Geology and genesis of EI-Dob tungsten ore deposit (North Eastern Desert, Egypt): Insights from fieldwork, petrography and remote sensing

EI-Dob ore deposit is one of twelve tin-tungsten mineral occurrences located in the Egyptian basement complex. Detailed fieldwork, petrography and remote sensing investigations were performed to map the area and to shed light on the genesis of the tungsten mineralization. The area is covered by syn-orogenic granodiorite, intruded by gabbro and late- to post-orogenic monzogranite and alkali-feldspar granite. The mineralization occurs as wolframite-bearing quartz veins, associated with greisen alteration zones, cutting through the granodiorite and monzogranite. The wolframite occurs as large, prismatic cm-size crystals, which are often concentrated and radially oriented in large nodules with up to 20 cm radius. Various image enhancement techniques, such as band combinations, band ratios, principle component analysis and minimum noise fraction, have been applied on ASTER and ETM+ datasets to perform detailed lithological and hydrothermal alteration mapping on the area. The mineralization is hosted by two alteration zones, which are spatially associated with the alkali-feldspar granite. Likely, during the post-orogenic extensions and magmatism, a magmatic-hydrothermal fluid was released, along with the incompatible tungsten, from the differentiating granitic melt phase. Intense interaction between this fluid and the surrounding granodiorite and monzogranite developed the greisen hydrothermal alteration zones and facilitated fluid cooling and the W mineralization.