Microbially mediated iron ore formation, Silicic Superunit, Rudabánya, Hungary

Bodor, Sarolta; Polgári, Márta; Szentpétery, Ildikó; Földessy, János

doi:10.1016/j.oregeorev.2015.08.005

Cited by 9 publications

(2 citation statements)

References 15 publications

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“…Continental ironstones are predominantly of fluvial, alluvial, or lacustrine origin, including the entire spectrum from ferruginous mudstone to conglomerate [1,22,24]. A thorough investigation of these deposits is essential for the reconstruction of paleoenvironmental conditions of mineral formation [18,25,26], in addition to their commercial importance [22,27,28]. Fluvial, alluvial, lacustrine, or bog ironstones remain poorly understood, although they bear signs of global geological events [29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Depositional Conditions of Cretaceous Ironstones Deposit in the Chulym-Yenisey Basin (Western Siberia)

et al. 2021

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This study reconstructs the depositional conditions of ironstones within the Chulym-Yenisey basin and assesses the iron source. The detrital minerals of the studied deposits include quartz and feldspar. The authigenic minerals are goethite, siderite, aragonite, dolomite, calcite, apatite, barite, and pyrite. The clay components include minerals of the chlorite group (possible chamosite), nontronite, kaolinite, illite, and beidellite. Local bacterial sulfate reduction led to the formation of pyrite framboids in siltstone layers. The subsequent diagenetic iron reduction promoted the formation of chamosite from siderite. The goethite precipitation occurred in an oxidic aqueous environment. The Cretaceous continental sediments of the Ilek and Kia Formations of the Chulym-Yenisei depression consist of fine- and medium-grained, cross-stratified, poorly sorted litho-feldspatho-quartzose sandstones of fluvial channel origin alternating with bluish-gray siltstones and ironstones of floodplain–lacustrine–bog origin. Thin layers of iron-bearing rocks within siltstones formed in meromictic waters. The changes in geochemical proxies demonstrate fluctuations of paleoenvironmental conditions within the Cretaceous sequence. Siltstones and sandstones formed under humid and arid conditions, respectively. The primary iron source for sediments of the Chulym-Yenisey depression was determined as volcanogenic and igneous rocks of the Altai-Sayan mountainous region.

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Section: Introductionmentioning

confidence: 99%

Depositional Conditions of Cretaceous Ironstones Deposit in the Chulym-Yenisey Basin (Western Siberia)

et al. 2021

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“…This model was used successfully to detect the formation of iron ore in Rudabánya, Hungary (Bodor et al, 2016) and in the study of microbial Mn formation in the vicinity of ophiolites in the Abadeh-Tashk region of Iran (Rajabzadeh et al, 2017). The method was also used to estimate the time necessary for melting after the last glacial period in the Neoproterozoic Otavi Formation in Namibia, where climatic changes responsible for the melting were studied in the iron-biomat layers (Gyollai et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Microbially Mediated Ore-Forming Processes and Cell Mineralization

Polgári¹,

Gyollai²,

Fintor³

et al. 2019

Front. Microbiol.

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Sedimentary black shale-hosted manganese carbonate and oxide ores were studied by high-resolution in situ detailed optical and cathodoluminescence microscopy, Raman spectroscopy, and FTIR spectroscopy to determine microbial contribution in metallogenesis. This study of the Urucum Mn deposit in Brazil is included as a case study for microbially mediated ore-forming processes. The results were compared and interpreted in a comparative way, and the data were elaborated by a complex, structural hierarchical method. The first syngenetic products of microbial enzymatic oxidation were ferrihydrite and lepidocrocite on the Fe side, and vernadite, todorokite, birnessite, and manganite on the Mn side, formed under obligatory oxic (Mn) and suboxic (Fe) conditions and close to neutral pH. Fe- and Mn-oxidizing bacteria played a basic role in metallogenesis based on microtextural features, bioindicator minerals, and embedded variable organic matter. Trace element content is determined by source of elements and microbial activity. The present Urucum (Brazil), Datangpo (China), and Úrkút (Hungary) deposits are the result of complex diagenetic processes, which include the decomposition and mineralization of cell and extracellular polymeric substance (EPS) of Fe and Mn bacteria and cyanobacteria. Heterotrophic cell colonies activated randomly in the microbialite sediment after burial in suboxic neutral/alkaline conditions, forming Mn carbonates and variable cation-bearing oxides side by side with lithification and stabilization of minerals. Deposits of variable geological ages and geographical occurrences show strong similarities and indicate two-step microbial metallogenesis: a primary chemolithoautotrophic, and a diagenetic heterotrophic microbial cycle, influenced strongly by mineralization of cells and EPSs. These processes perform a basic role in controlling major and trace element distribution in sedimentary environments on a global level and place biogeochemical constraints on the element content of natural waters, precipitation of minerals, and water contaminants.

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