Geological,geochemical, and mineralogical characteristics of the Mandan and Deh-now bauxite deposits,Zagros Fold Belt,Iran |
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| Affiliation: | 1. Center for Electron Nanoscopy, Technical University of Denmark, 2800 Kongens Lyngby, Denmark;2. Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, Zografou Campus, 15784 Athens, Greece;3. Department of Geology & Mineral Engineering, Norwegian University of Science & Technology, 7491 Trondheim, Norway;4. Department of Physics, University of Ioannina, 45110 Ioannina, Greece;5. ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany;6. Karlsruhe Institute of Technology, Institute for Chemical Technology and Polymer Chemistry, Kaiserstrasse 12, 76131 Karlsruhe, Germany;7. KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, 3001 Leuven, Belgium;8. Department of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece;1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;2. Guizhou Geological Survey, Bureau of Geology and Mineral Exploration and Development of Guizhou Province, Guiyang 550005, China;1. Department of Sciences, University of Basilicata, viale dell''Ateneo Lucano 10, 85100 Potenza, Italy;2. CNR — Istituto di Metodologie per l''Analisi Ambientale, c/da S. Loya, 85050, Tito Scalo, Italy;3. CNR — Istituto di Geoscienze e Georisorse, via Ferrara 1, 27100 Pavia, Italy |
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| Abstract: | The Mandan and Deh-now bauxite deposits are located 40 km northeast of the Dehdasht city in the Zagros simply fold belt. These deposits occur in eroded major NW–SE trending anticlines and occupy karst cavities near or at the boundary between the Sarvak and Ilam Formations. Local uplifts at the end of the Cenomanian and the mid-Turonian caused erosion and karstification of the Sarvak Formation. These unconformities in the Upper Cretaceous favoured the formation and enrichment of bauxite deposits in the Zagros fold belt. The bauxite sequence in the Mandan deposit consists of white, gray, black, pisolitic, red, and yellow bauxites. This sequence was repeated in the Deh-Now area, but without gray and black bauxites. The present mineralogical studies of the Sarvak Formation and the Mandan and Deh-now bauxite deposits indicate oxidizing to reducing conditions during the Upper Cretaceous in the Zagros fold belt, which had a significant effect on the compositions of the bauxites. At least two phases of bauxitization can be distinguished in the study area: (i) an oxidizing phase represented by boehmite, diaspore, hematite and kaolinite; and (ii) a reducing phase represented by pyrite and chlorite. Geochemical data show that trace elements, like Zr, Hf, Nb, Ta, Th, and U, were enriched during bauxitization. The bauxite deposits and carbonate rocks show similar REE patterns, namely they are enriched in REEs although the LREEs are more enriched than the HREEs. Mass change calculations demonstrate that Mg, Mn, Ca, K, and P2O5 were leached out of the weathered system whereas Al, Fe, and Si become concentrated in the residual system. This study indicates that the Mandan and Deh-now deposits are karst-type bauxites formed by karstification and weathering of the Sarvak Formation. |
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