Reading the climate signals hidden in bauxite

Heller, Beatrix; Riffel, Silvana Bressan; Allard, Thierry; Morin, Guillaume; Roig, Jean-Yves; Couëffé, Renaud; Aertgeerts, Geoffrey; Derycke, Alexis; Ansart, Claire; Pinna-Jamme, Rosella; Gautheron, Cécile

doi:10.1016/j.gca.2022.02.017

Cited by 19 publications

(26 citation statements)

References 87 publications

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“…Indeed, dispersed ages are generally associated with distinct U, Th, or Sm content (Figure 6). In fact, many factors are likely to influence the He content in Fe-oxides, for example, helium loss (Hofmann et al, 2017), mineral inclusions richer in He, U, or Th than Fe-oxides (Cornu et al, 2009;Vasconcelos et al, 2013;Monteiro et al, 2014;Riffel et al, 2016), Fe-oxide grain size and crystallite size (Shuster et al, 2005), or mixture of Fe-oxides of different ages (Heller et al, 2022). To avoid U, Th, or Sm loss, the heating phase was carefully undertaken to degas all He content, and temperature was regularly monitored.…”

Section: Discussion (U-th)/he Age Significancementioning

confidence: 99%

“…Additionally, the variability in U, Th, and age found in aliquots from the same subsample can result from different generations of Fe-oxides, or simply different Fe-oxides, that developed tightly and are highlighted in SEM observations by a difference in contrast and texture (Figures 3F, 5A,C,F,G,I) (Monteiro et al, 2014;Heller et al, 2022).…”

Section: Discussion (U-th)/he Age Significancementioning

confidence: 99%

“…The present-day climate of the study area is classified as tropical rainforest climate (Af) in the Köppen climate classification, with a FIGURE 1 | (A) Simplified geological map of the Guiana shield (data from geosgb. cprm.gov.br) with location of dated laterites with 40Ar/39Ar, (U-Th)/He, EPR, or paleomagnetism on the Amazon craton (Vasconcelos et al, 1994;Théveniaut and Freyssinet, 2002;Balan et al, 2005;Allard et al, 2018;Heller et al, 2022) and (B) elevation map with known bauxite deposits in Suriname.…”

Section: Geological and Environmental Settingsmentioning

confidence: 99%

“…The dynamics of duricrust formation is still debated, especially in remote places, and requires further geochronological investigations of the different minerals forming the duricrust. High-resolution geochronological tools allow us to determine the different coexisting generations of the same mineral and to constrain the formation and evolution of weathering surfaces, for example, 40 Ar/ 39 Ar on K-bearing minerals (Vasconcelos et al, 1994;Ruffet et al, 1996;Hénocque et al, 1998;Carmo and Vasconcelos, 2006;Beauvais et al, 2008;Riffel et al, 2015;Deng et al, 2016), (U-Th)/He dating on Fe-oxides (Shuster et al, 2005;Heim et al, 2006;Danišík et al, 2013;Monteiro et al, 2014;Riffel et al, 2016;Allard et al, 2018;Wells et al, 2019;Anand et al, 2021;Heller et al, 2022), or electron paramagnetic resonance (EPR) on kaolinite (Balan et al, 2005;Allard et al, 2018). Iron oxide, a mineral ubiquitous in lateritic profiles, has proven its usefulness in the study of weathering episodes at the scale of a regolith (Shuster et al, 2005;Bernal et al, 2006;Monteiro et al, 2014;Riffel et al, 2016;Allard et al, 2018), which explains why the (U-Th)/He dating methods are widely used for laterite material.…”

Section: Introductionmentioning

confidence: 99%

“…Little is known about the timing of laterite and bauxite formation in this area because only rare paleomagnetic dating and palynological and sedimentary constraints exist (van der Hammen and Wymstra, 1964;Wong, 1986;Wong, 1994;van der Hammen and Hooghiemstra, 2000;Théveniaut and Freyssinet, 2002). Little absolute dating was performed on laterite from northeastern French Guiana (Heller et al, 2022) and the Northern Amazon basin (Allard et al, 2018(Allard et al, , 2020Mathian et al, 2020), while the geochronology of laterites and bauxites from south and central Amazonia and the Brazilian shield is more documented (Vasconcelos et al, 1994;Ruffet et al, 1996;Théveniaut and Freyssinet, 2002;Shuster et al, 2005;Monteiro et al, 2018;Albuquerque et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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(U-Th)/He Geochronology Constraints on Lateritic Duricrust Formation on the Guiana Shield

