Abstract

The Dopolan deposit is a Mediterranean-type bauxite located in the Zagros Fold-Thrust Zone, Iran. This deposit consists of five lithological members including iron-rich, clay-rich, oolitic, pisolitic and organic matter-containing bauxites. The mineralogy of the deposit includes diaspore, boehmite, and kaolinite, nacrite, with minor pyrite, anatase and rutile. Geochemical studies show that light rare earth elements (LREEs) are enriched relative to heavy rare earth elements (HREEs) in all members, supporting an authigenic origin. Mass changes based on Ti as an immobile element indicate that conventionally-immobile elements (Al, Nb, Ta, Zr, Hf) are enriched in situ in the residual units, whereas mobile elements (K, Ca, Si) were depleted during bauxitization. This study shows that the Khaneh-Kat argillitic dolomite is the likely parent rock. The delta O-18 (7.63 parts per thousand to 9.35 parts per thousand) and delta D values (-49.91 parts per thousand to -66.49 parts per thousand) for kaolinite in the bauxite samples suggest equilibration with meteoric waters which supports a supergene origin. Bauxitization occurred in a warm climate with relatively constant isotopic composition suggesting climate stability during the development of bauxite horizons and remobilization of Al (with formation of secondary boehmite). The delta C-13 values of calcite (-7.3 parts per thousand) in the bauxite support the idea that the Khaneh-Kat Formation has experienced post-depositional isotope exchange with meteoric waters during the karstification process.