Geology, Mineralogy and Geochemistry of Bauxitic- Lateritic Horizon in the Deilaman- Eshkevarat Area, Central Alborz

The studied area is located in the western part of the Central Alborz structural zone and contains a bauxitic- lateritic horizon between the Elika and Shemshak formations. This horizon belongs to the middle Triassic, and croups out with E-W trend in the four regions (trends) including Zard Kuh- Loriteh, Shagol- Sangrood, Abasak- Hir, and Arsheh Kuh- Zakabar. The complete cross section of bauxitic- lateritic horizon contain dark grey pisolites in the lower part, yellowish red laterite in the middle part, and an upper part with light grey color. Kaolinite and quartz are the main mineral components of this horizon. The minerals such as diaspore, bohemite, anatase, hematite and goethite present as minor phase. The grey- colored upper and lower parts contain high grade of Al2O3 and low grade of Fe2O3 while in the middle part, high grade of Fe2O3 and low grade of Al2O3. The average grades of Al2O3, Fe2O3, SiO2 and TiO2 in the samples are in turn 35%, 14%, 35% and 5%. The maximum grades of Al2O3 in the mentioned four trends are 51%, 61%, 48% and 48%. There is a distinctive negative correlation between Al2O3 and Fe2O3, between Fe2O3 and SiO2, and between Fe2O3 and TiO2. Furthermore, there is a positive correlation between Al2O3 and TiO2. The results of laboratory investigations indicated that the best bauxitic- lateritic horizon in the studied area considering grades of major oxides is the Abasak- Hir trend.