East of Shahindezh (south of West Azarbaidjan province), as a part of Irano-Himalayan karst bauxite belt, comprises discontinuous layers and lenses of bauxite, laterite, and kaolin within the Ruteh carbonate formation (Middle- Upper Permian). The XRD analyses show that the lateritic ores have rather simple mineralogy, and consist of hematite, boehmite, and kaolinite as major phases accompanied by minor phases such as goethite, montmorillonite, diaspore, illite, chlorite, and rutile. According to petrographical considerations, it can be deduced that the ores have polycyclic nature and their evolution being largely affected by the function of diagenetic and epigenetic processes. Petrographical features along with mineral assemblages reveal that the lateritic ores were deposited almost in a vadose environment. Based on chemistry of major elements, the ores are categorized into three types; (1) bauxitic ferrite, (2) laterite, and (3) ferritic laterite. Distribution pattern of REEs normalized to chondrite displays a low degree of differentiation between LREEs and HREEs and also a weak negative anomaly for Eu during the lateritization processes. These features along with field relations and concentration values of Al, Ti, and Zr indicate a diabasic protolith for the ores. Consideration of Ce and Eu anomalies unveil that the intensity of lateritization is directly related to the pH increase of drained water, Eh variations, and fluctuation of water table. Results from geochemical data have furnished compelling evidence that buffering of underground descending acidic weathering solutions, dissimilaritis in degree of resistance against weathering among primary minerals, discrepancies in degree of stability of complexing legands, and chemical characteristics of elements are four key controlling factors for the distribution and behavior of major, minor, trace, and rare earth elements during lateritization in east of Shahindezh.
