Egyptian Eastern Desert

The publication of the Eastern Desert Roads Surveys brings together the research of two survey projects, the Michigan-Assiut Koptos-Eastern Desert Project and the University of Delaware-Leiden University Eastern Desert Surveys. From 1987 to 2001 and intermittently thereafter until 2015, these two survey teams worked independently to explore and document the archaeological remains along the routes connecting the Nile Valley cities of Koptos (modern Qift) and Apollinopolis Magna (modern Edfu) to the Red Sea port city of Berenike in Egypt. The result of these surveys was the documentation of seventy discrete archaeological sites ranging in date from the late Dynastic to the Late Roman periods, with many sites demonstrating long-term, multi-period occupation. The survey also recorded road sections, route marking cairns and graves/cemeteries.

This monograph brings together and integrates the discoveries of both teams, presenting a coherent analysis of the extensive surveys and the materials documented by each. Emphasis is placed on the physical setting of each site, its material remains--including preserved architecture, pottery and other surface finds--and relevant textual evidence, such as inscriptions, ostraka and related historical texts. A single chapter in gazetteer form is devoted to the sites themselves (excluding mines and quarries, which form a separate chapter), while other chapters present the geology of the region and ancient mines and quarries, which made use of the road network, the pottery evidence by phase, and specialist studies. An Introductory chapter offers historical and disciplinary context for the surveys and their subjects, tying the Berenike-Nile roads surveys into the corpus of archaeological surveys in Egypt and the wider Mediterranean world.

The Neoproterozoic peridotite-chromitite complexes in the Central Eastern Desert of Egypt, being a part of the Arabian-Nubian Shield, are outcropped along the E–W trend from Wadi Sayfayn, Wadi Bardah, and Jabal Al-Faliq to Wadi Al-Barramiyah, from east to west. Their peridotites are completely serpentinized, and the abundance of bastite after orthopyroxene suggests harzburgite protoliths with subordinate dunites, confirmed by low contents of Al 2 O 3 , CaO and clinopyroxene (b 3 vol%) in bulk peridotites. The primary olivine is Fo89.3– Fo92.6, and the residual clinopyroxene (Cpx) in serpentinites contains, on average, 1.1 wt% Al 2 O 3 , 0.7 wt% Cr 2 O 3 , and 0.2 wt% Na 2 O, similar in chemistry to that in Izu-Bonin-Marian forearc peridotites. The wide range of spinel Cr-number [Cr/(Cr + Al)], 0.41–0.80, with low TiO 2 (0.03 wt%), MnO (0. 3 wt%) and Y Fe [(Fe 3+ /(Cr + Al + Fe 3+) = 0.03 on average)] for the investigated harzburgites-dunites is similar to spinel compositions for arc-related peridotites. The partial melting degrees of Bardah and Sayfayn harzburgites range mainly from 20 to 25% and 25 to 30% melting, respectively; this is confirmed by whole-rock chemistry and Cpx HREE modelling (~20% melting). The Barramiyah peridotite protoliths are refractory residues after a wide range of partial melting, 25–40%, where more hydrous fluids are available from the subducting slab. The Neoproterozoic mantle heterogeneity is possibly ascribed mainly to the wide variations of partial melting degrees in small-scale areas, slab-derived inputs and primordial mantle compositions. The Sayfayn chromitites were possibly crystallized from island-arc basaltic melts, followed by crystallization of Barramiyah chromitites from boninitic melt in the late stage of subduction. The residual Cpx with a spoon-shape REE pattern is rich in both LREE and fluid-mobile elements (e.g., Pb, B, Li, Ba, Sr), but poor in HFSE (e.g., Ta, Nb, Zr, Th), similar to Cpx in supra-subduction zone (SSZ) settings, where slab-fluid metasomatism is a prevalent agent. The studied chromitites and their host peri-dotites represent a fragment of sub-arc mantle, and originated in an arc-related setting. The systematic increase in the volume of chromitite pods with the increasing of their host-peridotite thickness from Northern to Southern Eastern Desert suggests that the thickness of wall rocks is one factor controlling the chromitite size. The factors controlling the size of Neoproterozoic chromitite pods are the thickness, beside the composition, of the host re-fractory peridotites, compositions and volumes of the supplied magmas, the amount of slab-derived fluids, and possibly the partial melting degree of the host peridotites.

