Re-Os geochronology of gold mineralization in the Fawakhir area, Eastern Desert, Egypt

Abstract

We report the first Re-Os data on gold-associated arsenopyrite from mesothermal gold-quartz veins in the ancient Egyptian Fawakhir–El Sid gold mining district in the central Eastern Desert. This mining district has an ~5000-year-old history and is displayed in the Turin Papyrus Map (about 1150 BC), which is widely acclaimed as the world’s oldest geographic map, as well as the oldest geologic and mine map. The Fawakhir–El Sid district is part of a regional NNW-trending shear corridor (15 km wide) that hosts several other historic gold mines associated with left-lateral wrench structures and related granite intrusions. Vein-style gold mineralization is hosted within and at the margin of an I-type and magnetite-series monzogranite, the Fawakhir granite intrusion, and a Pan-African (~740 Ma) ophiolite sequence. The ore mineralogy of the mineralized quartz veins includes pyrite-arsenopyrite-pyrrhotite-sphalerite-galena-chalcopyrite-electrum plus a number of tellurides of Ag, Au, and Bi. The ¹⁸⁷Re/¹⁸⁸Os versus ¹⁸⁷Os/¹⁸⁸Os regression on 5 points of arsenopyrite gives an age of 601 ± 17 Ma with an initial ¹⁸⁷Os/¹⁸⁸Os of 0.24 ± 0.07 (2 σ; MSWD = 17). This age coincides within error with the U-Pb age on zircon from the Fawakhir monzogranite (598 ± 3 Ma). The age coincidence and the hydrothermal Te and Bi metal signature suggest a foremost role of granite-related fluids in the quartz-vein system.

Keywords:

• Re-Os dating
• gold mineralization
• Fawakhir area
• Wadi Hammamat
• Egypt

Notes

1. Andresen et al. (2009) describe their sample from the Fawakhir intrusion as ‘Fawakhir monzodiorite’. However, sample location and petrographic description assign this sample to the younger intrusive phase, i.e. the Fawakhir granite (personal communication with A. Andresen).