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| Registros recuperados: 17 | |
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| Oliveira,Marisa T.G. de; Furtado,Sandra M.A.; Formoso,Milton L.L.; Eggleton,Richard A.; Dani,Norberto. |
| Kaolin at Campo Alegre Basin, Santa Catarina State, Brazil was formed from alteration of volcanic acid rocks. Halloysite clays dominate the clay fraction of the matrix of the kaolin body, whereas a poorly crystalline kaolinite is abundant in veins. Some primary blocky structures have high amounts of illite, in one mine, but in general, only low contents of illite-smectite, illite, chlorite-vermiculite, vermiculite and quartz were identified in the clay fraction of the samples. Toward the top of the mines, hematite and lepidocrocite appear in horizontal red and ochre colored levels and the amount of kaolinite increases compared to halloysite. The vertical zoning of alteration levels, the changes in mineralogy, the positive correlation between depth and... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Kaolinite; Halloysite; Halloysite morphology; Kaolin; Weathering; Clay genesis. |
| Ano: 2007 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000400008 |
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| Fontorbe, Guillaume; Frings, Patrick J.; De La Rocha, Christina L.; Hendry, Katharine R.; Conley, Daniel J.. |
| The Paleocene‐Eocene Thermal Maximum (PETM, ca. 56 Ma) is marked by a negative carbon isotope excursion (CIE) and increased global temperatures. The CIE is thought to result from the release of 13C‐depleted carbon, although the source(s) of carbon and triggers for its release, its rate of release, and the mechanisms by which the Earth system recovered are all debated. Many of the proposed mechanisms for the onset and recovery phases of the PETM make testable predictions about the marine silica cycle, making silicon isotope records a promising tool to address open questions about the PETM. We analyzed silicon isotope ratios (δ30Si) in radiolarian tests and sponge spicules from the Western North Atlantic (ODP Site 1051) across the PETM. Radiolarian δ30Si... |
| Tipo: Text |
Palavras-chave: Paleocene‐Eocene Thermal Maximum; Silicon biogeochemical cycle; Silicon isotopes; Weathering. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00627/73939/73287.pdf |
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| Molliex, S.; Jouet, Gwenael; Freslon, Nicolas; Bourles, D. L.; Authemayou, C.; Moreau, Julien; Rabineau, Marina. |
| The Mediterranean domain is characterized by a specific climate resulting from the close interplay between atmospheric and marine processes and strongly differentiated regional topographies. Corsica Island, a mountainous area located in the western part of the Mediterranean Sea is particularly suitable to quantify regional denudation rates in the framework of a source-to-sink approach. Indeed, fluvial sedimentation in East-Corsica margin is almost exclusively limited to its alluvial plain and offshore domain and its basement is mainly constituted of quartz-rich crystalline rocks allowing cosmogenic nuclide Be-10 measurements. In this paper, Holocene denudation rates of catchments from the eastern part of the island of Corsica are quantified relying on in... |
| Tipo: Text |
Palavras-chave: Be-10-derived denudation rates; Schmidt Hammer; Quaternary; Quantitative geomorphology; Weathering. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00380/49082/49655.pdf |
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| Goydaragh,Maryam Ghebleh; Jafarzadeh,Ali Asghar; Shahbazi,Farzin; Oustan,Shahin; Taghizadeh-Mehrjardi,Ruhollah; Lado,Marcos. |
| ABSTRACT Characterizing the elemental composition provides useful information about the weathering degree of soils. In Miandoab County, Northern Iran, this characterization was missing, and thus the objectives of this work were to evaluate the weathering degrees for the most typical soils in the area from their elemental compositions, and to estimate this elemental composition using Fourier transform infrared spectroscopy and Random Forest models. Five soil profiles, including Aridisols and Inceptisols, were selected as the most representative of the area. Major elemental oxides were determined in each genetic horizon by X-ray fluorescence, showing that these soils were at early developmental stages. Only Al2O3 and CaO were accurately estimated, with R2... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: FTIR spectra; Random forest; Weathering. |
| Ano: 2019 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-43662019000600460 |
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| Santos,Roseclênia Alves; Sermarini,Renata Alcarde; Guerra,Adriano Ribeiro; Santos,Jean Cheyson Barros dos; Azevedo,Antonio Carlos de. |
| ABSTRACT Saprolite plays a central role into hydrologic and nutrient cycles. Despite that, saprolite research is scattered and uses heterogeneous, sometimes conflicting, methods and concepts. During field work, it is difficult to assign the boundary between soil and saprolite. This paper aimed to identify the subjacent logic that pedologists use to assign to a regolith volume its soil or saprolite nature. To achieve this goal, a tree algorithm was used to build a hierarchy of physical and chemical properties of a set of regolith profiles. Such hierarchization expose the inner, subjective criteria used by researchers during the assignment of a certain profile zone as saprolite or soil. The following variables were measured: total porosity (TP); bulk density... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Regolite; Subsolum; Weathering; Classification system. |
