Studies of normative mineralogy and rare earth elements geochemistry of the Gazanjeh bauxite deposit, southeast of Mahabad, NW Iran

The Gazanjeh bauxite deposit (SE Mahabad, West-Azarbaidjan province) is a typical residual sedimentary deposit with dolomitic limestone host rock of Permian age in northwestern Iran. Calculations of normative values of minerals using obtained results from XRD and XRF analyses in a selected profile indicate that diaspore, hematite, and pyrophyllite were major mineralogical phases of this deposit and include 71.73 to 94.66 % of mineralogical composition of ores, approximately. Based on normative values of minerals, this deposit was formed from two-type ores, (1) clayey bauxite and (2) iron-rich bauxite. Based upon chemical analyses, REE values vary in the ores from 30.14 to 379.55 ppm. Values of La/Y, Eu/Eu*, and Ce/Ce* in the ores are within the ranges of 0.33-3.16, 0.57-1.36, and 0.87-7.05, respectively. Combination of the obtained results from investigation of trend of lanthanides changes and elemental ratios in the selected profile suggest that factors such as change in physico-chemical conditions of depositional environment (pH and Eh), fluctuations in level of groundwaters table, degree of complexation with carbonatic lighands, difference in the stability of lanthanides-bearing minerals, and mineral control have played the important role in distribution and mobilization of REEs during formation and development of the studied bauxitic ores.