Immobile elements and mass changes geochemistry at Sar-Faryab bauxite deposit, Zagros Mountains, Iran

Abstract

The Sar-Faryab bauxite deposit is located in 250 km east of Ahvaz city in southwestern Iran. Structurally the deposit located in the Zagros Simply Folded Mountain Belt. Outcrops of the bauxite horizons in the area are distributed irregularly over an area of about 20 km 2 but have fairly uniform thickness averaging 1 to 1.5 m. The Sar-Faryab bauxite is situated in NW–SE trending Mandan anticline and occurs in karst horizons near or at the boundary between the Sarvak and Ilam Formations. Based on field observation, mineralogy and stratigraphy an unconformity during Cenomanian–Turonian times has exposed the Sarvak Limestone to karst weathering and the layers of Marly Limestone, Argillite, Oolitic–Pisolitic, Yellow, Red and White Bauxite were formed and accumulated in the karstic areas. 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. In this way fifteen samples were collected from seven layers of the deposit for geochemical studies using XRF. Geochemical data 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 Sar-Faryab bauxite was the underlying Marly limestone (Sarvak Formation). The karst bauxite deposits are probably of authigenic origin, as evidenced by their geochemical characteristics, lithologic associations, textural and mineralogy.