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The auriferous quartz +/- carbonate veins at Dungash mine, central Eastern Desert of Egypt, are confined to similar to E-trending dilation zones within variably foliated/sheared metavolcanic/volcaniclastic rocks. The vein morphology and internal structures demonstrate formation concurrent with a dextral shear system. The latter is attributed to flexural displacement of folded, heterogeneous rock blocks through transpression increment, late in the Neoproterozoic deformation history of the area. Geochemistry of the host metavolcanic/metavolcaniclastic rocks from the mine area suggests derivation from a low-K, calc-alkaline magma in a subduction-related, volcanic arc setting. In addition, chemistry of disseminated Cr-spinels further constrain on the back-arc basin setting and low-grade metamorphism, typical of gold-hosting greenstone belts elsewhere.

Mineralogy of the mineralized veins includes an early assemblage of arsenopyrite-As-pyrite-gersdorffite +/- pyrrhotite, a transitional pyrite-Sb-arsenopyrite +/- gersdorffite assemblage, and a late tetrahedritechalcopyrite-sphalerite-galena-gold assemblage. Based on arsenopyrite and chlorite geothermometers, formation of gold-sulfide mineralization occurred between similar to 365 and 280 degrees C. LA-ICP-MS measurements indicate the presence of refractory Au in arsenian pyrite (up to 53 ppm) and Sb-bearing arsenopyrite (up to 974 ppm). Abundant free-milling gold associated with the late sulfide assemblage may have been mobilized and re-distributed by circulating, lower temperature ore fluids in the waning stages of the hydrothermal system.

Based on the isotopic values of vein quartz and carbonate, the calculated average delta(OH2O)-O-18 values of the ore fluids are 5.0 +/- 1.4 parts per thousand SMOW for quartz, and 3.3 +/- 1.4 parts per thousand for vein carbonate. The measured carbonate delta C-13 values correspond to ore fluids with delta C-13(co2) = -6.7 +/- 0.7 parts per thousand PDB. These results suggest a mainly metamorphic source for ore fluids, in good agreement with the vein morphology, textures and hydrothermal alteration. The calculated delta S-34(H25) values for early, transitional, and late sulfide assemblages define three distinct ranges (similar to 1.5-3.6 parts per thousand), (similar to 0.4-1.0 parts per thousand), and (-3.7 parts per thousand to -1.9 parts per thousand), respectively. The systematic evolution towards lighter delta S-34 values may be attributed to recrystallization, or to ore fluid buffering under variable physicochemical conditions.

The shear zone-related setting, mineralogy and isotopic characteristics of gold mineralization in Dungash mine are comparable with other orogenic gold deposits in the region (e.g., Barramiya deposit), which may suggest a regional setting controlling gold metallogeny of the region. This setting should guide future exploration programs in the central Eastern Desert province. (C) 2013 Elsevier Ltd. All rights reserved.