H. Khalilzadeh; A. A. Calagari; A. Abedini; H. Rahimpour-Bonab
Abstract
Boket residual horizon is located in ~15 km northeast of Ajabshir, East-Azarbaijan province. This horizon was developed as stratiform lenses along the contact of Ruteh (middle-upper Permian) and Elika (Triassic) carbonate formations. The ores within this horizon display pelitomorphic, micro-granular, ...
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Boket residual horizon is located in ~15 km northeast of Ajabshir, East-Azarbaijan province. This horizon was developed as stratiform lenses along the contact of Ruteh (middle-upper Permian) and Elika (Triassic) carbonate formations. The ores within this horizon display pelitomorphic, micro-granular, micro-ooidic, pseudo-porphyritic, ooidic, pisoidic, pseudo-breccia, and nodular textures. Based on geochemical data, the ores within this horizon are divided into five types, (1) ferritic laterite, (2) bauxitic laterite, (3) kaolinitic laterite, (4) ferritic kaolinite, and (5) laterite. Comparison of distribution patterns of elements across a selected profile indicates the effective role of Al and Ti in distributing and concentrating of Zr, Ga, Nb, Th, V, and HREEs within the ores. Incorporation of data obtained from petrographical and geochemical studies shows that the ores have authigenic origin. Furthermore, factors such as chemical variations of weathering solutions, fixation in neomorphic phases, existing in resistant minerals, heterogeneity of protolith, differences in the degree of weathering intensity, and adsorption processes coupled with weak drainage, diagenesis, dynamic pressures, and fluctuation of underground water table played crucial roles in distribution and development of ores within this horizon. The most notable geochemical characteristics of the ores (except in kaolinitic laterite) is the greater mobility of LREEs relative to HREEs during weathering processes. This abnormal behavior within the horizon could be related to factors such as differences in stability of primary minerals containing REEs, the pH variation (from 6.7 to 7.8) of weathering solutions, and moderate degree of evolution of the profile.
A. Abedini; A. A. Calagari
Abstract
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. ...
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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.