Composition of black shale from Quseir, Red sea, Egypt with emphasis on the sequential extraction of some metals

The black shales Duwi Formation, within Gabel El-Atshan in Quseir area are rich in sonic trace elements. Petrogaphically, the studied shales are dark colored mudstone enriched in phosphatic elastics and are highly fossiliferous. The presence of framboidal pyrite revealed that the studied black shales were deposited under reducing conditions. Mineralogically, XRD revealed that the studied samples consist of smectite, kaolinite, mixed layer [smectite/illite], illite in addition to minor chlorite. Such heterogeneous composition indicates recycling from pre-exiting clay sediments. The studied shales are relatively enriched in some heavy metals such as zinc and nickel. The SEM and EDX studies indicate that these metals are concentrated in the clayey materials but do not form minerals of their own. The present work provides new data on the speciation of such enriched metals. The sequential extraction proves that the heavy metals are largely bound to the residual phase [57% Zn, 51% Fe, 50% Cu. 18% Ni and 10% Mn]. However, the metals; Ni, Cu and Zn have mostly been extracted into the first three fractions

Petrographical, geochemical characterstics and evaluation of the [marblized] ornamental limestone of wadi Abu Resha, Galala plateau, Eastern desert, Egypt

The middle Eocene carbonate sediments of Wadi Abu Resha were deposited under inner to middle shelf, clear, open shallow marine environment. The ornamental limestones were affected by the heat that accompanied the compressional stress along the fault planes which controlled the area during the Oligocene and Neogene. However, the translucent alabaster of the studied area was formed by chemical precipitation and recrystallization [diagenetical processes] by the action of uprising hot water and during intensive weathering [karstification] and circulation of groundwater associated with the Oligocene volcanic eruption. Diagenesis occurred under submarine [micritic envelope, rim cement, micritization, micritic cement and compaction] and subaerial [extensive cementation, neomorphism and dissolution] environments. Mineralogically, the carbonates of Wadi Abu Resha are mainly composed of calcite. Geochemically, the studied carbonates have very low content of major elements other than CaO. Trace and rare earth elements are minor. The depletion in Sr content of the studied ornamental limestones may be attributed to the extensive diagenesis processes that affected these rocks. The concentration of Co, Cr, Mo and Pb is under the maximum permissible limits; consequently, no endemic diseases might occur in case the rock is used for domestic purpose. The petrographical, geochemical, physical-mechanical characteristics, in addition to the risk studies of the studied carbonates allow their economic exploitation

Diagenesis and geochemistry of the reefal facies of the Shagra formation, Ras Benas, Red sea coast, Egypt

Reefal sediments of the Shagra formation [Pliocene-Pleistocene] were developed under tectonic instability of the Ras Benas coastal region. This tectonic mobility, besides global sea level changes and climate variations, are most probably responsible for the vertical variation in microfacies, chemical composition, development and diagenetic modification of the reefal carbonates. Dolomite associated with gypsum within the reefal limestone indicates evaporation conditions during subaerial exposure. SEM examination shows dolomite rhombs up to 20 micro m and halite crystals range from 30 to 50 micro m. The X-ray diffraction analysis indicates that calcite, dolomite, gypsum and halite are the main mineral constituents, in a decreasing order of relative abundance. Geochemically, the Sr/Ca ratio points to the deposition of these reefal sediments under a shallow marine environment. The depletion in Na and Sr content indicates that the carbonate rocks of the studied area have been subjected to progressive diagenesis and dolomitization under less saline environment than sea water. Dolomitization processes took place by evaporation within the basal part of the Shagra Formation. The microfacies of the studied surface section of the Shagra Formation correlates with the published subsurface sedimentary section of the same formation and other surface sections along the Red Sea coast

Suggested mortars for restoration and conservation of some limestone historical structures

Conserving of weathered limestone historical structures is an important target for many interested Egyptian builders. Studying the original mortar of any limestone archeological building led to thinking about a new suitable mix design of mortar. The chemical composition of the old studied mortar shows enrichment in chlorides, ammonia and sulfates. Seven mixes composed of different quotients of sand, lime and gypsum were prepared for choosing the suitable one as restoring mortar. X-ray diffractograms of the suggested mortar mixes show composition of quartz, gypsum and calcium hydroxide as the main minerals comprising all mixes. Calcium silicate hydrate [C SH] and di- calcium silicate hydrate [CSH] phases were detected with mixes, which contain considerable gypsum and sand. Mix No.1 [60% sand, 30% lime and 10% gypsum] is considered to be the best blend for mortar. Such mix achieved reasonable compressive strength, bulk density and water absorption values along all of the studied curing times. This work suggests that the using of sand, lime and gypsum mortars is adequate for repairing and conserving the historical and archeological limestone buildings