| Ano: 2019 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832019000100302 |
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| Baronas, J. Jotautas; Torres, Mark A.; West, A. Joshua; Rouxel, Olivier; Georg, Bastian; Bouchez, Julien; Gaillardet, Jerome; Hammond, Douglas E.. |
| Solutes derived from the dissolution of silicate minerals play a key role in Earth’s climate via the carbon and other biogeochemical cycles. Silicon (Si) is a unique constituent of silicate minerals and a biologically important nutrient, so tracing its behavior in near-surface environments may provide important insights into weathering processes. However, Si released by weathering is variably incorporated into secondary mineral phases and biota, obscuring signals derived from primary weathering processes. Due to chemical similarities, Germanium (Ge) may help better understand the Si cycle and its relationship to chemical weathering. With this aim, we report new measurements of the concentration and isotopic composition of Ge for both the dissolved and... |
| Tipo: Text |
Palavras-chave: Germanium; Silicon; Isotopes; Rivers; Weathering; Fractionation. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00460/57196/59370.pdf |
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| Escoube, Raphaelle; Rouxel, Olivier; Pokrovsky, Oleg S.; Schroth, Andrew; Holmes, Robert Max; Donard, Olivier F. X.. |
| The input of iron to the Arctic Ocean plays a critical role in the productivity of aquatic ecosystems and is potentially impacted by climate change. We examine Fe isotope systematics of dissolved and colloidal Fe from several Arctic and sub-Arctic rivers in northern Eurasia and Alaska. We demonstrate that the Fe isotopic (δ56Fe) composition of large rivers, such as the Ob’ and Lena, has a restricted range of δ56Fe values ca.–0.11 ± 0.13‰, with minimal seasonal variability, in stark contrast to smaller organic-rich rivers with an overall δ56Fe range from–1.7 to + 1.6‰. The preferential enrichment with heavy Fe isotopes observed in low molecular weight colloidal fraction and during the high-flow period is consistent with the role of organic complexation of... |
| Tipo: Text |
Palavras-chave: Iron isotope; Colloids; River; Weathering; Arctic; Iron speciation. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00273/38402/36865.pdf |
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| Ratie, G.; Garnier, J.; Calmels, D.; Vantelon, D.; Guimaraes, E.; Monvoisin, G.; Nouet, J.; Ponzevera, Emmanuel; Quantin, C.. |
| Ultramafic (UM) rocks are known to be nickel (Ni) rich and to weather quickly, which makes them a good candidate to look at the Ni isotope systematics during weathering processes at the Earth’s surface. The present study aims at identifying the Ni solid speciation and discussing the weathering processes that produce Ni isotope fractionation in two deep laterite profiles under tropical conditions (Barro Alto, Goiás State, Brazil). While phyllosilicates and to a lower extent goethite are the main Ni-bearing phases in the saprolitic part of the profile, iron (Fe) oxides dominate the Ni budget in the lateritic unit. Nickel isotopic composition (δ60Ni values) has been measured in each unit of the regolith, i.e., rock, saprock, saprolite and laterite (n=52).... |
| Tipo: Text |
Palavras-chave: Nickel cycle; Lateritic regolith; Nickel isotopes; XANES; Ultramafic environment; Weathering. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00436/54712/56149.pdf |
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| Ratie, G.; Jouvin, D.; Garnier, Julien; Rouxel, Olivier; Miska, S.; Guimaraes, E.; Cruz Vieira, L.; Sivry, Y.; Zelano, I.; Montarges-pelletier, E.; Thil, F.; Quantin, C.. |
| Although Ni isotopes have been shown to be significantly fractionated in terrestrial samples, their use in continental environmental studies has not yet been evaluated. The present study focuses on an ultramafic (UM) massif (Barro Alto, Goias, Brazil) because such areas are naturally rich in Ni. We present developed lateritic weathering profiles. The goal of the study is to evaluate the potential of using Ni isotopes in environmental continental studies by combining its isotopic signature with mineralogy, in order to better understand the geochemical cycling of Ni in UM settings during weathering. As such, Ni isotope values were measured in samples from the Barro Alto UM complex in the main stages of the lateritic weathering profile of UM rocks, including... |
| Tipo: Text |
Palavras-chave: Nickel; Isotope; Weathering; Mineralogy; Soil. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00254/36553/35098.pdf |
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| Ferreira,José Thales Pantaleão; Ribeiro Filho,Mateus Rosas; Ribeiro,Mateus Rosas; Souza Júnior,Valdomiro Severino de; Bittar,Sheila Maria Bretas; Santos,Robson Gomes dos. |
