DOI: 10.1016/j.epsl.2020.116209
论文题名: Microbial weathering signatures in lateritic ferruginous duricrusts
作者: Levett A. ; Vasconcelos P.M. ; Gagen E.J. ; Rintoul L. ; Spier C. ; Guagliardo P. ; Southam G.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 538 语种: 英语
中文关键词: biogeochemical cycling
; canga
; microbial weathering
; microfossils
; NanoSIMS
英文关键词: Aluminum oxide
; Biogeochemistry
; Chromium
; Dissolution
; Economic geology
; Grain boundaries
; Iron ores
; Landforms
; Microorganisms
; Oxide minerals
; Rare earths
; Revegetation
; Scanning electron microscopy
; Secondary ion mass spectrometry
; Soil conservation
; Soils
; Textures
; Titanium dioxide
; Weathering
; Biogeochemical cycling
; canga
; Microbial weatherings
; Microfossils
; NanoSIMS
; Iron deposits
; biogeochemical cycle
; chemical weathering
; gibbsite
; ore deposit
; pH
; precipitation (chemistry)
; Raman spectroscopy
; scanning electron microscopy
; trace element
英文摘要: Iron-rich duricrusts (canga) that blanket iron ore deposits in tropical regions in Brazil have a complex formation and evolution. The direct role of microorganisms in the biogeochemical cycling of iron and remarkably aluminium, which is critical for the preservation of these duricrusts, is becoming more apparent. In this study we combine nanoscale secondary ion mass spectrometry (NanoSIMS) with Raman spectroscopy and scanning electron microscopy to distinguish highly weathered and recycled grains, portions of which have been metasomatised by iron in solution, from new mineral precipitates within canga. Microbially-accelerated weathering of grains within canga appears to promote iron, aluminium and titanium oxide mineral dissolution. Anatase forms at the boundaries of rutile grains, highlighting titanium dissolution and re-precipitation at the mineral-scale. Titanium is absent from the authigenic cements in canga. Aqueous ferrous iron, which is sensitive to changes in the oxidation potential of the solution, readily oxidises and re-precipitates in the pore spaces in proximity to preserved microorganisms, leaving aluminium as the most abundant cation in solution. Changes in solution pH and/or organic chemistry causes aluminium to precipitate from solution as gibbsite that infills pore spaces as the final geological texture. Evidence for microbially-promoted weathering includes the fossilisation of microorganisms along grain boundaries, in which aluminium, titanium, chromium and iron are depleted. Immobile elements including titanium, chromium and thorium, associated with rounded fossilised biofilms also indicate that microorganisms have completely weathered grains and become fossilised in place, texturally replacing the grain in the process. Microorganisms also play a role in iron and aluminium precipitation, providing sites for mineral nucleation. These results highlight the microscale changes in oxidation potential, pH and organic chemistry throughout canga that are likely to be influenced by the microbiome and associated flora. Understanding the role of microorganisms in iron biogeochemical cycling will contribute to the accelerated re-cementation of iron-rich duricrusts after the completion of iron ore mining, providing a substrate for revegetation using native plant species. This study also sheds light on direct (microfossils) and indirect (biologically-influenced element mobility) biosignatures in iron-rich geological materials. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165100
Appears in Collections: 气候变化与战略
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作者单位: School of Earth and Environmental Sciences, University of Queensland, Brisbane, Queensland 4072, Australia; School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland 4001, Australia; Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Perth, Western Australia 6009, Australia
Recommended Citation:
Levett A.,Vasconcelos P.M.,Gagen E.J.,et al. Microbial weathering signatures in lateritic ferruginous duricrusts[J]. Earth and Planetary Science Letters,2020-01-01,538