Geological and Mineralogical Analysis of Phosphorites in the Jebel Dhyr Syncline, Eastern Algerian Atlas

Abstract

Abstract The characterization of phosphorite features within specific North African sedimentary series remains incomplete. Hence, the primary aim of this research is to determine the composition of powder patterns and phosphatic allochem fragments within the Jebel Dhyr syncline, situated in northeastern Algeria. By focusing on this region, the study endeavors to investigate the mineralogical properties and geochemical aspects of Paleocene-Eocene phosphorites in the broader context of North Africa. The methodology employed encompasses geological, petrographic, geochemical, and mineralogical analyses of the rocks. To achieve this objective, we have employed various techniques including thin section analysis, atomic absorption spectrometry, and X-ray diffraction (XRD). The geological section across the Jebel Dhyr area has revealed a succession of horizontally layered rocks. These rocks consist of eight prominent phosphorite layers interspersed with carbonate formations. Additionally, occasional thin layers of flint can be observed within these carbonate layers. XRD analysis of the whole rock established the presence of apatite group minerals such as hydroxylapatite, fluroapatite, francolite, and dahllite. Other minerals identified include carbonates, quartz, zeolites, feldspar, clays, sulphides, and gypsum. XRD recordings on the phosphatic allochem grains (pellets, coprolites, intraclasts, and shark teeth) identified different mineral phases, with coprolites and pellets showing hydroxylapatite and fluorapatite, sometimes associated with dahllite, while granules of different forms revealed hydroxylapatite associated with fluorapatite or francolite. Teeth from the Jebel Dhyr phosphate beam showed the systematic presence of fluorapatite. This study provides valuable information for the comprehensive utilization of phosphorus resources in the Algeria-Tunisia border.