The role of microorganisms in the formation of a stalactite in Botovskaya Cave, Siberia – paleoenvironmental implications

Abstract. Calcitic speleothems in caves can form through abiogenic or biogenic processes, or through a combination of both. Many issues conspire to make the assessment of biogenicity difficult, especially when focusing on old speleothem deposits. This study reports on a multiproxy analysis of a Siberian stalactite, combining high-resolution microscopy, isotope geochemistry and microbially enhanced mineral precipitation laboratory experiments. The contact between growth layers in a stalactite exhibits a biogenic isotopic signature; coupled with morphological evidence, this supports a microbial origin of calcite crystals. SIMS δ13C data suggest that microbially mediated speleothem formation occurred repeatedly at short intervals before abiotic precipitation took over. The studied stalactite also contains iron and manganese oxides that have been mediated by microbial activity through extracellular polymeric substance (EPS)-influenced organomineralization processes. The latter reflect paleoenvironmental changes that occurred more than 500 000 yr ago, possibly related to the presence of a peat bog above the cave at that time. Microbial activity can initiate calcite deposition in the aphotic zone of caves before inorganic precipitation of speleothem carbonates. This study highlights the importance of microbially induced fractionation that can result in large negative δ13C excursions. The microscale biogeochemical processes imply that microbial activity has only negligible effects on the bulk δ13C signature in speleothems, which is more strongly affected by CO2 degassing and the host rock signature.

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The role of microorganisms on the formation of a stalactite in Botovskaya Cave, Siberia – palaeoenvironmental implications

Biogeosciences Discussions ◽

10.5194/bgd-10-6563-2013 ◽

2013 ◽

Vol 10 (4) ◽

pp. 6563-6603

Author(s):

M. Pacton ◽

S. F. M. Breitenbach ◽

F. A. Lechleitner ◽

A. Vaks ◽

C. Rollion-Bard ◽

...

Keyword(s):

Microbial Activity ◽

Manganese Oxides ◽

Extracellular Polymeric Substances ◽

Isotope Geochemistry ◽

Isotopic Signature ◽

Morphological Evidence ◽

Calcite Deposition ◽

Inorganic Precipitation ◽

Co2 Degassing

Abstract. Calcitic speleothems in caves can form through abiogenic, biogenic, or a combination of both processes. Many issues conspire to make the assessment of biogenicity difficult, especially when focusing on old speleothem deposits. This study reports a multiproxy analysis of a Siberian stalactite, combining high-resolution microscopy, isotope geochemistry and microbially enhanced mineral precipitation laboratory experiments. The contact between growth layers in a stalactite exhibits a biogenic isotopic signature; coupled with morphological evidence this supports a microbial origin of calcite crystals. SIMS δ13C data suggest that microbially mediated speleothem formation occurred repeatedly for short intervals before abiotic precipitation took over. The studied stalactite also contains iron and manganese oxides that have been mediated by microbial activity through extracellular polymeric substances (EPS)-influenced organomineralization processes. The latter reflect palaeoenvironmental changes that occurred more than 500 000 yr ago, possibly related to the presence of a peat bog above the cave at that time. Microbial activity can initiate calcite deposition in the aphotic zone of caves before inorganic precipitation of speleothem carbonates. This study highlights the importance of microbially induced fractionation that can result in large negative δ13C excursions. The micro-scale biogeochemical processes imply that microbial activity has only negligible effects on the bulk δ13C signature in speleothems, which is more strongly affected by CO2 degassing and the hostrock signature.

