Geochemical and remote sensing insights into the hydrothermal origin of Banded Iron Formations at the Fatira Site, Northern Egyptian Nubian Shield

Abstract

This study combines remote sensing, geochemical data, mineralogical analyses, and field investigations to examine the hydrothermal origin of the Banded Iron Formations (BIFs) in the Fatira region of the Egyptian Nubian Shield. The BIFs are situated within sheared metavolcanic sheeted dykes that form part of the ophiolitic mélange belt. These rocks show varying degrees of shearing due to the Fatira Shear Zone, which mainly consists of protomylonite, mylonite, and ultramylonite. The area is included in the Barud Gneissic Complex, along the ENE-trending dextral shear zone of the Qena-Safaga Line. The protolith underwent crustal shortening, leading to dextral movement along the Fatira Shear Zone. A study utilizing Landsat-8 imagery and the SAM method applied to ASTER data identified iron oxides, along with zones of chlorite and CO3-OH-bearing minerals, in the study area. The SAM algorithm mapped the distribution of common iron minerals, showing moderate to high lineament density and metavolcanic composition. The BIFs appear as thick single bands (3-4 m) along the outer edges of the shear zone and as thinner multiple bands within its central part. Field observations and mineralogical analyses indicate that the single bands consist of martitized magnetite-silicate facies, suggesting they are relatively unaltered. In contrast, the multiple bands comprise magnetite-chert-jasper facies, indicating significant alteration. Geochemical analyses support a hydrothermal genesis for the BIFs, with shearing planes acting as pathways for fluid flow. It is inferred that the protoliths of the BIFs originate from the host sheared metavolcanic sheeted dykes, which were affected by hydrothermal solutions. This research highlights the importance of integrating fieldwork, remote sensing, and laboratory analyses to understand better the formation and distribution of BIFs in tectonically active regions. The findings shed light on hydrothermal-related BIF formation within the sheared metavolcanic setting of the Wadi Fatira area and provide a useful framework for understanding iron mineralization in similar tectonically controlled environments.