Accedi

Bibliografie tematiche / Duricrust / Articoli di riviste

Segui questo link per vedere altri tipi di pubblicazioni sul tema: Duricrust.

Articoli di riviste sul tema "Duricrust"

Autore: Grafiati

Pubblicato: 22 febbraio 2025

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili

Scegli il tipo di fonte:

Vedi i top-50 articoli di riviste per l'attività di ricerca sul tema "Duricrust".

Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.

Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.

Vedi gli articoli di riviste di molte aree scientifiche e compila una bibliografia corretta.

1

DE TOLEDO, MARIA CRISTINA MOTTA, SONIA BARROS DE OLIVEIRA, MARCONDES LIMA DA COSTA, CAMILA PASSOS e HENRIQUE DINIZ DE ALMEIDA. "Evolução do Manto de Intemperismo Laterítico Rico em Fosfatos na Ilha de Itacupim (PA) - Mineralogia, Micromorfologia e Geoquímica". Pesquisas em Geociências 33, n. 2 (29 giugno 2006): 109. http://dx.doi.org/10.22456/1807-9806.19520.

Testo completo

Abstract (sommario):

The lateritic mantle overlying ultramafic rocks at Itacupim Island (state of Pará, northern Brazil) comprises 5 horizons. From bottom to top they are: (1) altered rock (hornblende, phlogopite, apatite, magnetite, fissural wavellite, and smaller amounts of smectite or kaolinite), (2) a smectitic saprolite (smectite, wavellite, goethite, and traces of hornblende), a kaolinitic saprolite (kaolinite, wavellite, goethite, and traces of phlogopite), a phosphatic duricrust (crandallite, goethite and hematite), and a ferruginous duricrust (hematite, goethite and crandallite). The mineralogical and chemical composition of the saprolitic and duricrust horizons indicate a discontinuity in the weathering evolution: the P-rich crandallitic duricrusts cannot be derived from the P-poor wavellitic saprolites. Most probably, the duricrusts developed during an earlier stage of the weathering evolution, under a drier climate, when the hypogene phosphates (wavellite and apatite) transformed into crandallite. Under subsequent more humid conditions, the weathering alteration of the parent rock led to the dissolution of the hypogene phosphates, resulting in the P-depleted saprolites.

Gli stili APA, Harvard, Vancouver, ISO e altri

2

Fenske, Caroline, Jean Braun, François Guillocheau e Cécile Robin. "A numerical model for duricrust formation by water table fluctuations". Earth Surface Dynamics 13, n. 1 (3 febbraio 2025): 119–46. https://doi.org/10.5194/esurf-13-119-2025.

Testo completo

Abstract (sommario):

Abstract. Duricrusts are hard mineral layers forming in climatically contrasted environments. They form in tropical to arid environments and can be currently observed all around the world in areas such as Europe, Africa, South America, India, and Australia. In most cases, they cap hills and appear to protect softer layers beneath. Two main hypotheses have been proposed for the formation of duricrusts; i.e. the hydrological or transported model, where the enrichment in the hardening element (iron for ferricretes, silica for silcretes, or calcium carbonates for calcretes) is the product of leaching and precipitation through fluctuations in the water table during contrasted seasonal cycles, and the laterization or in situ model, where the formation of duricrusts is the final compacting stage of laterization. In this article, we present the first numerical geomorphological model for the formation of duricrusts based on the hydrological hypothesis. The model is an extension to an existing regolith formation model, where the position of the water table is used to predict the formation of a hardened layer at a rate set by a characteristic timescale, τ, and over a depth set by the range of fluctuations in the water table, λ. Hardening causes a decrease in surface erodibility, which we introduce in the model as a dimensionless factor, κ, that multiplies the surface transport coefficient of the model. Using the model, we show under which circumstances duricrusts form by introducing two dimensionless numbers that combine the model parameters (λ and τ), as well as parameters representing external forcing like precipitation rate and uplift rate. We demonstrate that when using model parameter values obtained by independent constraints from field observations, hydrology, and geochronology, the model predictions reproduce the observed conditions for duricrust formation. We also show that a strong feedback exists due to duricrust formation on the shape of the regolith and the position of the water table. Finally, we demonstrate that although duricrusts protect elements of the landscape, their efficiency in doing so is significantly lower than their inherent strength.

Gli stili APA, Harvard, Vancouver, ISO e altri

3

Seralathan, P., e D. Padmalal. "Geochemistry of the Tertiary Formation at Pozhikkara Cliff Section, Kerala-Its Palaeoenvironmental Significance". Journal Geological Society of India 38, n. 3 (1 settembre 1991): 277–81. http://dx.doi.org/10.17491/jgsi/1991/380304.

Testo completo

Abstract (sommario):

Abstract The Tertiary sequence begins with fossiliferous marl and is overlain by carbonaceous clay, china clay and laterite. The thin (3 cm thick), hard, compact duricrust layer, which is found interbedded within the carbonaceous clays, shows abnormal geochemical anomalies. Major elements such as Fe, Mn and Ca and the trace element Co show about 2-3 fold and 1-2 fold increase respectively in the duricrust than the upper and lower sections. However, the content of Na, K, Ni, Cu and organic carbon show an opposite trend. Cd does not show any marked variation along the profile. The CaCO3 content is remarkably high in the duricrust and marl than the other layers. Fe and Mn contents are much higher in the laterite than china clay, other parameters do not show much variation. The high content of Fe, Mn, Ca and CaCO3 and low Ni/Co ratio and organic carbon content in the duricrust layer indicate an oxidizing environmental condition which existed at the time of the formation of this layer, while the converse trend of these parameters in the carbonaceous clays indicate the prevalence of a reducing condition.

Gli stili APA, Harvard, Vancouver, ISO e altri

4

Freitas, Caroline Araujo, Adriana Maria Coimbra Horbe, Márcio Fernando dos Santos Albuquerque e Rodrigo Tokuta Castro. "Unraveling Parent Rock and Mineral Influences in Tropical Weathering Profiles: REE, Nd and Sr Isotopic Geochemistry". Minerals 14, n. 5 (28 aprile 2024): 470. http://dx.doi.org/10.3390/min14050470.

