Mineralogy and geochemistry of corundum-bearing metabauxite-laterite from Heydarabad, SE Urmia, NW Iran

The Heydarabad bauxite-laterite deposit is located in 63 km southeast of Urmia city.This ore deposit occurs as a concordant layer within the boundaries of Upper Permian and Lower Triassic carbonate units (limestone and dolomite), although it has been suffered some tectonic displacements along its direction. The studied horizon varies from 15-20 m in thickness and has an east-west trend with a length of 3.5 km. This deposit consists primarily of two parts of dark and light in color. The former is rich in hematite and corundum, (upper horizon) and the latter in phyllo-aluminosilicates (lower horizon) with an gradual boundary, respectively. Common textures are mostly pisolitic, nodular, oolitic and massive. Based on the microscopic studies and XRD analysis, the main mineral components are hematite, diaspore, chloritoid, and corundum.On the other hand, chlorite, rutile, magnetite and pyrite are found as accessory phases. The Heydarabad bauxite-laterite horizon is different from those occurred into the Iran-Himalayan belt based on the absence of boehmite, kaolinite and other clay minerals, and the abundance of corundum, chloritoid and chlorite. The geological and mineralogical evidences indicated that a thermal metamorphic event was responsible for the formation of this special mineralogical composition after bauxitization processes. Based on geological, mineralogical, and chemical characteristics, it can be proposed that the probable parent rocks for the Heydarabad bauxite are mafic sills and diabasic dykes. Due to considerable accumulation of minerals which their hardness is greater than 6, this ore deposit can be presented as a potential for abrasive applications.