title: Raman investigations of Upper Cretaceous phosphorite and black shale from Safaga District, Red Sea, Egypt.
abstract: The mineral composition of the Upper Cretaceous Duwi phosphorite deposits and underlying Quseir Variegated Shale from Safaga district, Red Sea Range, Egypt, was investigated by dispersive and Fourier transformed Raman spectroscopy. The only phosphorous containing mineral detected in the phosphorite deposits was carbonate fluorapatite. Often carbonate fluorapatite appears associated with calcium sulfate and seldom with calcium carbonate in the investigated samples. Iron is present in the form of goethite and pyrite in the phosphorite layer, while pyrite, marcasite and hematite were identified in the Quseir Shale samples. Also, a high amount of disordered carbon was detected in the black shale layers. The Raman results confirm the hypothesis that the formation of the phosphorites took place in a marine environment. During the formation of black shale, the redox conditions changed, with the pH reaching values of 4 or even lower. Diagenetic and weathering transformations had taken place in the phosphorite deposits, calcium sulfate and goethite being products of these types of processes.
authors.affiliation: Institute of Physical Chemistry, Friedrich Schiller University Jena, Germany.
authors.forename: Valerian
authors.initials: V
authors.lastname: Ciobotă
authors.forename: Walid
authors.initials: W
authors.lastname: Salama
authors.forename: Paul
authors.initials: P
authors.lastname: Vargas Jentzsch
authors.forename: Nicolae
authors.initials: N
authors.lastname: Tarcea
authors.forename: Petra
authors.initials: P
authors.lastname: Rösch
authors.forename: Ahmed
authors.initials: A
authors.lastname: El Kammar
authors.forename: Rania S
authors.initials: RS
authors.lastname: Morsy
authors.forename: Jürgen
authors.initials: J
authors.lastname: Popp
mesh_terms: D001031:Apatites / Q000737:chemistry; D004534:Egypt; D019015:Geologic Sediments / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D008903:Minerals / Q000737:chemistry*; D009792:Oceans and Seas; D010710:Phosphates / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013997:Time Factors
chemical_list: D001031:Apatites; D008903:Minerals; D010710:Phosphates; C090013:phosphorite; D007501:Iron
keywords: Apatite; Phosphorite minerals; Raman spectroscopy