Testo completo

Abstract (sommario):

This study aims to investigate the effects of parent rock and minerals on lateritic weathering. The study presents X-ray diffraction (XRD), whole-rock geochemistry, and Nd-Sr isotopic data for examining two profiles, 10 and 12 m thick, respectively, that illustrate the regional tropical weathering status in the Midwest of Brazil. The profiles, developed from metasedimentary and sedimentary rocks, are constituted by saprolite, mottled horizon, lateritic duricrust, and oxisol. Across the profiles, the minerals controlling the weathering geochemistry are muscovite, microcline, quartz, kaolinite, hematite, goethite, and gibbsite. Red and yellow zones in the saprolite and mottled horizon as well as the lateritic duricrust with breccia/fragmental, pisolitic, and oolitic textures make profile 1 more complex. In contrast, profile 2 has an oxisol that mantles the homogeneous vermiform lateritic duricrust. Fe2O3, accumulated during surface weathering, is a potent element in the geochemical profile control since it forms the harder goethite to hematite lateritic duricrust, bearing most of the trace elements (As, Cu, Cs, Pb, Sc, Sr, Th, U, V, and Zn) with similar ionic radii and electrovalence. The LREE have affinity for the elements of the Fe2O3 group of the lateritic duricrust. On the other hand, the K2O group together with Zr and TiO2 e in the phyllite, saprolite, and mottled horizon of profile 1, are associated with the HREE. Additionally, in profile 2, the HREE are mostly associated with the Al2O3 group and the residual minerals in the oxisol. The indication that REE is associated with phosphates, zircon, rutile/anatase, cereanite, and muscovite/illite, which have variable weathering behavior, caused the REE fractionation to occur across and between the profiles. Despite the REE fractionation, the ƐNd(0) values along the profiles consistently maintain the signature of the parent rock. Muscovite and microcline weathering, in profiles 1 and 2, respectively, control the decrease in 87Sr/86Sr signatures of both profiles and the distinct radiogenic ratios. The development of lateritic duricrust in both profiles indicates a similar weathering intensity, although the gibbsite–kaolinite predominance in the oxisol of profile 2 highlights a geochemical reorganization under humid conditions, as well as near-intense soluble silica leaching.

Gli stili APA, Harvard, Vancouver, ISO e altri

5

Anand, RR, e RJ Gilkes. "Variations in the properties of iron oxides within individual specimens of lateritic duricrust". Soil Research 25, n. 3 (1987): 287. http://dx.doi.org/10.1071/sr9870287.

Testo completo

Abstract (sommario):

The morphologically distinct materials in Darling Range lateritic duricrust (i.e. loose and cemented pisoliths, concretions, matrix, pisolith coatings and void coatings) exhibit goethite/(goethite + hematite) ratios ranging from 0.15 for individual pisoliths to 1.0 for void coatings. Mole % Al substitution ranged from 20 to 34% in goethite and from 2 to 15% in hematite. Goethite and hematite in pisoliths and concretions were mostly highly Al substituted. Al substitution in goethite was positively related (P < 0.01) to Al substitution in hematite. Al substitution in maghemite was less than 5%. Goethite crystals ranged in size from 130 to 260 A. Hematite crystals ranged from 140 to 520 A, and were systematically smaller in pisoliths. Crystal size of goethite and hematite decreased with increasing Al substitution. Hematite crystals were usually about 50% larger than goethite crystals in the same sample, and crystal sizes of goethite and hematite were positively correlated (P < 0.01). Goethite and hematite occurred as aggregates of subrounded platy crystals. Differences in the properties of goethite and hematite between morphologically distinct materials in single hand specimens are indicative of the complex history of these duricrusts.

Gli stili APA, Harvard, Vancouver, ISO e altri

6

Sojien, Taylor Moise, Estelle Lionelle Tamto Mamdem, Armand Sylvain Ludovic Wouatong e Dieudonne Lucien Bitom. "Mineralogical, Geochemical and Distribution Study of Bauxites in the Locality of Bangam and Environs (West Cameroon)". Earth Science Research 7, n. 1 (24 gennaio 2018): 117. http://dx.doi.org/10.5539/esr.v7n1p117.

Testo completo

Abstract (sommario):

The bauxite duricrust in the Bangam and surroundings is classified into three major storey levels as follows: the upper level on top of the plateaus where the continuous bauxites outcrop in slabs over distances of about 1 km, the intermediate level on top and at the flanks of the hills where the bauxites flush in metric blocks, the lower level at the talwegs where bauxites duricrust are gravels. The average thickness of the duricrust is 9.6m and extends over an area of about 9.5km2. Five types of facies are encountered here: nodular, pisolitic, pseudobreccia, vacuolar and massive. These different facies were carried out by X-ray fluorescence spectrometry, X-ray diffractometric, thermal analysis (ATD / ATG) and by polarizing microscope observation. The results of these analyses show that, gibbsite is the dominant mineral; kaolinite, anatase, hematite, goethite, magnetite and ilmenite are also present. The chemical composition of the major elements that characterize bauxites are 38-60% Al2O3; 2 -22% SiO2 and 9-42% Fe2O3. These values are almost similar to those obtained in Doumbouo-Fokoué, Ghana, Ngaoundal, and Minim-Martap precisely at Briskok prospect. The different minerals paragenesis and geochemistry data show that, the Bangam locality is a bauxite ore deposit in spite of a high content of iron and silicate of some facies, nevertheless, these can be used in some industries.

