Microbial processes and the origin of the Úrkút manganese deposit,Hungary |
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| Institution: | 1. Institute for Geochemical Research, Hungarian Academy of Sciences, 1112 Budapest, Budaörsi út 45, Hungary;2. USGS, 400 Natural Bridges Dr., Santa Cruz, CA 95060, USA;3. Mangán Ltd. Úrkút, Külterület 1, H-8409, Hungary;4. Department of Mineralogy, Geochemistry and Petrology, University of Szeged, H-6701 Szeged, P. O. Box 651, Hungary;5. Research Institute for Technical Physics And Materials Science, Hungarian Academy of Sciences, 1121 Budapest, Konkoly Thege út 29-33, Hungary;1. Géosciences Montpellier, CNRS, UMR5243, Université de Montpellier, Place Eugène Bataillon, cc 60, 34095 Montpellier, France;2. ERAMET Research, 1 Avenue Albert Einstein, 78190 Trappes, France;3. Laboratoire Geops-UMR8148, Université Paris Saclay, Bât 504, 91405 Orsay, France;4. Université des sciences et techniques de Masuku (USTM), Franceville, Gabon;5. COMILOG SA- Société du groupe Eramet, B.P. 27-28 Moanda, Gabon;1. Firat University, Department of Geological Engineering, 23119 Elazig, Turkey;2. U.S. Geological Survey, 2885 Mission St., Santa Cruz, CA 95060, USA;1. The Key Laboratory of Orogenic Belts and Crustal Evolution, Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, PR China;2. College of Engineering, Peking University, Beijing 100871, PR China |
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| Abstract: | The Transdanubian Range (Hungary, ALCAPA Unit) preserves a series of black shale-hosted Mn-carbonate deposits and cherty, Fe-rich Mn-oxide mineralized rocks associated with varicolored metalliferous claystones. Coccoid clumps (spherules), oval, tubular, and filamentous morphologies were observed by petrography, SEM-EDS, and TEM studies and are interpreted to be mineralized cellular materials. Local selective enrichment of bioessential elements (Mn, Fe, S, As, P, Mg, Ba, Sr, Co, Ce) occurs, and together with low δ13C values of the Mn carbonates also supports microbial mediated reactions. The results strongly suggest that the formation of Mn–Fe and Si minerals was associated with microbial metabolic processes. The role of aerobic chemolithoautotroph bacteria was essential in sequestering metal ions (Mn2 +, Fe2 +) from solution, which were deposited in the sediment pile and serve as a paleoenvironmental indicator of oxic conditions. These deposits are examples of, and therefore provide important criteria for identifying, non-sulphidic, oxic, microbial mineral processes. We provide a new genetic model for giant black shale-hosted Mn-carbonate deposits that involves episodic aerobic microbial processes.Although a part, if not the whole of the black shale-hosted Mn-carbonate deposits is of biogenetic-bacterial sedimentary origin, a hydrothermal/exhalative source of metals may have contributed to the formation of the deposits. An Fe–Mn-oxide chimney system is proposed to be a proximal facies to geofluid vents that occurred along fracture systems, which may have provided metals from deep-seated sources. |
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