scholarly journals Utilisation du 10 Be cosmogenique produit in-situ pour l'etude de la dynamique et de l'evolution des sols en milieux lateritiques

2000 ◽  
Vol 171 (5) ◽  
pp. 511-520 ◽  
Author(s):  
Regis Braucher ◽  
Lionel Siame ◽  
Didier Bourles ◽  
Fabrice Colin
Keyword(s):  
Cosmic Rays ◽  
Nuclear Reactions ◽  
Lateral Displacement ◽  
Soil Formation ◽  
Soil Profiles ◽  
Surface Material ◽  
Quartz Veins ◽  
Denudation Rates ◽  
Lateral Variations

Abstract In situ-produced cosmonuclides result from nuclear reactions between cosmic-rays derived particles and the elements constituting the Earth's surface material. Cosmogenic 10 Be (T1/2 = 1,5Ma) and 26 Al (T1/2 = 0.73 Ma) produced within the quartz mineral fraction of surficial rocks have been used to quantitatively study the emplacement and development of laterites. Depth distributions of in situ-produced 10 Be along quartz veins and soil profiles permit: (1) to clarify mechanisms involved in soil formation and landform evolutions, (2) to quantify burial or denudation rates. Lateral variations of the in situ-produced 10 Be concentration along stone-lines allow to determine whether the stone-line constituting material has an allochthonous or an autochthonous origin, and, in the latter case, to estimate the lateral displacement rates.

Weathering and soil formation on dolerite in Tasmania with particular reference to several trace elements

Soil Research ◽  
1963 ◽  
Vol 1 (1) ◽  
pp. 74 ◽  
Author(s):  
KG Tiller
Keyword(s):  
Trace Elements ◽  
Soil Formation ◽  
Fine Sand ◽  
Climatic Conditions ◽  
Parent Material ◽  
Soil Profiles ◽  
Podzolic Soils ◽  
Nickel Copper ◽  
Soil Groups

The mineralogy and chemistry of weathering and soil formation have been studied at 17 widely separated sites with contrasting climatic conditions on comparatively uniform dolerite in Tasmania. The clay and fine sand mineralogy of the soils has been related to their degree of weathering. These studies have shown large chemical and mineralogical changes accompanying the initial stages of weathering in some krasnozem soils. The reorganization of cobalt, zirconium, nickel, copper, molybdenum, manganese, and zinc during genesis of four soil groups has been considered in terms of the factors involved. Some of these results indicate that the clay horizon of the podzolic soils has probably been formed by weathering in situ. Seasonal waterlogging in certain horizons has strongly mfluenced the chemistry and mineralogy of weathering in many of these soils. This study has shown that the composition of the parent material has only influenced the geochemistry of trace elements in less weathered soils and that pedogenic factors assumed greater significance as the soils became more strongly weathered. Geomorphic processes had a marked influence on the geochemistry of some soils by the truncation of mature soil profiles.

scholarly journals Denudation systematics inferred from in situ cosmogenic <sup>10</sup>Be concentrations in fine (50–100 µm) and medium (100–250 µm) sediments of the Var River basin, southern French Alps

2019 ◽  
Vol 7 (4) ◽  
pp. 1059-1074 ◽  
Author(s):  
Apolline Mariotti ◽  
Pierre-Henri Blard ◽  
Julien Charreau ◽  
Carole Petit ◽  
Stéphane Molliex ◽  
...  
Keyword(s):  
Glacial Cycles ◽  
Size Fractions ◽  
French Alps ◽  
Fine Grained ◽  
Denudation Rates ◽  
Variable Morphology ◽  
Cosmogenic 10Be ◽  
The Impact ◽  
Quartz Grains