Gli stili APA, Harvard, Vancouver, ISO e altri

7

Taylor, Graham, e Bryan P. Ruxton. "A duricrust catena in South-east Australia". Zeitschrift für Geomorphologie 31, n. 4 (17 dicembre 1987): 385–410. http://dx.doi.org/10.1127/zfg/31/1987/385.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

8

Conacher, A. J. "Lateritic duricrust and relief inversion in Australia". CATENA 18, n. 6 (dicembre 1991): 585–88. http://dx.doi.org/10.1016/0341-8162(91)90041-u.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

9

de Oliveira, S. M. B., e E. G. Campos. "Gold-bearing iron duricrust in Central Brazil". Journal of Geochemical Exploration 41, n. 3 (novembre 1991): 309–23. http://dx.doi.org/10.1016/0375-6742(91)90005-f.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

10

Sousa, D. J. L., A. F. D. C. Varajão, J. Yvon e G. M. Da Costa. "Mineralogical, micromorphological and geochemical evolution of the kaolin facies deposit from the Capim region (northern Brazil)". Clay Minerals 42, n. 1 (marzo 2007): 69–87. http://dx.doi.org/10.1180/claymin.2007.042.1.06.

Testo completo

Abstract (sommario):

AbstractThe Capim Kaolin District (eastern Brazilian Amazon), is one of the largest kaolin deposits in the world; with the kaolin used mainly for paper coating. The kaolin developed at the expense of Cretaceous sandy-clayey sediments of the Ipixuna formation, through intense lateritization from the Mesozoic to Cenozoic times.This work describes the morphological, mineralogical, crystallochemical and geochemical evolution of the Capim kaolin facies. Based on the profile analysis in the open pit fronts, it encompasses X-ray diffraction, thin-section optical analysis, EDS-assisted scanning electron microscopy and transmission electron microscopy, chemical analysis, infrared and Mössbauer spectroscopies.Six facies were defined as different stages of the supergene process. Ferruginization led to a thick duricrust on the soft kaolin, which in turn evolved from sandy-clayey sediments of the Ipixuna Formation. A subsequent deferruginization event degraded the duricrust, resulting in the flint kaolin facies.

Gli stili APA, Harvard, Vancouver, ISO e altri

11

Rodas, M., F. J. Luque, R. Mas e M. G. Garzon. "Calcretes, Palycretes and Silcretes in the Paleogene Detrital Sediments of the Duero and Tajo Basins, Central Spain". Clay Minerals 29, n. 2 (giugno 1994): 273–85. http://dx.doi.org/10.1180/claymin.1994.029.2.13.

Testo completo

Abstract (sommario):

AbstractThree duricrust types (calcretes, palycretes and silcretes) have been distinguished in the Lower Paleogene arkosic materials from the margins of the Duero and Tajo basins (central Spain). In the calcretes the cements are composed of calcite plus palygorskite, whereas palygorskite is the only cement in the palycretes. In the silcretes, the cement consists chiefly of opal and chalcedony, with minor quartz. The important duricrust development in the Paleogene detrital materials can be correlated with a drastic climatic change towards colder and more arid conditions during this time, as inferred from the sedimentological features and the clay mineral evolution. The origin of calcretes and palycretes is related to the movement of alkaline phreatic waters generated from dolomitic rocks of Cretaceous age cropping out in the near surroundings. Silcretes originated from the vertical transfer of silica from supersaturated groundwaters, from the Hercynian granitic rocks, up to the surface. Silcretes are developed either on unconsolidated arkosic materials or replace previous calcrete or palycrete levels.

Gli stili APA, Harvard, Vancouver, ISO e altri

12

Levett, Alan, Emma Gagen, Jeremiah Shuster, Llew Rintoul, Mark Tobin, Jitraporn Vongsvivut, Keith Bambery, Paulo Vasconcelos e Gordon Southam. "Evidence of biogeochemical processes in iron duricrust formation". Journal of South American Earth Sciences 71 (novembre 2016): 131–42. http://dx.doi.org/10.1016/j.jsames.2016.06.016.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

13

Marques, Karina P. P., Thierry Allard, Cécile Gautheron, Benoît Baptiste, Rosella Pinna-Jamme, Guillaume Morin, Ludovic Delbes e Pablo Vidal-Torrado. "Supergene phases from ferruginous duricrusts: non-destructive microsampling and mineralogy prior to (U–Th) ∕ He geochronological analysis". European Journal of Mineralogy 35, n. 3 (14 giugno 2023): 383–95. http://dx.doi.org/10.5194/ejm-35-383-2023.

Testo completo

Abstract (sommario):

Abstract. Interpreting the ages of supergene mineralogical phases in laterite is complex because they consist of polycrystalline mixtures of different phases at the microscopic scale that could be crystalized at different epochs. Among the geochronometers, the (U-Th)/He method on hematite and goethite is more often used, but ages can be difficult to interpret due to phases mixing. To resolve this issue, this study proposes a methodology for performing detailed mineralogical analysis of hematite and goethite single grains prior to their dating using the (U-Th)/He method. Strictly non-destructive mineralogy of single grains is not achievable by classical tools, such as conventional powder XRD (X-ray diffraction; requiring at least some milligrams of powder) or SEM (scanning electron microscopy; that can contaminate the grain by coating or fixing). Therefore, we performed X-ray diffraction patterns of single grains using high-flux X-ray beams from both a rotating anode (XRD_rotat) laboratory diffractometer and a synchrotron beamline (XRD_synch) and compared the results in order to design a method based on XRD_rotat only. For this purpose, two samples from the pisolitic facies of a Brazilian ferruginous duricrust (Alto Paranaíba region, Minas Gerais State, Brazil) were chosen because they presented a usual heterogeneity. Rietveld refinements of the XRD patterns obtained from both XRD_rotat and XRD_synch yielded similar results for the weight percentage ratio of the main phases and mean coherent domain sizes and less similar results for Al substitution rates, thus validating the XRD_rotat approach. No beam damage was observed when increasing X-ray exposure time, neither on XRD patterns nor on (U-Th)/He ages. Hence, sub-millimeter, undisturbed grains can be used to analyze the mineralogy of ferruginous duricrusts by XRD_rotat with a short exposure, and the same grains can subsequently be dated by (U-Th)/He geochronology analysis. The (U-Th)/He dating of pisolitic core and cortex grains also provided meaningful ages: they revealed two evolution phases of the ferruginous duricrust, which occurred at or before the Oligocene for the pisolitic core and middle Miocene for the pisolitic cortex, agreeing with the previous model for the development of pisolites. The mineralogy of single grains selected for dating is helpful for discussing the crystallization ages, and the high-flux XRD approach may be applied to other supergene mineral parageneses used for absolute dating.

