صفحه محصول - پاورپوینت جامع با عنوان ژئوشیمی عناصر نادر خاکی در سنگ فسفاتی رسوبی

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بسم الله الرحمن الرحیم موضوع: ژئوشیمی عناصر نادر خاکی در سنگ فسفاتی رسوبی Introduction: During recent years, geochemistry of rare earth elements (REEs) has proved to be one of the best tools for determining conditions of depositional environments and understanding of formation mechanism of sedimentary phosphatic rocks, and hence has received worldwide attention by many researchers. Distribution patterns of REEs and variations of anomaly values of Eu and Ce in phosphatic sedimentary rocks are highly dependent upon various factors including conditions of the depositional environment and the degree of interaction between seawaters and land-derived detrital materials (Khan et al., 2012). Factors like weathering, diagenesis, and metamorphism can remarkably influence the concentration of REEs and their distribution patterns in phosphatic rocks (McArthur and Walsh, 1984). The results of recent researches revealed that geochemical investigations of REEs in sedimentary phosphatic rocks can furnish valuable information on paleo-seawaters and/or diagenetic fluids (e.g. Shields and Stille, 2001; Zhu et al., 2014; Muscente et al., 2014; Xin et al., 2016; Auer et al., 2017; Zhu and Jiang, 2017). The phosphatic sedimentary deposits in Iran were developed temporally in six discrete periods: (1) Spatially, thLower Cambrian, (2) Ordovician-Silurian, (3) Upper Devonian, (4) Upper Cretaceous, (5)Paleocene, and (6) Eocene-Oligocene. ese deposits are widely spread within five structural zones: (1) Central Iran, (2) Alborz-Azarbaidjan, (3) Gorgan-Rasht, (4) Folded Zagros, and (5) Sanandaj-Sirjan (Namadmalian et al., 1998). The Lower Cambrian phosphatic deposits in the Gorgan-Rasht Zone contain an average of 11 wt% P2O5 and reserves exceeding 66 million tons (Namadmalian et al., 1998), and extend over 60 km with varying thicknesses between 2.2 and 5 m. Mineralogically, the principal constituent minerals present in these deposits are calcite, fluor-apatite, dolomite, quartz, pyrite, muscovite, and illite (Abedini et al., 2012).