气候变化领域集成服务门户(CCPortal): Microbial weathering signatures in lateritic ferruginous duricrusts

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DOI	10.1016/j.epsl.2020.116209
	Microbial weathering signatures in lateritic ferruginous duricrusts
	Levett A.; Vasconcelos P.M.; Gagen E.J.; Rintoul L.; Spier C.; Guagliardo P.; Southam G.
发表日期	2020
ISSN	0012821X
卷号	538
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.
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
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202722
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
推荐引用方式 GB/T 7714	Levett A.,Vasconcelos P.M.,Gagen E.J.,et al. Microbial weathering signatures in lateritic ferruginous duricrusts[J],2020,538.
APA	Levett A..,Vasconcelos P.M..,Gagen E.J..,Rintoul L..,Spier C..,...&Southam G..(2020).Microbial weathering signatures in lateritic ferruginous duricrusts.Earth and Planetary Science Letters,538.
MLA	Levett A.,et al."Microbial weathering signatures in lateritic ferruginous duricrusts".Earth and Planetary Science Letters 538(2020).