Genesis of Soils from Bauxite in Southeastern Brazil: Resilication as a Soil-Forming Process

Mateus, Ana Carolina Campos; Oliveira, Fábio Soares de; Varajão, Angélica Fortes Drummond Chicarino; Soares, Caroline Cibele Vieira

doi:10.1590/18069657rbcs20160507

Cited by 10 publications

(9 citation statements)

References 29 publications

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“…In tropical soils, secondary aluminous clays, such as gibbsite and kaolinite, form a second group of mineral constituents in addition to Fe oxides, which are highly related to each other. Gibbsite as the most important Al hydroxide has a similar structure as the octahedral layer of kaolinite 25 and might form upon desilication of kaolinite 26 – 28 or even be transformed back to kaolinite through resilication 29 , 30 . Studying the selective contribution of these aluminous clays and pedogenic Fe oxides to OM stabilization in soils under field conditions thus requires distinct combinations in the content of both mineralogical groups under similar environmental conditions including climatic and geochemical properties.…”

Section: Introductionmentioning

confidence: 99%

Iron oxides and aluminous clays selectively control soil carbon storage and stability in the humid tropics

Kirsten

Mikutta

Vogel

et al. 2021

Sci Rep

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Clay minerals and pedogenic metal (oxyhydr)oxides are the most reactive soil mineral constituents controlling the long-term persistence of organic carbon (OC) in terrestrial ecosystems. However, their co-occurrence in most soils complicates direct assessment of their individual contribution to OC persistence. Making use of unique mineralogical combinations in soils located in the East Usambara Mountains of Tanzania, we disentangled the contribution of clay-sized aluminous minerals (kaolinite, gibbsite) and pedogenic Fe (oxyhydr)oxides (predominant goethite and hematite) on OC storage and stabilization under natural forests and croplands. Topsoil samples, varying in contents but not types of aluminous clays and pedogenic Fe (oxyhydr)oxides, were identified by selective extractions, X-ray diffraction, and Mössbauer spectroscopy. Associated abundance of particulate and mineral-associated organic matter (OM) was quantified by density fractionation and their changes during land-use conversion were determined as a measure of OC persistence. Additionally, we assessed the resistance of OC to chemical oxidation as well as microbial decomposition in a 50-day laboratory incubation. We found that the ratio of pedogenic Fe to aluminous clay is more consequential for OC storage and stabilization than their individual contents, despite the fact that Fe (oxyhydr)oxides generally exert a stronger impact on OC than aluminous clays. Conjunction of large amounts of Fe (oxyhydr)oxides with low aluminous clay contents caused the strongest accumulation of mineral-associated OC, a low soil respiration, high OC stability against chemical oxidation, and high OC persistence during land-use change. Our study suggests that certain mineralogical combinations in the humid tropics alleviate OM losses during land conversion because of the strong and selective mineral control on OC stabilization, particular if the weight ratio of pedogenic Fe to aluminous clay exceeds the threshold range of 0.44‒0.56.

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Section: Introductionmentioning

confidence: 99%

Iron oxides and aluminous clays selectively control soil carbon storage and stability in the humid tropics

Kirsten

Mikutta

Vogel

et al. 2021

Sci Rep

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“…While gibbsite is the main mineral at the top of the lateritic profile together with hematite and goethite, it is found restricted to the base of the BTC, reinforcing that it is the main source of its constituents. Resilication was probably the main process transforming gibbsite into kaolinite, as suggested by Dangić (1985), Lucas et al (1993), Liu et al (2010) and Mateus et al (2017), while the source of silica was from the rather unknown massive ancient forest (Lucas et al 1993).…”

