studied volcanic rocks, coupled various lack significant thermal anomalies conditions, interpreted manifestations heterogeneity marginal accretionary stages Arabian-Nubian Shield.