Gli stili APA, Harvard, Vancouver, ISO e altri

14

Jakosky, Bruce M., e Philip R. Christensen. "Global duricrust on Mars: Analysis of remote-sensing data". Journal of Geophysical Research: Solid Earth 91, B3 (10 marzo 1986): 3547–59. http://dx.doi.org/10.1029/jb091ib03p03547.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

15

Lewinger, William, Francisco Comin, Marcus Matthews e Chakravarthini Saaj. "Earth analogue testing and analysis of Martian duricrust properties". Acta Astronautica 152 (novembre 2018): 567–79. http://dx.doi.org/10.1016/j.actaastro.2018.05.025.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

16

Brizzi, Raphael Rodrigues, Fernando Nadal Junqueira Villela, Amanda de Fátima Martin Catarucci, Heitor Paiva Palma e Pablo Vidal-Torrado. "RECOGNITION OF DURICRUST GEOMORPHIC SURFACES USING A RELIEF DISSECTION MATRIX". Mercator 23, n. 2024 (28 ottobre 2024): 1–13. http://dx.doi.org/10.4215/rm2024.e23021.

Testo completo

Abstract (sommario):

Landforms can orientate the hydrodynamics and distribution of materials on the ground, producing flattened and/or lowered geomorphic surfaces given the evolutionary characteristics from climatic, morphogenetic and pedogenetic factors. This work aims to demonstrate the compartmentalization and association of geomorphic surfaces covered by ferruginous duricrusts in Savannah areas in Brazil according to a relief dissection matrix. This matrix indicates the vertical cutting of the valleys and the interfluvial horizontal dimension of the hills through landform measurements in radar images, classification in alphanumeric codes and statistical correlations. The results indicated details in the compartmentalization of the surface according to the landform roughness, making it possible to link, through data from the dissection matrix and the statistical correlation, the association between the compartments according to summit positions and remaining depressed areas. Despite the fact that more robust measurements obtained from high-precision mappings can point out further landform evolutionary stages, it is understood that a dissection matrix and its statistical correlations can not only compartmentalize the landscape and provide an initial overview of the landscape’s evolution, but also indicate geomorphic surfaces that could have been worked at the same time. In this sense, the recognition of geomorphic surfaces, occurrence of duricrusts and landforms in this work allowed a certain morphogenetic correspondence that can contribute to geomorphological studies, although the results must be observed with caution when verified from the tropical perspective of relief evolution. Keywords: Valley Cutting; Interfluvial Dimension; Dissection Matrix; Geomorphic Surfaces; Duricrusts

Gli stili APA, Harvard, Vancouver, ISO e altri

17

Varajão, A. F. D. C., G. M. Da Costa, C. A. C. Varajão, J. D. Meunier e F. Colin. "Iron-bearing phases in a peat-derived duricrust from Brazil". European Journal of Soil Science 58, n. 5 (ottobre 2007): 1096–106. http://dx.doi.org/10.1111/j.1365-2389.2007.00891.x.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

18

Khalifa, M. A., Fujio Kumon e Kokhi Yoshida. "Calcareous duricrust, Al Qasim Province, Saudi Arabia: Occurrence and origin". Quaternary International 209, n. 1-2 (novembre 2009): 163–74. http://dx.doi.org/10.1016/j.quaint.2009.02.014.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

19

Anand, RR, e RJ Gilkes. "The association of maghemite and corundum in Darling Range laterites, Western Australia". Soil Research 25, n. 3 (1987): 303. http://dx.doi.org/10.1071/sr9870303.

Testo completo

Abstract (sommario):

Maghemite in Darling Range lateritic duricrust ranges from 2 to 10% in abundance, contains less than 5 mole % Al and occurs as aggregates of very small ~ 150 A subrounded platy crystals. Corundum is also present, ranging from 1 to 3.5% in abundance, and it contains less than 3 mole % Fe and occurs as rounded (~250 A) crystals. The maghemite and corundum contents are positively correlated (P < 0.01), which may indicate a common origin due to dehydroxylation of Fe and Al oxyhydroxides in bush fires.

Gli stili APA, Harvard, Vancouver, ISO e altri

20

Shaw, P. A., e J. J. De Vries. "Duricrust, groundwater and valley development in the Kalahari of southeast Botswana". Journal of Arid Environments 14, n. 3 (maggio 1988): 245–54. http://dx.doi.org/10.1016/s0140-1963(18)31071-1.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

21

Liu, Huan, Xiancai Lu, Juan Li, Xiaoye Chen, Xiangyu Zhu, Wanli Xiang, Rui Zhang, Xiaolin Wang, Jianjun Lu e Rucheng Wang. "Geochemical fates and unusual distribution of arsenic in natural ferromanganese duricrust". Applied Geochemistry 76 (gennaio 2017): 74–87. http://dx.doi.org/10.1016/j.apgeochem.2016.11.012.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

22

Vuleta*, Sophie, Monica LeGras, Raymond E Smith, Carsten Laukamp, Louise Schoneveld e Ravi Anand. "Characterising lithium host minerals within the lateritic duricrust, Greenbushes, Western Australia". ASEG Extended Abstracts 2019, n. 1 (11 novembre 2019): 1–2. http://dx.doi.org/10.1080/22020586.2019.12073086.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