et al. 2022

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Thick regoliths developed under tropical climate, namely, laterites, resulting from long-term and pronounced geochemical and mineralogical rearrangement of the parent rock in response to environmental changes. Little information is available on the timing of laterite and bauxite formations, especially on the chronology of the main weathering episodes responsible for lateritic cover formation on the Guiana shield. For this purpose, we focused on both lateritic and bauxitic duricrusts developed over the Paleoproterozoic Greenstone Belt in the Brownsberg, Suriname. The duricrust samples have a relatively simple mineralogy (i.e., goethite, gibbsite, hematite, and kaolinite) but reveal, when observed at a microscopic scale, a complex history of formation with multiple episodes of dissolution/reprecipitation. The (U-Th)/He dating of 179 Fe-oxides subsamples shows that duricrusts sampled at the top of the Brownsberg plateau have ages ranging from <0.8 Ma to ∼19 Ma. In contrast, Fe-oxides extracted from detrital duricrust boulders collected downslope indicate formation ages up to 36 Ma. This age discrepancy may indicate that a main episode of physical erosion affected this region between ca. 30 and 20 Ma. Consistently, the bauxite sampled at the mountaintop indicates a younger phase of formation, with Fe-oxides recementing fragments of a preexisting bauxitic material older than ∼15 Ma. Geochronological data also reveal a long-lasting weathering history until the present day, with multiple generations of Fe-oxides in the bauxite and the duricrusts resulting from successive cycles of dissolution and reprecipitation of Fe-oxides associated with redox cycles. This long-lasting weathering history led to geochemical remobilization and apparent enrichment in some relatively immobile elements, such as REE, aluminum, and vanadium, especially in the duricrust sampled at the mountaintop. Our geochronological, mineralogical, and geochemical study of Fe- and Al-crusts from the Brownsberg mountain provide constraints on the evolution of environmental conditions prevailing since the early Oligocene in Suriname.

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Section: Discussion (U-th)/he Age Significancementioning

confidence: 99%

Section: Discussion (U-th)/he Age Significancementioning

confidence: 99%

Section: Geological and Environmental Settingsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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(U-Th)/He Geochronology Constraints on Lateritic Duricrust Formation on the Guiana Shield

et al. 2022

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(U‐Th‐(Sm))/He Thermochronometry and Chronometry

GAUTHERON,

BRICHAU,

PIK

et al. 2024

Fission‐track Thermochronology

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A new model of bauxitization in quartzitic landscapes: A case study from the Southern Espinhaço Range (Brazil)

Campos

Monteiro

Vasconcelos

et al. 2023

Earth Surf Processes Landf

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Lithology plays a fundamental role in rock weathering and erosion, and in landscape evolution. When weathering‐ and erosion‐prone lithologies are protected from erosion by more resilient rock types (e.g., quartzites and banded iron formations) unusual weathering products result. At the Southern Espinhaço Range, Minas Gerais, Brazil, bauxitic weathering profiles are found in a unique geomorphological–lithological–climatic setting. Resistant quartzites acted as a barrier against erosion of interbedded hematite‐phyllite lenses, channelling solution flows and facilitating the formation of deep weathering profiles. The long‐term exposure of the hematite‐phyllites under alternating wet and dry tropical climates favoured widespread bauxitization. Here we investigate the geochemical, mineralogical, geochronological and micromorphological signatures of scaffolded bauxites in order to reconstruct their evolutionary history. Our data suggest that recurrent aluminium and iron mobilization within the profiles were mainly driven by mineral dissolution‐reprecipitation mediated by bioturbation and the influx of vegetation‐derived organic species. (U–Th)/He geochronology of Al‐goethite reveals that bauxitization started at least since the Lower Miocene, with important intensification of weathering in the Upper Miocene and Lower Pleistocene. The adjacent resilient quartzites acted as scaffolds for bauxitization and supported the preservation of more erodible weathering profiles developed over phyllites. Surface waters that could not infiltrate into the impermeable adjacent quartzites preferentially infiltrated into the more weathereable phyllites, enhancing their porosity and permeability, further enhancing weathering. The evolutionary history of Southern Espinhaço Range bauxites suggests a new model of bauxitization in ancient land surfaces evolution underlain by quartzites, where erosion‐prone lithologies are scaffolded by resilient quartzites and survive long‐term weathering with minimum erosion, producing bauxites.

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Reading the climate signals hidden in bauxite

Cited by 19 publications

References 87 publications

(U-Th)/He Geochronology Constraints on Lateritic Duricrust Formation on the Guiana Shield

(U-Th)/He Geochronology Constraints on Lateritic Duricrust Formation on the Guiana Shield

(U‐Th‐(Sm))/He Thermochronometry and Chronometry

A new model of bauxitization in quartzitic landscapes: A case study from the Southern Espinhaço Range (Brazil)

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