Short-lived U and Th isotope distribution in a tropical laterite derived from granite (Pitinga river basin, Amazonia, Brazil): Application to assessment of weathering rate

Mathieu, Daniel; Bernat, M.; Nahon, Daniel

doi:10.1016/0012-821x(95)00199-m

Cited by 90 publications

(37 citation statements)

References 12 publications

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“…Although they are very resistant, after extreme weathering, monazite and thorite end up being dissolved and Th then precipitates as thorianite. Thorium, which had the highest enrichment factor (2.0) is probably the most immobile of all chemical elements, even less immobile than Ti (Mathieu et al, 1995). Niobium occurs as a substituent in very resistant minerals as it replaces Zr in zircon (Muggler, 1998) and Ti in rutile, TiO 2 (Deer et al, 1985).…”

Section: Geochemistry Of Elements That Are Accumulated During Weatheringmentioning

confidence: 97%

Trace element geochemistry in Brazilian Cerrado soils

et al. 2004

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Section: Geochemistry Of Elements That Are Accumulated During Weatheringmentioning

confidence: 97%

Trace element geochemistry in Brazilian Cerrado soils

et al. 2004

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“…However, fully closed systems are not likely to occur according to geochemical studies of U and Th isotopes in various laterites, including specifically nodular zones (see e.g. Chabaux et al, 2003;Dequincey et al, 1999;Mathieu et al, 1995). Accordingly, gamma-ray spectrometry showed disequilibria within U decay chain in nodules from a laterite in central Amazonia (Balan et al, 2005).…”

Section: Kaolinite Epr Agesmentioning

confidence: 99%

Combined dating of goethites and kaolinites from ferruginous duricrusts. Deciphering the Late Neogene erosion history of Central Amazonia

et al. 2018

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This study focuses on the dating of millimetric pisoliths from ferruginous duricrusts located in central Amazonia (Brazil), by coupling detailed mineralogy and two relevant dating methods: (i) (U-Th)/He analysis of goethites by mass spectrometry; (ii) analysis of radiation-induced defects of kaolinites embedded in duricrusts by electron paramagnetic resonance spectroscopy (EPR). Three samples collected at different elevations in the landscape were selected. The goethite corrected ages range from 1.1-15.2 Ma and consistently increase with elevation. EPR was performed on kaolinites after several cycles of a deferration procedure. Considering extreme geochemical scenarii, the ages of kaolinites are 1.7-7.1 Ma for a closed system and 4.0-16.7 Ma for an open system with 100% Rn loss. Ages of goethites and kaolinites are close, in the limit of the uncertainty of the methods. They show important periods of duricrust formation at Middle Miocene and at Late Miocene/Pliocene. Data allow the estimation of lowering rates between 3 and 8 m/Ma, in agreement with independent data available in the literature for the central Amazonia region or even for erosion of other cratons in the world. The two dating methods can be compared on common duricrust samples. By revealing single or multi-step weathering/erosion episodes related to relictual paleosurfaces, they also bring promising contributions to an advanced knowledge of ancient and complex lateritic geosystems.

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“…U-series isotopes in weathering profiles: their abundance varies with time as a function of radioactive decay, loss through mineral dissolution and gain through either illuviation, dust deposition or both. Dosseto et al (2008Dosseto et al ( , 2011Dosseto et al ( , 2012, Ma et al (2010), Mathieu et al (1995), etc.…”

Section: Techniques For the Determination Of Soil Formation Ratesmentioning

confidence: 99%

Soil formation rates on silicate parent material in alpine environments: Different approaches–different results?

2014

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High-mountain soils develop in particularly sensitive environments. Consequently, deciphering and predicting what drives the rates of soil formation in such environments are a major challenge. In terms of soil production or formation from chemical weathering, the predominating perception for highmountain soils and cold environments is often that the chemical weathering 'portion' of soil development is temperature-inhibited, often to the point of non-occurrence. Several concepts exist to determine longterm rates of soil formation and development. We present three different approaches: (1) quantification of soil formation from minimally eroded soils of known age using chronosequences (known surface age and soil thickness -SAST), (2) determination of soil residence times (SRT) and production rates through chemical weathering using (un)stable isotopes (e.g. 230Th/234U activity ratios), and (3) a steady state approach using cosmogenic isotopes (e.g. 10Be). For each method, data from different climate zones, and particularly from high-mountains (alpine environment), are compared. The SAST and steady state approach give quite similar results for alpine environments (European Alps and the Wind River Range (Rocky Mountains, USA)). Using the SRT approach, soil formation rates in mountain areas (but having a temperate climate) do not differ greatly from the SAST and steady state approaches. Independent of the chosen approach, the results seem moderately comparable. Soil formation rates in high-mountain areas (alpine climate) range from very low to extremely high values and show a clear decreasing tendency with time. Very young soils have up to 3-4 orders of magnitude higher rates of development than old soils (105 to 106 yr). This apparently is a result of kinetic limits on weathering in regions having young surfaces and supply limits to weathering on old surfaces. Due to the requirement for chemical weathering to occur, soil production rates cannot be infinitely high. Consequently, a speed limit must exist. In the literature, this limit has been set at about 320 to 450 t/km2/a. Our results from the SAST approach show, however, that in alpine areas soil formation easily reaches rates of up to 800-2000 t/km2/a. These data are consistent with previous studies in mountain regions demonstrating that particularly young soils intensively weather, even under continuous seasonal snowpack and, thus, that the concept of 'temperature-controlled' soil development (soil-forming intervals) in alpine regions must be reconsidered. High-mountain soils develop in particularly sensitive environments. Consequently, deciphering and predicting what drives the rates of soil formation in such environments are a major challenge. In terms of soil production or formation from chemical weathering, the predominating perception for high-mountain soils and cold environments is often that the chemical weathering 'portion' of soil development is temperature-inhibited, often to the point of non-occurrence. Several concepts exist to determine long...

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Short-lived U and Th isotope distribution in a tropical laterite derived from granite (Pitinga river basin, Amazonia, Brazil): Application to assessment of weathering rate

Cited by 90 publications

References 12 publications

Trace element geochemistry in Brazilian Cerrado soils

Trace element geochemistry in Brazilian Cerrado soils

Combined dating of goethites and kaolinites from ferruginous duricrusts. Deciphering the Late Neogene erosion history of Central Amazonia

Soil formation rates on silicate parent material in alpine environments: Different approaches–different results?

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