23

Nash, David J., Paul A. Shaw e David S. G. Thomas. "Duricrust development and valley evolution: Process–landform links in the kalahari". Earth Surface Processes and Landforms 19, n. 4 (giugno 1994): 299–317. http://dx.doi.org/10.1002/esp.3290190403.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

24

Messias Martins, Ramon, Angélica Fortes Drummond Chicarino Varajão, Fábio Soares de Oliveira, Thierry Allard, Cesar Augusto Chicarino Varajão e Caroline Delpupo Souza. "Degradation systems of ferruginous duricrust in the Barreiras Formation, Southeastern Brazil". CATENA 246 (novembre 2024): 108463. http://dx.doi.org/10.1016/j.catena.2024.108463.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

25

Iglesias-Martínez, Mario, Berta Ordóñez-Casado e Edgar Berrezueta. "Optical image and microchemical analysis of gold grains from a weathered profile of the Minvoul greenstone belt, northern Gabon". Geological Magazine 157, n. 2 (30 agosto 2019): 307–20. http://dx.doi.org/10.1017/s0016756819000827.

Testo completo

Abstract (sommario):

AbstractMorphological characterization and quantification of gold particles by optical image analysis (OIA) and by compositional analysis of microprobes using scanning electron microscope and electron microprobe analysis techniques were carried out on gold grains from the Minvoul area (Archean greenstone belt in Gabon). Large grains of almost pure gold were found throughout a weathering profile, which consisted of saprolite, mottled clay zone, iron duricrust, pisolitic gravels and yellow latosol. In the deeper horizons, gold was dissolved as shown by corrosion features on the surface of particles with average sizes of 2.6Φ and 2.35Φ in the saprolite and mottled clay zones, respectively. The occurrence of secondary gold in the duricrust was indicated by the larger size of the nuggets (average, 1.8Φ), the high fineness (> 995 in average) and the close textural relationship between gold and neoformed iron oxyhydroxides. The uppermost horizons composed of yellow latosol and pisolitic gravels were interpreted as transported materials based on their size distribution (average 0.85Φ and 1.34Φ), sorting and shape parameters. The best morphological parameter to describe the whole weathering profile was found to be the perimeter/area ratio. The highest ratios were recorded in the saprolite (average 0.192 μm−1), and decreased towards the surface (average 0.057 μm−1). The combination of the OIA technique and the microchemical analysis of gold grains allowed us to define specific morphological and compositional characteristics of the gold particles for each horizon. Both methods proved to be of great utility to understand gold concentration, dissolution and dispersion processes in supergene environments.

Gli stili APA, Harvard, Vancouver, ISO e altri

26

Beauvais, A., e F. Colin. "Formation and transformation processes of iron duricrust systems in tropical humid environment". Chemical Geology 106, n. 1-2 (maggio 1993): 77–101. http://dx.doi.org/10.1016/0009-2541(93)90167-h.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Ringrose, S., L. Cassidy, S. Diskin, S. Coetzee, W. Matheson, A. W. Mackay e C. Harris. "Diagenetic transformations and silcrete-calcrete intergrade duricrust formation in palaeo-estuary sediments". Earth Surface Processes and Landforms 39, n. 9 (13 gennaio 2014): 1167–87. http://dx.doi.org/10.1002/esp.3516.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

28

Löhr, S. C., M. Grigorescu e M. E. Cox. "Iron nodules in ferric soils of the Fraser Coast, Australia: relicts of laterisation or features of contemporary weathering and pedogenesis?" Soil Research 51, n. 2 (2013): 77. http://dx.doi.org/10.1071/sr12372.

Testo completo

Abstract (sommario):

The genesis of ferruginous nodules and pisoliths in soils and weathering profiles of coastal southern and eastern Australia has long been debated. It is not clear whether iron (Fe) nodules are redox accumulations, residues of Miocene laterite duricrust, or the products of contemporary weathering of Fe-rich sedimentary rocks. This study combines a catchment-wide survey of Fe nodule distribution in Poona Creek catchment (Fraser Coast, Queensland) with detailed investigations of a representative ferric soil profile to show that Fe nodules are derived from Fe-rich sandstones. Where these crop out, they are broken down, transported downslope by colluvial processes, and redeposited. Chemical and physical weathering transforms these eroded rock fragments into non-magnetic Fe nodules. Major features of this transformation include lower hematite/goethite and kaolinite/gibbsite ratios, increased porosity, etching of quartz grains, and development of rounded morphology and a smooth outer cortex. Iron nodules are commonly concentrated in ferric horizons. We show that these horizons form as the result of differential biological mixing of the soil. Bioturbation gradually buries nodules and rock fragments deposited at the surface of the soil, resulting in a largely nodule-free ‘biomantle’ over a ferric ‘stone line’. Maghemite-rich magnetic nodules are a prominent feature of the upper half of the profile. These are most likely formed by the thermal alteration of non-magnetic nodules located at the top of the profile during severe bushfires. They are subsequently redistributed through the soil profile by bioturbation. Iron nodules occurring in the study area are products of contemporary weathering of Fe-rich rock units. They are not laterite duricrust residues nor are they redox accumulations, although redox-controlled dissolution/re-precipitation is an important component of post-depositional modification of these Fe nodules.

Gli stili APA, Harvard, Vancouver, ISO e altri

29

Bitom, Dieudonné, Boris Volkoff e Monique Abossolo-Angue. "Evolution and alteration in situ of a massive iron duricrust in Central Africa". Journal of African Earth Sciences 37, n. 1-2 (luglio 2003): 89–101. http://dx.doi.org/10.1016/s0899-5362(03)00044-7.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

30

Cooper, C. "Spectroscopy of Loose and Cemented Sulfate-Bearing Soils: Implications for Duricrust on Mars". Icarus 158, n. 1 (luglio 2002): 42–55. http://dx.doi.org/10.1006/icar.2002.6874.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

31

Wells, M. A., M. Danišík, B. I. A. McInnes e P. A. Morris. "(U-Th)/He-dating of ferruginous duricrust: Insight into laterite formation at Boddington, WA". Chemical Geology 522 (settembre 2019): 148–61. http://dx.doi.org/10.1016/j.chemgeo.2019.05.030.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

32

Ruprecht, JK, e NJ Schofield. "In situ neutron moisture meter calibration in lateritic soils". Soil Research 28, n. 2 (1990): 153. http://dx.doi.org/10.1071/sr9900153.

