The Role of Organic Matter in the Formation of High-Grade Al Deposits of the Dopolan Karst Type Bauxite, Iran: Mineralogy, Geochemistry, and Sulfur Isotope Data
| Autor: | Batoul Taghipour, Somayeh Salamab Ellahi, Mostafa Nejadhadad |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
lcsh:QE351-399.2
sulfur isotope Geochemistry Mineralogy chemistry.chemical_element engineering.material Diaspore 010502 geochemistry & geophysics 01 natural sciences Al enrichment δ34S Bioleaching Kaolinite Organic matter organic matter 0105 earth and related environmental sciences chemistry.chemical_classification lcsh:Mineralogy Geology 04 agricultural and veterinary sciences Geotechnical Engineering and Engineering Geology Sulfur pyrite Dopolan bauxite Bauxite chemistry 040103 agronomy & agriculture engineering 0401 agriculture forestry and fisheries Pyrite |
| Zdroj: | Minerals; Volume 7; Issue 6; Pages: 97 Minerals, Vol 7, Iss 6, p 97 (2017) |
| ISSN: | 2075-163X |
| DOI: | 10.3390/min7060097 |
| Popis: | Mineralogical and geochemical analyses of the Dopolan karstic bauxite ore were performed to identify the characteristics of four bauxite horizons, which comprise from top to bottom, bauxitic kaolinite, diaspore-rich bauxite, clay-rich bauxite, and pyrite-rich bauxite. Diaspore, kaolinite, and pyrite are the main minerals; böhmite, muscovite, rutile, and anatase are the accessory minerals. The main minerals of the Dopolan bauxite deposit indicate slightly acidic to alkaline reducing conditions during bauxitization. Immobile elements (Nb, Ta, Zr, Hf, and rare earth elements) are enriched in the diaspore-rich horizon, which also has the highest alumina content, whereas redox sensitive elements (e.g., Cr, Cu, Ni, Pb, Zn, Ag, U, and V) are enriched in the lowest horizon of pyrite-rich bauxite. The presence of a high content of organic matter was identified in different horizons of bauxitic ore from wet chemistry. The presence of organic matter favored Fe bioleaching, which resulted in Al enrichment and the formation of diaspore-rich bauxite. The leached Fe2+ reacted with the hydrogen sulfur that was produced due to bacterial metabolism, resulting in the formation of the pyrite-rich horizon towards the bottom of the Dopolan bauxite horizons. Biogeochemical activity in the Dopolan bauxitic ore was deduced from the reducing environment of bauxitization, and the deposition of framboidal and cubic or cubic/octahedral pyrite crystals, with large negative values of δ34S of pyrite (−10‰ to −34‰) and preserved fossil cells of microorganisms. |
| Databáze: | OpenAIRE |
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