Detailed documentation for the mineralized quartz veins and the wall-rock alteration zones at the Abu Khalag region reveals that the mineralizationoccurs along narrow discontinuous shear zones, and mostly hosted by green-schist assemblages. Shearing processes and retrograde metamorphism are one of the causes of remobilizing the auriferous quartz veins and re-deposit them at the appropriate physiochemical traps. The spatial array of Abu Khalag auriferous reefs, the zonal nature of the associated wall-rock alteration, and the structural/lithological evidences suggest that the mineralization is related to developed fluid flux during deformation/metamorphism. Gold nuggets morphology is sub to euhedral, and uneven grains, tabular and plated textures are common. Their color in all the placers is dull yellow to reddish brown and greenish yellow, reflecting (Fe, Cu) existence. Their surface is mainly medium to moderately coarse-grained. The euhedral nuggets reflect insitu formation at high temperatures with possible role of bacteria. No dendritic patterns for gold were observed. Abu Khalaggold-bearing quartz veins are associated with disseminated pyrite, arsenopyrite, chalcopyrite, pyrrhotite, galena, and iron ores. The deposition of gold was contemporaneous to retrogressive metamorphism and the rejuvenation along the shear zones during D2. The auriferous quartz reefs are variable in colour, size, and are preferably hosted in the metasediments, especiallyamphibolites and calc-silicate rather than quartzites and gneisses, suggesting that gold mineralization is also lithologically controlled. The primary occurrence of gold grains is free-lodes in silicates and/or inside the disseminated sulphides in the quartz reefs. The Au-quartz veins showing two main groups/ phases. Phase one is concordant with schistosity of the bedrocks, showing sacaroidal textures, banded structures, and usually occur as discontinuous isolated patches (pinch and swell). The size of these veins ranging from few centimetres (stringer, veinlet) to more than half a metre. The Au-grade in this group ranging between 0.05 and 1.9 ppm. The second phase of quartz veins is massive formed by ductile dextral shearing, and is in the tension gashes. The concentrations of gold in this type ranging (0.05-0.4) ppm, and have average 1 metre thickness. The geochemical, lithological, structural, and mineralogical features with the style of wall rock alterations of the Au-bearing quartz veins suggest that they belong to mesothermal (orogenic) gold type.Gold also found as placer deposits, which covered vast parts of the study area. Associated gangue minerals with gold in the stream sediments are quartz, calcite, sericite, siderite, ankerite, dolomite, K-feldspars, zircon, rutile, tourmaline, epidote, and graphite. Gold nuggets shapes and sizes reflect that quartz reefs are not the only mineralized source in the study area. The gold background value in the fine-fractions of stream sediments is 0.21 ppb, the threshold is 2.91 ppb, and the anomalous value is 3.0 ppb. Cu and Zn are the main pathfinder elements for gold based on stream sediments geochemistry.
