Abstract
X-Ray diffraction results for the study mine are mainly represented by two phases (phosphatic and non-phosphatic). First phase is represented by apatite (fluorapatite) which is the dominant. The second phase includes carbonate minerals; calcite, dolomite, evaporated mineral (gypsum), sulphide mineral (pyrite), in addition to quartz as a silicate mineral. These results are confirmed by the petrographic study. The detailed microscopic examinations indicate that the phosphorites at the study mine is essentially composed of phosphatic lithoclasts (mainly collophane), phosphatic bioclasts (bone fragments, spines and teeth of vertebrates such as shark fish as well as coprolites), opaques, and quartz embedded in a microcrystalline phosphatic matrix (contains some of dahllite) associated with a microcrystalline quartz according to their decreasing order of abundance. The paragenetic sequence of the studied phosphorites is as follows: fluorapatite, collophane then followed by dahllite. The redox-sensitive trace elements, its ratios, authigenic uranium as well as Fe/Ti can be signifying the redox conditions. Also, they revealed that the study rocks are deposited under the oxic to anoxic environment coupled with hydrothermal solution. The trace and rare earth elements are generally associated with phosphatic rocks. Thus, the phosphatic rocks of Um El-Huwtat mine, Quseir can be considered as sources of trace and rare earth elements. Also, pyrite can be considered as another possible source for REEs. The studied phosphatic rocks characterized by light REE (LREE = 69 ppm) enrichment than heavy REE (HREE = 25 ppm). All the recoded values of the heavy metals for the study mine are higher than those in Tunisia (400.3 ppm), Morocco (571.75 ppm) and Jordan (187 ppm). The post-depositional conditions are responsible for the enrichment of U and Th and/or intensive chemical weathering in Quseir area. Enrichment Factor (EF) indicated that the enrichment or deletion of the elements may be a function of that association and the origins of the various phosphate fractions. The studied phosphatic rocks are suitable for industrialized fertilizers according to the world guides.
Highlights
The most important factors control the mineral composition of the phosphate rocks is type and source
The present study focuses on the mineralogy, petrography and geochemistry of the phosphorites at Um El-Huwtat mines of the Duwi Formation at Qusseir–Safaga region, in an effort to recognize their depositional environment and economic evolution
Morocco, (Silva et al 2010); Jordan (Batarseh and El-Hasan (2009); Average World Phosphorite (AWP) (Altschuler 1980); ASC: Average Shale Composition by Turekian and Wedepohl (1961); Soil EC: (European Commission EC 1986), Fertilizer Canada: Permissible limit established by the Canadian Food Inspection Agency (1997). n.d. not determined and U indicated that part of the U content may be occurs as tetravalent state U4+ resulting of substitution for C a2+ in the phosphate minerals during subaerial weathering (Abou El Anwar et al 2019b)
Summary
The most important factors control the mineral composition of the phosphate rocks is type and source. Clayey and calcareous materials are gangue minerals for the sedimentary phosphate origin. The most sedimentary calcareous phosphate rocks have been significant quantities of carbonates and are considered as carbonate-apatite or. Peloids are considered as authigenic or reworked in origin (El-Kammar et al 1979; Glenn and Arthur 1990). The formation of phosphorites may be carried nutrients from deep water into the photic zone (El-Tarabili 1969), formed in situ (Youssef 1957) or fluvial input (Glenn and Arthur 1990). The Egyptian phosphates are shallow marine sediments, whereas the maximum thickness was associated with a transgressive shoreline
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