| ABSTRACT The semiarid region of northeastern Brazil has a large area occupied by Planosols, where in the State of Pernambuco these soils are mainly used for livestock farming and subsistence crops. The knowledge on these soils is limited, which compromises the understanding on their behavior, potentialities and limitations.This study aimed to analyze morphological, chemical, physical and mineralogical attributes of Planosols developed under different geoenvironmental conditions. Morphological descriptions and chemical, physical and mineralogical analyses were performed in four profiles of Planosols along a rainfall gradient. An increase in rainfall allowed for an increase in the clay content in the Bt horizon and a reduction in ESP, EC, Na+, CEC, S, pH... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Soil mineralogy; Weathering; Climate; Semiarid. |
| Ano: 2016 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832016000100302 |
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| Ferreira,Edilene Pereira; Guerra,Adriano Ribeiro; Azevedo,Antonio Carlos de. |
| ABSTRACT: Regolith characterization in its entirety is particularly difficult in gneissic regoliths due to the heterogeneity of their rock structure. Rare earth elements (REE) are a useful tool in helping understand the evolution of regoliths. This study relates the mineralogy and weathering indexes of three gneisses regoliths (P1-leucocratic, P2-mesocratic and P3-melanocratic gneisses) to the distribution of REE at depth. In soil, clay activity, iron and manganese oxides, CaO, SiO2, P2O5, TiO2, Fe2O3, and MgO showed high positive correlation with REE. The absolute content of REE was enriched in mafic minerals. At the interface between the soil and saprolite, the sum of absolute REE content was greater in soil than in saprolite in P1, while the opposite... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Saprolite; Weathering; Pedogenesis. |
| Ano: 2021 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162021000301404 |
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| SÁNCHEZ,Liz Stefanny Hidalgo; HORBE,Adriana Maria Coimbra; MOQUET,Jean-Sébastien; SONDAG,Francis; GUYOT,Jean-Loup. |
| The Amazon River basin is important in the contribution of dissolved material to oceans (4% worldwide). The aim of this work was to study the spatial and the temporal variability of dissolved inorganic materials in the main rivers of the Amazon basin. Data from 2003 to 2011 from six gauging stations of the ORE-HYBAM localized in Solimões, Purus, Madeira and Amazon rivers were used for this study. The concentrations of Ca2+, Na+, K+, Mg2+, Cl-, SO4 -2, HCO3 - and SiO2 were analyzed. At the stations of Solimões and Amazon rivers, the concentrations of Ca2+, Mg2+, HCO3 - and SO4 -2 had heterogeneous distribution over the years and did not show seasonality. At the stations of Madeira river, the concentration of these ions had seasonality inversely proportional... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Weathering; Hydrochemistry fluxes; Theoretical dilution; Hydroclimatology. |
| Ano: 2015 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0044-59672015000200175 |
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| Revillon, Sidonie; Jouet, Gwenael; Bayon, Germain; Rabineau, Marina; Dennielou, Bernard; Hemond, Christophe; Berne, Serge. |
| In this study, we undertook a reconnaissance study of sediments provenance in the Gulf of Lions focusing over the last 16 ka. We used geochemical and isotopic tracers to determine the source of sediments and give insight into the weathering conditions prevailing. Sediments samples were selected both onshore and offshore from the western, eastern, and central part of the Gulf of Lions. We analyzed bulk sediments, coarse and fine silt, and clay fractions. Elemental and Nd isotope compositions appeared to differ from one grain size fraction to another one. These are interpreted in terms of zircon addition in the coarse silt fraction for the elemental concentrations and variable sources influences for the Nd isotope compositions. Our results indicate that... |
| Tipo: Text |
Palavras-chave: Geochemistry; Provenance; Sediment; Weathering. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00043/15376/12734.pdf |
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| Bayon, Germain; Delvigne, C.; Ponzevera, Emmanuel; Borges, A. V.; Darchambeau, F.; De Deckker, P.; Lambert, T.; Monin, L.; Toucanne, Samuel; Andre, L.. |
| The δ30Si stable isotopic composition of silicon in soils and fine-grained sediments can provide insights into weathering processes on continents, with important implications on the Si budget of modern and past oceans. To further constrain the factors controlling the distribution of Si isotopes in sediments, we have analysed a large number (n=50) of separate size-fractions of sediments and suspended particulate materials collected near the mouth of rivers worldwide. This includes some of the world’s largest rivers (e.g. Amazon, Congo, Mackenzie, Mississippi, Murray-Darling, Nile, Yangtze) and rivers from the case study areas of the Congo River Basin and Northern Ireland. Silt-size fractions exhibit a mean Si isotopic composition (δ30Si = -0.21 ± 0.19‰; 2... |
| Tipo: Text |
Palavras-chave: World rivers; Congo basin; Northern Ireland; Si isotopes; Clay minerals; Weathering; Temperature; Precipitation. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00434/54609/55991.pdf |
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| Registros recuperados: 17 | |
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