Mineralogy and ground gamma-ray spectrometric investigation for phosphates of Gabal Abu Had area, Central Eastern Desert, Egypt

Abstract

ABSTRACT The present study deals with geologic and mineralogic studies as well as gamma-ray spectrometric survey for uranium potential phosphates of Duwi Formation and environmental assessment at Gabal Abu Had environ. These phosphate deposits are considered as an important potential resource for uranium and rare earth elements as by-products. The study area lies to the NE of Qena town and dissected by Qena – Safaga asphaltic road. The Duwi Formation in the study area conformably overlies Qusseir Formation and underlies Dakhla Formation; this succession is capped with Esna and Thebes Formations and eroded along wadis which are filled with Quaternary deposits. Phosphate deposits (Duwi Formation) of Abu Had area are enriched with uranium, which may be extracted as a by-product of making fertilisers. Petrographic studies indicate that phosphate beds are composed of phosphatic particles which include collophane grains, bioclasts (bone and teeth fragments), as well as, non-phosphatic particles which include quartz, calcite and pyrite embedded in silica, calcite or iron oxides cement. XRD results showed that hydroxylapatite is the principal phosphate mineral, and the non-phosphate minerals include calcite, quartz, gypsum and anhydrite. Ground gamma-ray spectrometric results indicated that the study area has K values range from 0.2% to 4.4%, eTh values range from 0.5 to 18 ppm and eU values range from 0.5 to 100 ppm. The phosphate-bearing beds of Duwi Formation have the highest values of eU reach up to 100 ppm. The uranium anomalies mostly elongated in NW-SE trend that related to the NW-SE strike-slip faults of the area. The average value of annual effective dose rates of phosphates at Abu Had area equals 0.32 mSv/y which, less than the worldwide permissible level of annual effective dose rate (1 mSv/y).