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The Barramiya mine area is a tract of deformed Neoproterozoic ophiolitic melange sequences comprising metamorphosed volcano-sedimentary-serpentinite rocks in the central Eastern Desert of Egypt. The gold mineralization comprises a number of narrow anastomosing lodes of massive and brecciated gold+sulphide-quartz and quartz-carbonate veins. These veins are hosted by, or directly associated with highly deformed carbonaceous serpentinite and volcaniclastic schists along east-trending shear zones, commonly exhibiting pinch-and-swell and boudinage structures. Hydrothermal alteration is pervasive throughout the shear zones, with a common assemblage of chlorite, ankerite, sericite, +/-calcite, +/-magnetite, +/-graphite. Gold/electrum inclusions are common in pyrite coexisting with arsenopyrite and pyrrhotite, mostly where chlorite and carbonate are abundant, whereas free-milling gold appears as tiny grains along micro-fractures in the vein quartz or disseminated in the adjacent wallrocks. Inclusions of C-O-H fluids, mainly mono-phase carbonic (CO(2)+/-CH(4)+/-H(2)O) and two/three-phase aqueous-carbonic (H(2)O-NaCl-CO(2)+/-CH(4)) inclusions along intragranular trails and aqueous (H(2)O-NaCl+/-CO(2)) inclusions along transgranular trails are common in the auriferous quartz veins. The aqueous-carbonic inclusions were most likely entrapped during gold deposition and represent the ore fluid. Estimated pressure-temperature conditions for ore deposition based on arsenopyrite thermometry and using the isochores for aqueous-carbonic inclusions range from 1.2 to 2.5 kbar at 309-377 degrees C, consistent with brittle-ductile transition. Gold deposition from a dilute aqueous-carbonic ore fluid with significant concentrations of CH(4) added via interaction with the carbonaceous wallrocks may have been triggered by a sharp decrease in fO(2), caused by the CH(4) enrichment of the fluid and precipitation of carbonate.