Microbial control on the mineralogy of Arief El Naqa phosphates, Egypt

SEM examination of the pelletal phosphates from the Upper Cretaceous of Arief El Naqa in eastern Sinai reveals the presence of bacterial relics and globular clusters of phosphate, iron oxyhydroxides and halite. All have been identified only within cavities and in the phosphatic cement around phosphate particles. These microbial structures were, therefore, produced by the aid of microorganisms in association with infiltrating meteoric water from the nearby vegetation cover. They were able to accelerate the dissolution of pyrite and the leaching of phosphate particles to use phosphorus as a desired nutrient. Phosphate globular clusters and goethite framboids were formed as the result of crystal growth of the biologically precipitated precursor phases. Bacteria were simply available nucleation sites for binding of these nanoparticles. Halite clusters were also identified in a similar setting and show a co-genetic relationship with other types of microstructures. Therefore, the role of microorganisms in the f...