Testo completo

Abstract (sommario):

An in situ calibration procedure for complex lateritic soils of the jarrah forest of Western Australia is described. The calibration is based on non-destructive sampling of each access tube and on a regression of change in water content on change in neutron count ratio at 'wet' and 'dry' times of the year. Calibration equations with adequate precision were produced. ever, there were high residual errors in the calibration equations which were due to a number of factors including soil water variability, the presence of a duricrust layer, soil sampling of gravelly soils and the variability of the cement slurry annulus surrounding each access tube. The calibration equations derived did not compare well with those from other studies in south-west Western Australia, but there was reasonable agreement with the general equations obtained by the Institute of Hydrology, U.K.

Gli stili APA, Harvard, Vancouver, ISO e altri

33

Paz, Anat, Emma J. Gagen, Alan Levett, Yitian Zhao, Peter M. Kopittke e Gordon Southam. "Biogeochemical cycling of iron oxides in the rhizosphere of plants grown on ferruginous duricrust (canga)". Science of The Total Environment 713 (aprile 2020): 136637. http://dx.doi.org/10.1016/j.scitotenv.2020.136637.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

34

PIDGEON, R. T., T. BRANDER e H. J. LIPPOLT. "Late Miocene (U+Th)-4He ages of ferruginous nodules from lateritic duricrust, Darling Range, Western Australia". Australian Journal of Earth Sciences 51, n. 6 (dicembre 2004): 901–9. http://dx.doi.org/10.1111/j.1400-0952.2004.01094.x.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Yao Kouman Nestor, Kouakou, Gala Bi Trazie Jeremie, Yao Guy Fernand, Kouadio Kouassi Gerard e Yao-Kouame Albert. "TRAITS MORPHOPEDOLOGIQUES DUNE PENEPLAINE DE SAVANE ARBOREE A BROBO AU CENTRE DE LA COTE DIVOIRE". International Journal of Advanced Research 9, n. 10 (31 ottobre 2021): 657–62. http://dx.doi.org/10.21474/ijar01/13590.

Testo completo

Abstract (sommario):

A morphopedological study was conducted on a 10 hectares plot of land near the village of Bopri in the sub-prefecture of Brobo. The objective was to identify the soils of this site in order to have a general overview of the soils of this region, which is poorly known from a pedological point of view and where the rare information relating to the soils goes back decades. Its implementation required the opening of 7 soil pits distributed homogeneously over the entire site in order to guarantee the representativeness of the information collected during these investigations. In total, this study revealed that this site contains a large proportion of typically ferralitic soils with deep indurations Haplic Ferralsols (Endopetric). However, in addition to this dominant category, anthropogenic Leptosols are found, which are characterised by a continuous mass of duricrust starting less than 25 cm deep and whose formation is consecutive of human activities.

Gli stili APA, Harvard, Vancouver, ISO e altri

36

Singh, Yamuna, e S. D. Rai. "Yttrium-Europium-Erbium Geochemistry of Granitic Soils of Kunkuri Area, Raigarh District, Madhya Pradesh, India". Journal Geological Society of India 40, n. 4 (1 ottobre 1992): 347–58. http://dx.doi.org/10.17491/jgsi/1992/400404.

Testo completo

Abstract (sommario):

Abstract The duricrust and the soils derived from the Precambrian granitic rocks of Kunkuri area in Raigarh district, Madhya Pradesh, contain anomalous concentratioIis of rare earth and yttrium minerals. The polymineral table concentrates obtained from the granitic soil contain xenotime, monazite, zircon, Hmenite and rutile. Chemical analyses of table concentrate indicate values up to 3.08% Y 203.0.30% Er203 and 0.0286% EU203 in the ratio of 10 : 1 : 0.1. Corresponding data on table concentrates from the source granitic rocks also demonstrate a similar form in Y 203 : Er203 : EU203' Y/Er ratio is 10. which is similar to the average granites, while Er/Eu ratio of 10 is anomalously high, being 4 times the average for granitic rocks. Since the REE and Y bearing minerals are radioactive and contribute to a major part of the radioactivity in soHI alluvial deposits of the areas investigated, aeroradiometric surveys fonowed by ground radiometric checkings, preferably along 2nd to 5th order streams in the adjoining areas, are recommended.

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Yoboue, Kouadio Emile, Bi Trazié Jérémie Gala, Marie-Paule Hien e Kouassi Yannick Stéphane Gboko. "Pédo-géochimie et minéralogie des sols à cuirassement sur substrat sédimentaire de Bingerville, au nord-est du district d’Abidjan, Côte d’Ivoire". International Journal of Biological and Chemical Sciences 17, n. 6 (18 gennaio 2024): 2525–35. http://dx.doi.org/10.4314/ijbcs.v17i6.30.