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Trace Metal Contamination in Sediments from U.K. Estuaries: An Empirical Evaluation of the Role of Hydrous Iron and Manganese Oxides

Estuarine Coastal and Shelf Science ◽

10.1006/ecss.1999.0573 ◽

2000 ◽

Vol 50 (3) ◽

pp. 355-371 ◽

Cited By ~ 65

Author(s):

A. Turner

Keyword(s):

Trace Metal ◽

Metal Contamination ◽

Manganese Oxides ◽

Empirical Evaluation ◽

Trace Metal Contamination ◽

Iron And Manganese

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Ultrasound-Assisted Citric Acid Extraction of Zinc in Plateau Red Soil and Tessier Speciation Study

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.726-731.4464 ◽

2013 ◽

Vol 726-731 ◽

pp. 4464-4467

Author(s):

Wei Wei ◽

Xue Jin Zhou ◽

Yun Tao Gao

Keyword(s):

Heavy Metal ◽

Citric Acid ◽

Manganese Oxides ◽

Red Soil ◽

Extraction Rate ◽

Acid Extraction ◽

Speciation Study ◽

Ultrasonic Assisted ◽

Ultrasound Assisted ◽

Iron And Manganese

Taking plateau red soil as research object, using the ultrasonic-assisted organic acid extraction the heavy metal zinc in it, and analyze the form of zinc. Results showed that the extraction rate can reach 68%, with the increase of time, the extraction effect of zinc is obviously enhanced in this method. Ultrasonic-assisted citric acid extraction soil can increase the extraction rate of exchangeable, bound to carbonates and bound to iron and manganese oxides relatively.

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More than redox, biological organic ligands control iron isotope fractionation in the riparian wetland

Scientific Reports ◽

10.1038/s41598-021-81494-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Elaheh Lotfi-Kalahroodi ◽

Anne-Catherine Pierson-Wickmann ◽

Olivier Rouxel ◽

Rémi Marsac ◽

Martine Bouhnik-Le Coz ◽

...

Keyword(s):

Redox Reactions ◽

Isotope Fractionation ◽

Isotopic Fractionation ◽

Isotopic Signature ◽

Organic Ligands ◽

Riparian Wetland ◽

Fe Isotopes ◽

Preferential Binding ◽

Isotope Systematics

AbstractAlthough redox reactions are recognized to fractionate iron (Fe) isotopes, the dominant mechanisms controlling the Fe isotope fractionation and notably the role of organic matter (OM) are still debated. Here, we demonstrate how binding to organic ligands governs Fe isotope fractionation beyond that arising from redox reactions. The reductive biodissolution of soil Fe(III) enriched the solution in light Fe isotopes, whereas, with the extended reduction, the preferential binding of heavy Fe isotopes to large biological organic ligands enriched the solution in heavy Fe isotopes. Under oxic conditions, the aggregation/sedimentation of Fe(III) nano-oxides with OM resulted in an initial enrichment of the solution in light Fe isotopes. However, heavy Fe isotopes progressively dominate the solution composition in response to their binding with large biologically-derived organic ligands. Confronted with field data, these results demonstrate that Fe isotope systematics in wetlands are controlled by the OM flux, masking Fe isotope fractionation arising from redox reactions. This work sheds light on an overseen aspect of Fe isotopic fractionation and calls for a reevaluation of the parameters controlling the Fe isotopes fractionation to clarify the interpretation of the Fe isotopic signature.

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Strategies for EELS Data Analysis. Introducing UMAP and HDBSCAN for Dimensionality Reduction and Clustering

Microscopy and Microanalysis ◽

10.1017/s1431927621013696 ◽

2021 ◽

pp. 1-14

Author(s):

Javier Blanco-Portals ◽

Francesca Peiró ◽

Sònia Estradé

Keyword(s):

Dimensionality Reduction ◽

Clustering Analysis ◽

Manganese Oxides ◽

Spatial Clustering ◽

State Of The Art ◽

Core Loss ◽

Nonnegative Matrix ◽

Case Scenario ◽

Electron Energy Loss ◽

Iron And Manganese

Hierarchical density-based spatial clustering of applications with noise (HDBSCAN) and uniform manifold approximation and projection (UMAP), two new state-of-the-art algorithms for clustering analysis, and dimensionality reduction, respectively, are proposed for the segmentation of core-loss electron energy loss spectroscopy (EELS) spectrum images. The performances of UMAP and HDBSCAN are systematically compared to the other clustering analysis approaches used in EELS in the literature using a known synthetic dataset. Better results are found for these new approaches. Furthermore, UMAP and HDBSCAN are showcased in a real experimental dataset from a core–shell nanoparticle of iron and manganese oxides, as well as the triple combination nonnegative matrix factorization–UMAP–HDBSCAN. The results obtained indicate how the complementary use of different combinations may be beneficial in a real-case scenario to attain a complete picture, as different algorithms highlight different aspects of the dataset studied.

