Gold-bearing volcanogenic massive sulfides and orogenic-gold deposits in the Nubian Shield

Abstract

The Nubian Shield is a large region of juvenile Neoproterozoic rocks that, together with its counterpart in the Arabian Shield, is part of a major accretionary orogen. It originated as late Tonian-Cryogenian island arcs on the site of the Mozambique Ocean formed by breakup of Rodinia. Arc collisions, subsequent magmatism, volcanism, sedimentation, and orogeny, associated with Cryogenian-Ediacaran convergence of cratonic blocks during the assembly of Gondwana, converted the region into the East African Orogen. The Nubian Shield region also has important Paleozoic-Neogene strata, including significant flood basalt, that conceal large areas of the basement. The Shield contains hundreds of gold occurrences and evidence of a 5,500-year history of gold mining. The main deposit types are orogenic gold and gold associated with volcanogenic massive sulfides (VMS). The juvenile subduction-related origin of the Shield rocks and the pervasiveness of shearing and greenschist-to-amphibolite facies metamorphism associated with late Neoproterozoic orogeny are geologic features highly favorable for the development of these types of deposits, and make the combined Arabian-Nubian Shield the Earth's largest Neoproterozoic gold resource. Gold-bearing VMS deposits are currently mined at Bisha (Eritrea) and are soon to be

Intrusion‐related Gold Deposits in Egypt

“…Auriferous exhalative deposits were formed concomitant with the arc volcanicity at ~750 Ma as a result of interaction between volcanically derived fluids (hot brines) and sea water (Botros, 1995(Botros, , 2003. These deposits include the auriferous Algoma-type BIF, where gold occurs in these deposits either restricted stratigraphically (strata-bound) within the BIF or is concentrated in quartz veins adjacent to or within the BIF (Botros, 1991(Botros, , 1995El Shimi, 1998;El Shimi and Soliman, 2002;Botros, 2021), as well as disseminated in the auriferous tuffaceous metasedimentary rocks (Botros, 1993) and gold-bearing VMSDs in the Um Samiuki and Hamama districts (Searle et al, 1976;Botros, 2003;Johnson et al, 2017;Bampton, 2017). The suggested age for these exhalites in the Eastern Desert is compatible with the age suggested for the genesis of the BIF in the Eastern Desert (Ali et al, 2009;Stern et al, 2013;Stern, 2018;Stern and Ali, 2020) and the ages suggested for other VMSDs in the ANS such as Jabal Sayid, Shayban and Baydan (~745Ma); Shiab Lamisah and As Safra (750Ma) (Volesky et al, 2017 and references therein).…”

Ore-forming mechanism and its relationship with deformational and metamorphic episodes at Haimur gold mine, Nubian Shield, Egypt

“…Haimur gold deposit (Figs 1, 2) (south Eastern Desert of Egypt) resembles a representative model for the vein-style gold deposits in Egypt (e.g. Sukari (Johnson et al 2017), Hamash (Johnson et al 2017), Fawakhir (Zoheir et al 2015)). It hosts economic concentrations of Au and other sulphide minerals (the gold contents lie Meert & Lieberman (2008) in which the Neoproterozoic Arabian-Nubian Shield (ANS) represents the northern part of the East African Orogen (EAO).…”

Tectonic record and gold mineralization in the central part of the Neoproterozoic Keraf suture, Gabgaba district, NE Sudan

“…The Arabian-Nubian shield (ANS; Fig. 1a, b) constitutes the main Neoproterozoic gold province worldwide (Johnson et al, 2017). ANS deposits are mostly classified as orogenic gold occurrences preferentially hosted by major shear zones (e.g., Elsamani et al, 2001;Botros, 2002Botros, , 2004Helmy et al, 2004;El Kazzaz, 2012;Osman, 2014;Helmy and Zoheir, 2015;Khalil et al, 2016;Fawzy, 2017;Zoheir et al, 2019aZoheir et al, , 2019bZoheir et al, , 2019c, including the Keraf shear zone (KSZ) (Johnson et al, 2017).…”

“…1a, b) constitutes the main Neoproterozoic gold province worldwide (Johnson et al, 2017). ANS deposits are mostly classified as orogenic gold occurrences preferentially hosted by major shear zones (e.g., Elsamani et al, 2001;Botros, 2002Botros, , 2004Helmy et al, 2004;El Kazzaz, 2012;Osman, 2014;Helmy and Zoheir, 2015;Khalil et al, 2016;Fawzy, 2017;Zoheir et al, 2019aZoheir et al, , 2019bZoheir et al, , 2019c, including the Keraf shear zone (KSZ) (Johnson et al, 2017). The KSZ is mapped in northeastern Sudan and southeastern Egypt, and overprints the ~500 km-long, ~70 kmwide, north-striking ophiolite-decorated Keraf suture (KS) which is rooted deep into the lithosphere (Almond and Ahmed, 1987;Abdelrahman, 1993;Abdelsalam et al, 1995;Abdelsalam and Stern, 1996a;Ahmed Suliman, 2000).…”