Testo completo

Abstract (sommario):

Pour déterminer la dynamique pédo-géochimique du cuirassement des sols sur le bassin sédimentaire de Côte d’Ivoire, des échantillons de sol et des indurations ont été prélevés à Bingerville, analysés au spectromètre à fluorescence X et au diffractomètre à rayons X. Les résultats ont révélé que les oxydes de silicium (SiO2), de fer (Fe2O3) et d’aluminium (Al2O3) étaient les principaux constituants des sols et des formations indurées. Dans les sols et les croûtes, en plus de la silice (27-62%), il s’y observait une forte concentration de chrome (420 à 1890 ppm) dans les échantillons. Par contre dans les cuirasses, ce sont les oxydes de fer (18-57%), le nickel (80 à 108 ppm), le plomb (64 ppm) et le Cadmium (30 ppm) qui étaient les plus concentrés. Au niveau minéralogique, les sols et les indurations étaient principalement constitués du quartz (environ 70%) et d’hématite (environ 4%) pour les oxydes et de kaolinite (24-33%) pour les minéraux argileux. Les indurations observées sur substrat sédimentaire sont assimilables au niveau pédo-géochimique à celles développées sur le socle protérozoïque du Centre et du Nord de la Côte d’Ivoire mais, leurs teneurs en ETM pourraient constituer des sources de toxicité pour les populations. To determine the pedo-geochemical dynamic of soil duricrust in sedimentary basins in Côte d'Ivoire, soil samples were taken in Bingerville and analysed using an X-ray fluorescence spectrometer and an X-ray diffractometer. The results showed that oxides of silicon (SiO2), iron (Fe2O3) and aluminium (Al2O3) were the main constituents of the soils and indurated formations. In the soils and crusts, in addition to silica (27-62%), there was a high concentration of chromium (420 to 1890 ppm) in the samples. However, in the duricrusts, iron oxides (18-57%), nickel (80 to 108 ppm), lead (64 ppm) and Cdmium (30 ppm) were the most concentrated. Mineralogically, the soils and indurations were mainly composed of quartz (around 70%) and hematite (around 4%) for the oxides and kaolinite (24-33%) for the clay minerals. The indurations observed on sedimentary substrates are comparable at the pedo-geochemical level to those developed on Proterozoic bedrock in central and northern Côte d'Ivoire, but their TME content could be a source of toxicity for local populations.

Gli stili APA, Harvard, Vancouver, ISO e altri

38

Bustillo, M. A., e E. García Romero. "Arcillas fibrosas anómalas en encostramientos y sedimentos superficiales: características y génesis (Esquivias, Cuenca de Madrid)". Boletín de la Sociedad Española de Cerámica y Vidrio 42, n. 5 (30 ottobre 2003): 289–97. http://dx.doi.org/10.3989/cyv.2003.v42.i5.632.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Girard, Jean-Pierre, Philippe Freyssinet e Anne-Claire Morillon. "Oxygen isotope study of Cayenne duricrust paleosurfaces: implications for past climate and laterization processes over French Guiana". Chemical Geology 191, n. 4 (novembre 2002): 329–43. http://dx.doi.org/10.1016/s0009-2541(02)00130-4.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

40

dos Santos Albuquerque, Márcio Fernando, Adriana Maria Coimbra Horbe e Martin Danišík. "Episodic weathering in Southwestern Amazonia based on (U Th)/He dating of Fe and Mn lateritic duricrust". Chemical Geology 553 (ottobre 2020): 119792. http://dx.doi.org/10.1016/j.chemgeo.2020.119792.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

41

Levett, Alan, Paulo M. Vasconcelos, Michael M. W. Jones, Llew Rintoul, Anat Paz, Emma J. Gagen e Gordon Southam. "Titanium mobility preserved in association with microfossils in an iron-rich duricrust capping an iron ore deposit". Chemical Geology 559 (gennaio 2021): 119955. http://dx.doi.org/10.1016/j.chemgeo.2020.119955.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

42

Shuster, David L., Kenneth A. Farley, Paulo M. Vasconcelos, Greg Balco, Hevelyn S. Monteiro, Kathryn Waltenberg e John O. Stone. "Cosmogenic 3He in hematite and goethite from Brazilian “canga” duricrust demonstrates the extreme stability of these surfaces". Earth and Planetary Science Letters 329-330 (maggio 2012): 41–50. http://dx.doi.org/10.1016/j.epsl.2012.02.017.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

43

Som, S. K., R. Joshi, P. K. Roy e M. M. Mukherjee. "Morphotectonic Evolution of the Laterite Profiles over Sukinda Ultramafics, Jaipur District, Orissa". Journal Geological Society of India 52, n. 4 (1 ottobre 1998): 449–56. http://dx.doi.org/10.17491/jgsi/1998/520408.

Testo completo

Abstract (sommario):

Abstract Sukinda ultramafic field of Jajpur district, Orissa is capped by thick lateritic duricrust. Two generations of laterite are inferred in the studied area. The older laterite (in situ) is capped by transported laterite (younger). The entire area is divided into two subareas (A1 and A2) Physiographically, three terraces are identified in A1 area, of which, the oldest one (T3) comprises of insitu lateritic hard crust. The other two terraces (T2 and T1) are made up of valley fill deposits, which are later lateritised. The area A2 shows the lateral continuity of T3 terrace of A1 area along with valley fill deposit of T1 terrace and the absence of T2 terrace. Drainage analysis show the A1 area is structurally more disturbed than A2 area. Correlation of geomorphological evolution and lateritisation indicates three stages of development in the A1 area. Lateritisation was initiated on a comparatively flat ground (T3 terrace) and subsequent destabilisation of the area developed the younger terraces (T2 and T1) with the modification of older laterite profile.

Gli stili APA, Harvard, Vancouver, ISO e altri

44

Gagen, Emma J., Alan Levett, Anat Paz, Markus Gastauer, Cecílio Frois Caldeira, Rafael Borges da Silva Valadares, José Augusto Pires Bitencourt et al. "Biogeochemical processes in canga ecosystems: Armoring of iron ore against erosion and importance in iron duricrust restoration in Brazil". Ore Geology Reviews 107 (aprile 2019): 573–86. http://dx.doi.org/10.1016/j.oregeorev.2019.03.013.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

45

Cabral, Alexandre Raphael, Adriana Zapparoli, Eduardo Geraldo Melo Motta e Rogerio Kwitko-Ribeiro. "Coarse-grained siderite in canga, Quadrilátero Ferrífero of Minas Gerais, Brazil: mineralogical evidence for the longevity of ferruginous duricrust". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 265, n. 3 (1 settembre 2012): 305–14. http://dx.doi.org/10.1127/0077-7749/2012/0269.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

46

Souza-Filho, Pedro Walfir M., José Tasso F. Guimarães, Marcio S. Silva, Francisco R. Costa, Prafulla K. Sahoo, Clovis W. Maurity e Roberto Dall’Agnol. "Basin morphology, sedimentology and seismic stratigraphy of an upland lake from Serra dos Carajás, southeastern Amazon, Brazil". Boletim do Museu Paraense Emílio Goeldi - Ciências Naturais 11, n. 1 (18 gennaio 2021): 71–83. http://dx.doi.org/10.46357/bcnaturais.v11i1.461.

