Petrographical, Geochemical Characterstics and Evaluation of the 'Marblized' Ornamental Limestone of Wadi Abu Resha, Galala Plateau, Eastern Desert, Egypt

摘要

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.rnGeochemically, 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.rnThe petrographical, geochemical, physical-mechanical characteristics, in addition to the risk studies of the studied carbonates allow their economic exploitation.