Fluid evolution in the El-Sid gold deposit, Eastern Desert, Egypt

Abstract

Auriferous quartz (+carbonate) veins in the El-Sid mine cut through the western margin of the Fawakhir granitic intrusion and the immediate country ophiolites. Gold mineralization is spatially and temporally associated with ENE-WSW fault/shear zones developed late in the deformational history of the area. Field and microscopic studies suggest two distinct ore stages; namely an early gold-Fe-As-sulphide, and a late gold-base metal mineralization. New microthermometric and Raman data suggest gold deposition as a result of a complex history of fluid immiscibly, dilution of low-salinity aqueous-carbonic fluids in the early mineralization stage, while wall-rock alteration and pressure loss precipitated Au from intermediate-salinity aqueous ore fluids during the late stage. Fluid inclusion isochoric reconstructions, combined with oxygen and sulphur isotope data, indicate conditions of 320 + 20 8C and 1.3 + 0.2 kbar for the early gold-Fe-As-sulphide mineralization, and c. 200 + 15 and 0.6 + 0.9 kbar for the late gold-Zn-Pb-Cu-sulphide stage. The clockwise evolution path in pressure-temperature space likely documents gold mineralization under post-peak metamorphic conditions. The calculated sulphide d 34 S H2S equilibrium values 29.04‰ to -4.75‰, may refer to a variable redox state of sulphur in the ore fluids from the early to late mineralization stages. The stable isotope signature of the vein quartz and calcite suggest mixed magmatic and metamorphic fluid sources (d 18 O H2O ¼ +4.9‰ to +7.4‰). Unusually low d 13 C values of calcite in the late mineralization (213.9‰ to 214.7‰) may reflect input of magmatic CO 2 and/or oxidized carbonaceous material in the infiltrating fluid.

Gold-transporting hydrothermal fluids in the Earth's crust: an introduction

“…These features were described also in previous studies of this deposit (e.g. Harraz 2000) and are interpreted by Zoheir & Moritz (2014) as a product of a magmatic fluid input into the Au vein network.…”

“…The Precambrian El-Sid orogenic gold deposit from Eastern Egypt is discussed by Zoheir & Moritz (2014). This is one of the most important gold deposits of Egypt, whose exploitation history dates back to the pharaonic time.…”

“…This is one of the most important gold deposits of Egypt, whose exploitation history dates back to the pharaonic time. Zoheir & Moritz (2014) provide a summary of the most recent geological and structural data on this deposit, which is made by sets of crack-seal and massive quartzcarbonate-pyrite-arsenopyrite-galena-sphalerite veins crosscutting a monzonite intrusion and an ophiolitic melange. These data are coupled with a dataset made of fluid inclusion microthermometry, Raman spectroscopy, oxygen and carbon isotope compositions of calcite and quartz, and arsenopyrite composition to provide a genetic model of the deposit.…”

Metal and fluid sources in a potential world-class gold deposit: El-Sid mine, Egypt

“…On the other hand, Pb and Re-Os isotopes data are used to infer the metal source(s) in many cases (e.g., Mathur et al 2000; Barra et al 2003). Several authors have attributed the source of fluid and heat in many gold deposits in the Eastern Desert of Egypt to regional-scale granitic intrusions and have identified associated ophiolitic rocks as the sources of metals (e.g., Takla et al 1990;Sharara 1999;El-Tokhi and El-Muslem 2002;Helmy et al 2004;Zoheir 2012;Zoheir and Moritz 2014). Sulfur isotope data of goldassociated ore minerals, i.e., arsenopyrite, pyrite, galena, sphalerite and chalcopyrite, suggest an igneous source of sulfur (Zoheir and Moritz 2014).…”

“…Several authors have attributed the source of fluid and heat in many gold deposits in the Eastern Desert of Egypt to regional-scale granitic intrusions and have identified associated ophiolitic rocks as the sources of metals (e.g., Takla et al 1990;Sharara 1999;El-Tokhi and El-Muslem 2002;Helmy et al 2004;Zoheir 2012;Zoheir and Moritz 2014). Sulfur isotope data of goldassociated ore minerals, i.e., arsenopyrite, pyrite, galena, sphalerite and chalcopyrite, suggest an igneous source of sulfur (Zoheir and Moritz 2014). Specific magmatic events thought to have introduced the ore-forming fluids are the syn-tectonic, subduction-related event that produced the older calc-alkaline granites (e.g., El-Gaby et al 1988) and the post-tectonic event that produced the younger alkaline to per-alkaline granites (e.g., Sabet et al 1976;Hussein 1990).…”