ARTICLE Granitoid-associated gold mineralization in Egypt: a case study from the Atalla mine Basem Zoheir 1,2 & Fatma Deshesh 3 & Curt Broman 4 & Iain Pitcairn 4 & Ahmed El-Metwally 3 & Shabaan Mashaal 3 Received: 30 April 2017 /Accepted: 23 October 2017 # Springer-Verlag GmbH Germany 2017 Abstract Gold-bearing sulfide-quartz veins cutting mainly through the Atalla monzogranite intrusion in the Eastern Desert of Egypt are controlled by subparallel NE-trending brit- tle shear zones. These veins are associated with pervasive sericite-altered, silicified, and ferruginated rocks. The hosting shear zones are presumed as high-order structures of the Najd- style faults in the Central Eastern Desert (~ 615–585 Ma). Ore minerals include an early pyrite-arsenopyrite (±pyrrhotite) min- eralization, partly replaced by a late pyrite-galena-sphalerite- chalcopyrite (±gold/electrum ± tetrahedrite ± hessite) assem- blage. Gold occurs as small inclusions in pyrite and arsenopy- rite, or more commonly as intergrowths with galena and sphalerite/tetrahedrite in microfractures. Arsenopyrite geothermometry suggests formation of the early Fe-As-sulfide mineralization at 380–340 °C, while conditions of deposition of the late base metal-gold assemblage are assumed to be below 300 °C. Rare hessite, electrum, and Bi-galena are associated with sphalerite and gold in the late assemblage. The early and late sulfide minerals show consistently a narrow range of δ 34 S ‰ (3.4–6.5) that overlaps with sulfur isotopic values in ophiolitic rocks. The Au-quartz veins are characterized by abundant CO 2 and H 2 O ± CO 2 ± NaCl inclusions, where three-dimensional clusters of inclusions show variable aqueous/carbonic propor- tions and broad range of total (bimodal) homogenization tem- peratures. Heterogeneous entrapment of immiscible fluids is interpreted to be caused by unmixing of an originally homog- enous, low salinity (~ 2 eq. mass % NaCl) aqueous-carbonic fluid, during transition from lithostatic to hydrostatic condi- tions. Gold deposition occurred generally under mesothermal conditions, i.e., 1.3 kbar and ~ 280 °C, and continued during system cooling to < 200 °C and pressure decrease to ~ 0.1 kbar. Based on the vein textures, sulfur isotope values, compo- sition of ore fluids, and conditions of ore formation, we sug- gest that the Atalla monzogranite intrusion acted only as a competent structural host for ore deposition from shear-relat- ed, metal-rich fluids migrated up from depth. This model is also presumed for most granitoid-associated Au deposits in the region, considering the similarity in their structural con- trol, alteration pattern and mineralogy, and chemistry of the ore fluids. Keywords Atalla gold deposit . Granitoid-associated Au . Structural control . Fluid inclusions . Sulfur isotopes Introduction The presence of more than a hundred gold mining sites dis- persed in the Eastern Desert (ED) of Egypt reflects significant mining activity in the region dating back to ancient times (e.g., Klemm and Klemm 2013). The area is considered to be highly prospective for undiscovered gold deposits that occur as shear zone-hosted, disseminated sulfide mineralization or as quartz- carbonate veins along major structures in ophiolitic and island Editorial handling: B. Lehmann * Basem Zoheir basem.zoheir@gmail.com 1 Department of Geology, Faculty of Science, Benha University, Benha 13518, Egypt 2 Institute of Geosciences, University of Kiel, Ludewig-Meyn Str. 10, 24118 Kiel, Germany 3 Department of Geology, Faculty of Science, Mansoura University, 35516, El-, Mansoura, Egypt 4 Department of Geological Sciences, Stockholm University, 10691 Stockholm, Sweden Miner Deposita https://doi.org/10.1007/s00126-017-0772-2