Formation of gold-bearing listvenite in the mantle section of the Neoproterozoic Bir Umq ophiolite, Western Arabian Shield, Saudi Arabia

Serpentinized peridotite and associated listvenites of Neoproterozoic age outcrop in the Bir Umq area western Saudi Arabia. The mantle section ophiolite is extensively serpentinized. Serpentinite host samples are low Al2O3 (0.48–0.75 wt%) CaO (0.28–1.24 have high Mg# (0.90–0.92), indicating a strongly depleted protolith, typically with supra-subduction zone environments more specifically fore-arc settings. Listvenite bodies various shapes sizes developed by alteration serpentinite. Listvenites occupy hanging walls stack thrust faults, while serpentinite dominates footwalls. Based on mineralogical composition whole-rock geochemistry, distinguished into carbonate listvenite silica-carbonate listvenite; latter further divided mineralized non-mineralized samples. Carbonate MgO, Fe2O3, CaO, but SiO2. Silica-carbonate characterized presence rhythmic banding quartz minerals fuchsite. preserve stages progressive metasomatic transformation their ultramafic protoliths due to interaction hydrothermal fluids enriched CO2, SiO2, Au, K, other fluid-mobile elements. association thrusting suggests that faults acted as conduits for derived from metamorphism underlying units during subduction obduction. Schistosity deformation fabrics imply initial listvenitization took place at conditions similar serpentinization. On hand, absence it postdates serpentinization therefore represents separate later fluid infiltration event. Finally, highly elements Zn, Pb, Cu, Ag, most notably Au; this enrichment not correlated silica content. This yet third event responsible mineralization Au enrichment. concentrations 0.84–2.31 ng g?1 serpentinite, 26–403 listvenite, 152–545 2286–3712 listvenite.