Neoproterozoic Ophiolites of the Arabian-Nubian Shield

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

“…Primary Cr-spinel relics are found in all the lithologic varieties of altered ultramafic samples at Bir Umq. In the serpentinized samples, as in the mantle sections of many other J o u r n a l P r e -p r o o f ophiolitic occurrences in the ANS (Shahien et al, 2021), Cr-spinel is altered to ferritchromite and Cr-magnetite along cracks and around the crystal boundaries. This is a post-magmatic alteration process that reflects fluid ingress along cracks and through the intergranular medium.…”

“…These rocks have been assigned by various authors to every oceanic geodynamic setting, including mid-ocean ridge and supra-subduction zone settings (Ahmed et al, 2012;Habtoor et al, 2017). More recently, it has become a clear consensus view that all the Arabian Shield ophiolites formed in supra-subduction settings (Shahien et al, 2021), and attention has turned to resolving whether they represent back-arc or fore-arc spreading centers. There is considerable support for a fore-arc tectonic setting for all these ophiolites, based on whole-rock chemistry of serpentinite and the compositions of fresh relics of mafic minerals in the mantle sections (Abuamarah et al, 2020;Gahlan et al, 2021).…”