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<p>The Egyptian Nubian Shield (ENS) represents the northeastern extension of the East African Orogenic Belt. The East African Orogeny (EAO) emerged as a result of the closure of the Mozambique Ocean, which served as a demarcation line between the East and West Gondwana continental masses. This tectonic phenomenon led to the consolidation of various juvenile arc and back-arc igneous and sedimentary rock formations, dating from approximately 870 to 625 Ma. The resulting terrane sutures are often characterized by mafic–ultramafic ophiolitic assemblages and remnants. The ENS exhibits three predominant structural domains: the southern compressional domain (SCD), the central transpressional domain (CTD), and the northern extensional domain (NED). The central transpressional domain contains the most significant gold mines and occurrences in the ENS. Gold extraction in Egypt has a long history, facilitated by the Egyptian Geologic Survey and Mining Authorities. The formation of orogenic gold in the Eastern Desert is attributed to the processes following the accretion of arc terranes in the ENS, a period marked by significant geodynamic changes. The post-accretion phase witnessed the emergence of regional transpressional shear zones, which notably influenced the distribution of gold-bearing quartz and quartz–carbonate veins throughout the Eastern Desert. A genetic relationship exists between gold mineralization and the transpressional tectonics characteristic of the Najd Fault System in the central transpressional domain (CTD). In the southern compressional domain (SCD), gold mineralization is associated with late-stage brittle–ductile shear zones. The transpressional event, characterized by E–W shortening, occurred at ~620–580 Ma. The shear zones in the central ENS region exhibit brittle to brittle–ductile characteristics, predominantly oriented NW to N–NW. The origin of shear-related gold can be traced back to the accumulation of arc terranes in the ENS, evolving from a phase characterized by compressional and transpressional terrane accretion to one marked by transtensional shearing following the amalgamation. This era also marked a shift from pre-accretionary to syn-accretionary magmatism, leading to the formation of late or post-tectonic granites. The Najd Fault System acts as a pathway for mineralizing fluids, which move through shear planes oriented in NW–SE, N–S, and NE–SW directions. The gold-bearing quartz–carbonate veins in the Eastern Desert are categorized as shear-related gold deposits, with their formation conditions established around 600–590 Ma.</p>

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Shear-related gold mineralization in the Egyptian Nubian Shield, East African orogenic belt

  • 期刊论文

  • 发表日期：

    2025年5月12日

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  • Mohamed A. Abd El‑Wahed

摘要

The Egyptian Nubian Shield (ENS) represents the northeastern extension of the East African Orogenic Belt. The East African Orogeny (EAO) emerged as a result of the closure of the Mozambique Ocean, which served as a demarcation line between the East and West Gondwana continental masses. This tectonic phenomenon led to the consolidation of various juvenile arc and back-arc igneous and sedimentary rock formations, dating from approximately 870 to 625 Ma. The resulting terrane sutures are often characterized by mafic–ultramafic ophiolitic assemblages and remnants. The ENS exhibits three predominant structural domains: the southern compressional domain (SCD), the central transpressional domain (CTD), and the northern extensional domain (NED). The central transpressional domain contains the most significant gold mines and occurrences in the ENS. Gold extraction in Egypt has a long history, facilitated by the Egyptian Geologic Survey and Mining Authorities. The formation of orogenic gold in the Eastern Desert is attributed to the processes following the accretion of arc terranes in the ENS, a period marked by significant geodynamic changes. The post-accretion phase witnessed the emergence of regional transpressional shear zones, which notably influenced the distribution of gold-bearing quartz and quartz–carbonate veins throughout the Eastern Desert. A genetic relationship exists between gold mineralization and the transpressional tectonics characteristic of the Najd Fault System in the central transpressional domain (CTD). In the southern compressional domain (SCD), gold mineralization is associated with late-stage brittle–ductile shear zones. The transpressional event, characterized by E–W shortening, occurred at ~620–580 Ma. The shear zones in the central ENS region exhibit brittle to brittle–ductile characteristics, predominantly oriented NW to N–NW. The origin of shear-related gold can be traced back to the accumulation of arc terranes in the ENS, evolving from a phase characterized by compressional and transpressional terrane accretion to one marked by transtensional shearing following the amalgamation. This era also marked a shift from pre-accretionary to syn-accretionary magmatism, leading to the formation of late or post-tectonic granites. The Najd Fault System acts as a pathway for mineralizing fluids, which move through shear planes oriented in NW–SE, N–S, and NE–SW directions. The gold-bearing quartz–carbonate veins in the Eastern Desert are categorized as shear-related gold deposits, with their formation conditions established around 600–590 Ma.