Abstract. Marine sedimentary archives are well dated and often span several glacial cycles; cosmogenic 10Be concentrations in their detrital quartz grains could thus offer the opportunity to reconstruct a wealth of past denudation rates. However, these archives often comprise sediments much finer (<250 µm) than typically analyzed in 10Be studies, and few studies have measured 10Be concentrations in quartz grains smaller than 100 µm or assessed the impacts of mixing, grain size, and interannual variability on the 10Be concentrations of such fine-grained sediments. Here, we analyzed the in situ cosmogenic 10Be concentrations of quartz grains in the 50–100 and 100–250 µm size fractions of sediments from the Var basin (southern French Alps) to test the reliability of denudation rates derived from 10Be analyses of fine sands. The Var basin has a short transfer zone and highly variable morphology, climate, and geology, and we test the impact of these parameters on the observed 10Be concentrations. Both analyzed size fractions returned similar 10Be concentrations in downstream locations, notably at the Var's outlet, where concentrations ranged from (4.02±0.78)×104 to (4.40±0.64)×104 atoms g−1 of quartz. By comparing expected and observed 10Be concentrations at three major river junctions, we interpret that sediment mixing is efficient throughout the Var basin. We resampled four key locations 1 year later, and despite variable climatic parameters during that period, interannual 10Be concentrations were in agreement within uncertainties, except for one upper subbasin. The 10Be-derived denudation rates of Var subbasins range from 0.10±0.01 to 0.57±0.09 mm yr−1, and spatial variations are primarily controlled by the average subbasin slope. The integrated denudation rate of the entire Var basin is 0.24±0.04 mm yr−1, in agreement with other methods. Our results demonstrate that fine-grained sediments (50–250 µm) may return accurate denudation rates and are thus potentially suitable targets for future 10Be applications, such as studies of paleo-denudation rates using offshore sediments.

The origins of kaolinite-rich rocks associated with coal measures in China

Clay Minerals ◽  
2001 ◽  
Vol 36 (3) ◽  
pp. 389-402 ◽  
Author(s):  
Qinfu Liu ◽  
D. A. Spears ◽  
Pengfei Zhang ◽  
Hongliang Xu
Keyword(s):  
Land Surface ◽  
Volcanic Ashes ◽  
Chinese Coal ◽  
Coal Measures ◽  
Lateral Variations

AbstractKaolinite-rich rocks are widespread in Chinese coal-bearing strata. Three main types of deposits are recognized. Those deposits identified as flint clays are several metres thick and show lateral variations in bed composition. The kaolinite is thought to have formed mainly on the adjacent landmass, but some crystallization of gels within the basin is not ruled out. Tonsteins, which formed from the in situ alteration of airfall volcanic ashes, are very common in the coal measures and are up to 0.5 m thick. Finally, kaolinite deposits are described where the development of kaolin is related to weathering of coals either close to or at the present land surface.

scholarly journals <sup>10</sup>Be depth profiles in glacial sediments on the Swiss Plateau: deposition age, denudation and (pseudo-) inheritance

2017 ◽  
Vol 66 (2) ◽  
pp. 57-68 ◽  
Author(s):  
Lorenz Wüthrich ◽  
Claudio Brändli ◽  
Régis Braucher ◽  
Heinz Veit ◽  
Negar Haghipour ◽  
...  
Keyword(s):  
Radioactive Decay ◽  
Glacial Sediments ◽  
Depth Profiles ◽  
Denudation Rates ◽  
Last Glaciation ◽  
The Alps ◽  
Swiss Plateau ◽  
High Concentrations ◽  
Cosmogenic 10Be

Abstract. During the Pleistocene, glaciers advanced repeatedly from the Alps onto the Swiss Plateau. Numeric age control for the last glaciation is good and thus the area is well suited to test a method which has so far not been applied to till in Switzerland. In this study, we apply in situ produced cosmogenic 10Be depth profile dating to several till deposits. Three sites lie inside the assumed Last Glacial Maximum (LGM) extent of the Rhône and Aare glaciers (Bern, Deisswil, Steinhof) and two lie outside (Niederbuchsiten, St. Urban). All sites are strongly affected by denudation, and all sites have reached steady state, i.e., the 10Be production is in equilibrium with radioactive decay and denudational losses. Deposition ages can therefore not be well constrained. Assuming constant denudation rates of 5 cm kyr−1, total denudation on the order of 100 cm for sites within the extent of the LGM and up to tens of meters for older moraines are calculated. Denudation events, for example related to periglacial conditions during the LGM, mitigate the need to invoke such massive denudation and could help to explain high 10Be concentrations at great depths, which we here dub pseudo-inheritance. This term should be used to distinguish conceptionally from true inheritance, i.e., high concentrations derived from the catchment.