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Enhancing Cd(II) Adsorption on Rice Straw Biochar by Modification of Iron and Manganese Oxides

SSRN Electronic Journal ◽

10.2139/ssrn.3958698 ◽

2021 ◽

Author(s):

Wen-Tao TAN ◽

Hang ZHOU ◽

Shang-Feng TANG ◽

Peng ZENG ◽

Jiao-Feng GU ◽

...

Keyword(s):

Rice Straw ◽

Manganese Oxides ◽

Rice Straw Biochar ◽

Iron And Manganese

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Pb-Nd-Sr Isotope Geochemistry of Metapelites from the Iberian Pyrite Belt and Its Relevance to Provenance Analysis and Mineral Exploration Surveys

Economic Geology ◽

10.5382/econgeo.4869 ◽

2021 ◽

Author(s):

Filipa Luz ◽

António Mateus ◽

Ezequiel Ferreira ◽

Colombo G. Tassinari ◽

Jorge Figueiras

Keyword(s):

Isotope Geochemistry ◽

Mineral Exploration ◽

Hanging Wall ◽

Massive Sulfide ◽

Iberian Pyrite Belt ◽

Isotopic Signature ◽

Sr Isotope ◽

Provenance Analysis ◽

Basement Rocks ◽

World Class

Abstract The boundary in the Iberian Pyrite Belt is a world-class metallogenic district developed at the Devonian-Carboniferous boundary the Iberian Variscides that currently has seven active mines: Neves Corvo (Cu-Zn-Sn) and Aljustrel (Cu-Zn) in Portugal, and Riotinto (Cu), Las Cruces (Cu), Aguas Teñidas (Cu-Zn-Pb), Sotiel-Coronada (Cu-Zn-Pb), and La Magdalena (Cu-Zn-Pb) in Spain. The Iberian Pyrite Belt massive sulfide ores are usually hosted in the lower sections of the volcano-sedimentary complex (late Famennian to late Visean), but they also occur in the uppermost levels of the phyllite-quartzite group at the Neves Corvo deposit, stratigraphically below the volcano-sedimentary complex. A Pb-Nd-Sr isotope dataset was obtained for 98 Iberian Pyrite Belt metapelite samples (from Givetian to upper Visean), representing several phyllite-quartzite group and volcano-sedimentary complex sections that include the footwall and hanging-wall domains of ore horizons at the Neves Corvo, Aljustrel, and Lousal mines. The combination of whole-rock Nd and Sr isotopes with Th/Sc ratios shows that the siliciclastic components of Iberian Pyrite Belt metapelites are derived from older quartz-feldspathic basement rocks (–11 ≤ εNdinitial(i) ≤ –8 and (87Sr/86Sr)i up to 0.727). The younger volcano-sedimentary complex metapelites (upper Tournaisian) often comprise volcanic-derived constituents with a juvenile isotopic signature, shifting the εNdi up to +0.2. The Pb isotope data confirm that the phyllite-quartzite group and volcano-sedimentary complex successions are crustal reservoirs for metals found in the deposits. In Neves Corvo, where there is more significant Sn- and Cu-rich mineralization, the higher (206Pb/204Pb)i and (207Pb/204Pb)i values displayed by phyllite-quartzite group and lower volcano-sedimentary complex metapelites (up to 15.66 and 18.33, respectively) suggest additional contributions to the metal budget from a deeper and more radiogenic source. The proximity to Iberian Pyrite Belt massive sulfide ore systems hosted in metapelite successions is observed when (207Pb/204Pb)i >15.60 and Fe2O3/TiO2 or (Cu+Zn+Pb)/Sc >10. These are important criteria that should be considered in geochemical exploration surveys designed for the Iberian Pyrite Belt.

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