Epidosite in ophiolitic rocks of the Arabian-Nubian Shield: Implications from remote sensing, ore mineralogy, petrology, and geochemistry

Abstract

Epidotization is a fundamental hydrothermal process in oceanic lithosphere, yet its manifestation, geochemical fingerprints, and mineralization potential within the Neoproterozoic Arabian-Nubian Shield (ANS) remain poorly constrained. This study documents newly identified epidosite bodies hosted within ophiolitic metagabbros at Wadi Zayatit, South Eastern Desert, Egypt—the first such recorded occurrence in the ANS. An integrated approach combining PRISMA hyperspectral remote sensing (SMACC algorithm), ASTER/Sentinel-2 data, field mapping, petrography, XRF geochemistry, XRD, and SEM-EDX ore microscopy was employed. Geochemically, the protoliths exhibit low-Ti, high-Mg back-arc tholeiitic affinities, whereas the epidosites display pronounced hydrothermal signatures: extreme CaO enrichment (20.9-25.9 wt.%), significant depletion in SiO 2 , MgO, Na 2 O, and K 2 O (low AI, high CCPI), and base metal (Zn, Pb, Cu) loss coupled with Sr/V gains, as quantified by isocon analysis. Ore microscopy, XRD, and SEM-EDX further reveal extensive oxidation-exsolution of primary magmatic titanomagnetite into Ti-poor magnetite and ilmenite, indicating high-oxygen-fugacity fluid-rock interaction under greenschist- to lower amphibolite-facies conditions (∼450–500 °C, 2–4 kbar). Collectively, these findings establish the Wadi Zayatit epidosites as fossilized hydrothermal up-flow zones within the ANS, offering critical insights into Ca-metasomatic mass transfer during Neoproterozoic subduction-accretion tectonics. Furthermore, the associated Fe-Ti oxide mineralization and base metal depletion identify these metasomatized zones as prospective metal-source regions for volcanogenic massive sulfide (VMS)-type systems, providing new exploration targets in the Egyptian Eastern Desert.