The archaeological seasons conducted in Wadi Sikait in 2020 and 2021 have increased our knowledge of the emerald mining in Roman Egypt, but also of the mining communities that lived in extensive settlements such as Sikait. This paper focuses on these aspects by presenting the archaeological work done in constructive complexes and religious edifices at this site and the intensive survey of the surrounding emerald mining areas; a work that has allowed a breakthrough regarding our understanding of the emerald extraction and commercialization in the Graeco-Roman and Byzantine periods.

This paper details the mode of occurrence, petrography, and chemistry of mineral inclusions hosted in chromian spinels of the Neoproterozoic chromitites in the Southern Eastern Desert of Egypt. Neoproterozoic podiform chromitites from the Arais, Balamhindit, and Abu Dahr areas, in the Southern Eastern Desert, can be texturally and chemically classified into two main types: primary high-Al (spinel Cr# b 0.67) and high-Cr (spinel Cr# N 0.75) chromitites. The former, being free of primary-mineral inclusions, was crystallized mainly from the MORB-like tholeiitic melt generated during proto-forearc spreading at the initiation of subduction, whereas the latter was formed from boninitic melts resulting from the high-degree melting of the sub-arc depleted mantle in the presence of slab-derived fluids at a mature-arc stage. The primary mineral inclusions, such as Na-and K-phlogopites, pargasite–edenite and olivine with subordinate pyroxenes, millerite, and laurite, were trapped within the chromian spinel during the magmatic precipitation of the chromitites. The Abu Dahr chromitites are free of primary hydrous inclusions; on the other hand, Arais and Balamhindit high-Cr chromitites are enriched in Na-and K-phlogopites, respectively, as a result of a difference in the K/Na ratio of the magma responsible for chromitite crystallization at different mantle depths. This difference in the K/Na ratio can possibly be attributed to fractionation of the upward-migrating hydrous fluids/melts by the crystallization of K-or Na-rich minerals. The Balamhindit complex, where the chromitite showed K-phlogopite inclusions within the chromian spinel, was probably derived from a deeper part of the mantle than the other areas, where the chromitite shows inclusions of Na-rich hydrous phases. Both K-and Na-phlogopites were possibly formed from alkali-rich hydrous fluids/melts trapped within the chromian spinels during the chromitite formation at different mantle depths, where the K/Na ratio decreases upward through the incorporation of Na from the peridotite wall-rock, combined with the precipitation of K-rich phases at deeper depths. The chemistry of both primary mineral inclusions and chromian spinels suggests an arc-related tectonic setting for our chromitites that were crystallized at 1000 °C–1300 °C under pressures b3 GPa. The host peridotites were generated during the proto-forearc extension and emplaced as a result of the collision of the intra-oceanic arc with the Bitan gneiss. The chromitite parental magmas are rich in K, Na, LREE, B, Cs, Pb, Sr, Li, Rb and U relative to HREE and HFSE (Nb, Ta, Th), reflecting the alkalic fluids/melts that prevailed during the chromitite genesis.

The studied sulfide mineralizations of Atshan and Darhib areas are related to the south Eastern Desert shear zones. They are hosted in talc-and tremolite-talc-rich rocks and also in meta-basaltic dykes and quartz-veins. The principal mineralization in Atshan includes sphalerite, pyrite, chalcopyrite, galena and pyrrhotite, whereas that in Darhib comprises chalcopyrite, sphalerite, pyrite, and galena with subordinate bornite and covellite. Darhib mineralization contains traces of altaite and electrum. Altaite has the highest Te concentrations suggesting crystallization under low fS 2 and/or high fTe 2 conditions, probably due to S budget consumption from the hydrothermal fluids in the late stage of deposition. Electrum has the highest Au contents with gold fineness value falling within the range of epithermal Au-Ag deposits. The dominance of recrystallized and replacement textures in the studied mineralizations suggests a secondary or post-depositional metamorphic overprint. The significant Cd contents in sphalerite from remobilized massive mineralizations hosted in tremolite-talc-rich rocks indicate crystallization at ~250-300 °C. Galena hosted in tremolite-talc-rich rocks is characterized by exceptionally high selenium and tellurium contents, indicating its generation from relatively Se-Te-enriched hydrothermal fluids. Pyrrhotite hosted in quartz-veins from Atshan was formed under lower sulfur activity (aS 2) and oxygen fugacity (fO 2). Covellite and bornite were formed due to chalcopyrite oxidation, revealing a role of supergene process. Shear zones, possibly produced during later thrust faulting, were acted as channel ways for hydrothermal mineralizing fluids that may have modified and/or precipitated the mineralization. Mineralizing fluids have probably resulted from dehydration during metamorphism and/or late-magmatic fluids from nearby granitic intrusions.