Studies of Normative Mineralogy and REE Geochemistry of Permian Residual Horizon in Northeast of Malekan, East-Azarbaidjan Province

A Permian residual horizon is located in ~30 km northeast of Malekan, which was developed as stratiform layer in Ruteh carbonate rocks. Mineralogically, this horizon includes minerals such as boehmite, diaspore, hematite, kaolinite, rutile, anatase, montmorillonite, muscovite, calcite, and chlorite. Calculations of normative values of minerals in a selective profile show that this horizon consists of five distinct lithological facies which are, from bottom to the top, (1) kaolinitic ferrite, (2) ferritic kaolin, (3) ferritic bauxite, (4) kaolin, and (5) bauxitic kaolin. Based on obtained data, it seems that the distribution of REEs in the studied profile was principally controlled by factors such as (1) Eh variations of the environment due to decomposition of organic matters, (2) the pH increase of weathering solutions by carbonate bedrocks, (3) scavenging and fixation processes, and (4) fluctuation of underground water table. Further geochemical evidence indicates that the concentration of LREEs were occurred by muscovite, Mn-oxides, and secondary phosphates (e.g., monazite, gorceixite, rhabdophane) and that of HREEs by rutile, anatase, and zircon in the studied profile.