Section: Discussionmentioning

confidence: 99%

The Belterra Clay on the bauxite deposits of Rondon do Pará, Eastern Amazon

2018

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Bauxite deposits in the Amazon region are commonly covered by yellowish clays which can reach up to 25m thick, known as Belterra Clay (BTC). In Rondon do Pará, Eastern Amazon, BTC is 13m thick and covers world-class bauxite reserves. Three pilot bauxite mines were investigated in Rondon do Pará for an initial characterization of the local BTC. In discordant contact with the lateritic profile, the BTC has reddish brown colors at its base to ocher tones towards the top. It has a massive structure with silt-clayey texture and nodular bauxitic fragments at its base. Rietveld mineral quantification of the material attests that it is dominated by kaolinite, with goethite, gibbsite, hematite, anatase and residual quartz. The thermal behavior of the material also confirms its mineralogical composition. Kaolinite is of low structural order, which was considered the main difficulty in the application of the Rietveld method. Goethite has up to 33 mol% of Al. As observed by scanning electron microscopy (SEM), the minerals represent pseudo-hexagonal crystals measuring from 150 to 700 nm. The BTC in the studied area is correlated to BTC on others bauxitic deposits of the Amazon region, suggesting this material experienced the same genesis and geological evolution, probably during the Pliocene.

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“…Em sistemas naturais, sob diferentes condições de pH, a caulinita, gibbsita e VHE coexistem na fração argila dos solos, enquanto sob condições de pH ácido, podem ocorrer a descloritização (substituição dos polímeros) e transformação da VHE em vermiculita (Azevedo & Vidal-Torrado, 2009). Outra possibilidade pode estar associada à reincorporação de sílica no sistema devido a mudanças ambientais, que desestabiliza alguns minerais existentes, como gibbsita, e outros são neoformados, como caulinita (Mateus et al, 2017).…”

Section: Mineralogia Da Fração Argilaunclassified

Estágio pedogeoquímico da cobertura superficial de área fonte de depósitos de colúvio - Superfície de cimeira de Pinhão/Guarapuava, Paraná

et al. 2020

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Os estudos relacionados às caracterizações de solos e formações superficiais frequentemente utilizam-se da abordagem pedogeoquímica para fornecer bases sobre os processos envolvidos na transformação do material parental, a relação entre as características geológicas, tipo e intensidade dos processos intempéricos. Nesse contexto, o presente trabalho apresenta os resultados da mineralogia das formações superficiais alóctonee autóctone da Superfície de Cimeira de Pinhão/Guarapuava, visando a inferência do estágio pedogeoquímico da cobertura superficial. Para tal, foi realizada a técnica de difração de Raios - X (DRX), utilizando-se do método de lâmina orientada, calcinada eglicolada para a fração argila e o método do pó para as frações areia, silte e argila. Os horizontes pedoestratigráficos analisados foram: CA (topo e base), 2CAb (topo e base), 3CAb (base), 4BCb (topo e base) e 5Bb (centro). O DRX foi semelhante na fração argila para todos os horizontes pedoestratigráficos analisados, compostos por caulinita, gibbsita, goethita e vermiculita, no entanto, no horizonte 3BCb não foi visualizada a presença da goethita. Para o método do pó foram constatados minerais do grupo dos filossilicatos, representados pela vermiculita e caulinita, bem como tectossilicatos, com a presença do quartzo e os óxidos, hidróxidos e oxi-hidróxidos de Fe, Al e Ti, que neste caso, referem-se aos reflexos da gibbsita, hematita, goethita, ferrihidrita, magnetita, maghemita, anatásio, rutilo e ilmenita. A constituição mineralógica dos materiais sugere a atuação dos processos de hidrólise e oxi-redução, indicando que tanto a área fonte dos depósitos de colúvio quanto do paleossolo se encontra no estágio pedogeoquímicofersialítico, o que equivale a materiais em estágio moderado de intemperismo.

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Genesis of Soils from Bauxite in Southeastern Brazil: Resilication as a Soil-Forming Process

Cited by 10 publications

References 29 publications

Iron oxides and aluminous clays selectively control soil carbon storage and stability in the humid tropics

Iron oxides and aluminous clays selectively control soil carbon storage and stability in the humid tropics

The Belterra Clay on the bauxite deposits of Rondon do Pará, Eastern Amazon

Estágio pedogeoquímico da cobertura superficial de área fonte de depósitos de colúvio - Superfície de cimeira de Pinhão/Guarapuava, Paraná

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