Genetically related Mo–Bi–Ag and U–F mineralization in A-type granite, Gabal Gattar, Eastern Desert, Egypt

Abstract Molybdenum–bismuth–silver and uranium–fluorine mineralization in the Gabal Gattar area are genetically related. Both are hosted in fractionated and hydrothermally altered A-type granite. While Mo–Bi–Ag ore is hosted in NS striking quartz veins, the U–F mineralization forms batches and micro-veinlets, controlled by NNE to NW trending structures. U was incorporated in late-magmatic hypogene minerals (e.g. zircon and xenotime) and in U–Th-minerals closely associated with fluorite. Molybdenite, native bismuth, galena, chalcopyrite, sphalerite, aikinite “PbCuBiS 3 ”, berryite “S 16 (Cu,Ag) 6 Bi 7 Pb 3 ” and native silver were identified in the quartz veins. Fluid inclusions occur in fluorite (Type-1) associated with U minerals and in quartz (Type-2) from Mo-bearing veins. Type-1 and 2 inclusions homogenize at temperatures between 220 °C and 106 °C, their salinity ranges from 1.3 to 10 wt.% NaCleq, respectively. F-rich fluids accumulated at the last stage of granite crystallization, extracted ore metals and deposited them in a shallow hydrothermal system. Mo, Bi and Ag precipitated earlier from saline fluids due to cooling, fluid mixing and wallrock sulfidation. U–F minerals precipitated from low-salinity fluids after high input of meteoric water.