Determination of the origin and mass change geochemistry during bauxitization process at the Hangam deposit, SW Iran

Abstract

The Hangam bauxite deposit is located in the Firouzabad region in southwestern Iran. Structurally the deposit located in the Simply Folded Belt of the Zagros Mountains. The Hangam bauxite horizon, which lies between the Sarvak and the Ilam formations, is approximately 30 meters thick and covers an area of about 1 km2. According to stratigraphical and sedimentological data a sedimentary hiatus during Cenomanian-Turonian times has exposed the Sarvak Limestone to karst weathering and the layers of carbonate argillaceous debris (Basal Marly Limestone; Ferruginous Carbonate Marl; Red Marly Limestone; White Marly Limestone) accumulated on its surface, which was partly converted to bauxite (Pisolitic Bauxite, Yellow Bauxite and Red Bauxite). Twenty four samples were collected from eight layers of the deposit for laboratorys work. Microscopic studies of thin and polished-thin sections show pelitomorphic, fluidal, and pseudobrecciated textures, all poiting to an authigenic origin for the Hangam bauxite. This study uses the geochemistry of immobile elements to trace the precursor rock of the bauxite deposit and to calculate the mass changes that took place during weathering and bauxitization. Plots of chemical data and calculation of correlation coefficients show that Al and Ti were immobile during the bauxitization process and were used for mass change calculations. Mass changes were calculated from the concentration ratio of immobile elements for the different bauxite rocks and the Sarvak Limestone. As only one linear trend is evident in the Al-Ti binary diagram and the Sarvak Limestone coincides with this trend, we concluded that the source of the Hangam bauxite was the underlying argillaceous limestone (Sarvak Formation).