Testo completo

Abstract (sommario):

To understand the sedimentary processes in a lake environment, it is essential to investigate the morphological, sedimentalogical and limnological features of the basin. The present study was developed at Violão Lake, Serra Sul de Carajás. The methodological approach comprises the collection of bathymetric and sedimentary data, and shallow seismic profiles. Lake Violão has a NE-SW elongated guitar-shaped form and ~0.3 km2 of surface area, with a perimeter of ~2.7 km. The lake presents washing basin morphology and it is marked by a steep margin carved in duricrust outcrops, while the bottom is flat and constituted mainly by muddy sediments. The water column is stratified only during the dry season and it is mixed in the rainy season. Three seismic stratigraphic successions were identified in the lake resting on prominent basal reflector (bedrock), which reaches a maximum depth of ~15 m. Small lobate masses are deposited in the bottom of the lake from underflows, while the central part of the lake is characterized by drape deposition, suggesting that organic-mud sedimentation is associated to pelagic deposition from dilute interflows or overflows. Therefore, the sedimentary processes are strongly regulated by basin morphology, drainage water inflow and thermal stratification of the water column.

Gli stili APA, Harvard, Vancouver, ISO e altri

47

Zhao, Dong, Wei Lu, Yulan Wang, Xiaofei Mao, Yu Ai e Haotian Jiang. "Experimental Studies on Earthen Architecture Sites Consolidated with BS Materials in Arid Regions". Advances in Materials Science and Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/6836315.

Testo completo

Abstract (sommario):

This paper takes the preservation works on the archaeological sites of Gaochang Ruins, Xinjiang, as background. Based on the soil characteristics analysis on the archaeological sites, experimental studies were conducted on the consolidation effect of the BS-10 consolidation material on the archaeological sites of adobe and rammed earth. The results showed the following:, after consolidation, the wind erosion resistance of the soil on the archaeological sites was substantially increased, and the wind erosion modulus was reduced by 5~8 times; the soil exhibited fine grid structure and significantly reduced degree of permeability, while still maintaining the moisture exchange between inside and outside the soil; there is excellent ageing resistance; the resistance to freezing and thawing was closely related to the soil water content and had little influence in arid regions; the water resistance was improved and could satisfy the requirements for consolidating the sites in arid regions; the unconfined compressive strength was improved moderately, which was the key direction of improvement in the future, and the consolidated soil did not form duricrust on the surface and had good bonding strength with the internal parts. The BS-10 material can meet the consolidation requirements for the earthen archaeological sites in arid regions of northwest China.

Gli stili APA, Harvard, Vancouver, ISO e altri

48

Théveniaut, H., e Ph Freyssinet. "Paleomagnetism applied to lateritic profiles to assess saprolite and duricrust formation processes: the example of Mont Baduel profile (French Guiana)". Palaeogeography, Palaeoclimatology, Palaeoecology 148, n. 4 (maggio 1999): 209–31. http://dx.doi.org/10.1016/s0031-0182(98)00183-7.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

49

Sini, André, Simon Djakba Basga, Jean Pierre Temga e Jean Pierre Nguetnkam. "The influence of topography in duricrust development in the Ngaoundal-Dir section of central Cameroon: Understanding morphological, mineralogical and geochemical transformations". Scientific African 10 (novembre 2020): e00655. http://dx.doi.org/10.1016/j.sciaf.2020.e00655.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

50

Austrheim, Håkon, Depan Hu, Ole Ivar Ulven e Niels H. Andersen. "Formation of Natural Magnesium Silica Hydrate (M-S-H) and Magnesium Alumina Silica Hydrate (M-A-S-H) Cement". Materials 17, n. 5 (21 febbraio 2024): 994. http://dx.doi.org/10.3390/ma17050994.

Testo completo

Abstract (sommario):

Occurrences of natural magnesium alumina silicate hydrate (M-(A)-S-H) cement are present in Feragen and Leka, in eastern and western Trøndelag Norway, respectively. Both occurrences are in the subarctic climate zone and form in glacial till and moraine material deposited on ultramafic rock during the Weichselian glaciation. Weathering of serpentinized peridotite dissolves brucite and results in an alkaline fluid with a relatively high pH which subsequently reacts with the felsic minerals of the till (quartz, plagioclase, K-feldspar) to form a cement consisting of an amorphous material or a mixture of nanocrystalline Mg-rich phyllosilicates, including illite. The presence of plagioclase in the till results in the enrichment of alumina in the cement, i.e., forms M-A-S-H instead of the M-S-H cement. Dissolution of quartz results in numerous etch pits and negative quartz crystals filled with M-A-S-H cement. Where the quartz dissolution is faster than the cement precipitation, a honeycomb-like texture is formed. Compositionally, the cemented till (tillite) contains more MgO and has a higher loss of ignition than the till, suggesting that the cement is formed by a MgO fluid that previously reacted with the peridotite. The M-(A)-S-H cemented till represents a new type of duricrust, coined magsilcrete. The study of natural Mg cement provides information on peridotites as a Mg source for Mg cement and as a feedstock for CO2 sequestration.

Gli stili APA, Harvard, Vancouver, ISO e altri

Offriamo sconti su tutti i piani premium per gli autori le cui opere sono incluse in raccolte letterarie tematiche. Contattaci per ottenere un codice promozionale unico!