Patchy bedrock explained: Tectonic fracture control on landscape evolution patterns in south-Central Chile 

2021 ◽  
Author(s):  
Emma Lodes ◽  
Dirk Scherler ◽  
Hella Wittmann ◽  
Renee Van Dongen
Keyword(s):  
Chemical Weathering ◽  
Landscape Evolution ◽  
Tectonic Deformation ◽  
Fracture Density ◽  
Rock Fracturing ◽  
Central Chile ◽  
Erosion Rates ◽  
Denudation Rates ◽  
South Central

&lt;p&gt;Rock fracturing induced by tectonic deformation is thought to promote faster denudation in more highly fractured areas by lowering grain size and directing the flow of water. That the density and pattern of fractures in a landscape play a role in controlling erosion and landscape evolution has been known for over a century, but not until recently do we have tools, like cosmogenic nuclides, to quantify erosion rates in places with varying fracture densities. In the Nahuelbuta Range in south-central Chile, we observed that &gt;30-m thick regolith exists next to patches of unweathered bedrock. We hypothesize that the density of fractures dictates the pace and patterns of chemical weathering, regolith conversion, and erosion in the Nahuelbuta Range. To test this, we used in situ cosmogenic &lt;sup&gt;10&lt;/sup&gt;Be to obtain denudation rates from amalgamated samples of bedrock, corestones and soils, and measured fracture density and orientation, as well as hillslope boulder size in several sites in the Nahuelbuta Range. We found that more highly fractured areas indeed have higher denudation rates than less fractured areas, and that bedrock denudation rates are ~10 m/Myr while soil denudation rates are ~30 m/Myr, suggesting that soil-covered areas may be sites of higher fracture density at depth. Fractures have orientations that match mapped faults across the Nahuelbuta range, and thus are considered to be tectonically-induced. In addition, both fracture and fault orientations match the orientation of streams incising the range, suggesting that fractures control stream channel orientation by weakening bedrock and thus directing flow.&lt;/p&gt;

scholarly journals A Review of In Situ Isotopic Studies of the Oklo and Bangombé Natural Fission Reactors Using Microbeam Analytical Techniques

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1060
Author(s):  
Hiroshi Hidaka
Keyword(s):  
Nuclear Reactions ◽  
Fission Products ◽  
Analytical Techniques ◽  
Laser Probe ◽  
The Past ◽  
Isotopic Analyses ◽  
Isotopic Studies ◽  
Reactor Materials ◽  
Fission Reactors

Isotopic analyses of elements in the natural reactor materials have often been performed to understand the distribution behaviors of the fission products and to evaluate the function of nuclear reactions since the first discovery of a natural reactor in 1972. Several types of unique microminerals, including significant amounts of fission products, have been found in and around the Oklo and the Bangombé natural reactors. In the past two decades, microbeam techniques using ion and laser probe facilities have been effectively applied for the in situ isotopic analyses of individual microminerals to investigate the migration behaviors of fissiogenic radioisotopes produced in the reactors. This paper presents a review of interpretations of the isotopic results of microminerals found in and around the natural reactors.

Influence of soil redox conditions on oxidation of biotite

Clay Minerals ◽  
1986 ◽  
Vol 21 (2) ◽  
pp. 149-157 ◽  
Author(s):  
S. Bouda ◽  
K. P. Isaac
Keyword(s):  
Mössbauer Spectroscopy ◽  
Soil Profile ◽  
Mossbauer Spectroscopy ◽  
Redox Conditions ◽  
Soil Profiles ◽  
Moderate Degree ◽  
Soil Redox ◽  
Mößbauer Spectroscopy

AbstractBiotites from three peaty gleyed podzol soil profiles on ranite bedrock were examined to investigate the oxidation of the octahedral Fe during weathering. Oxidation of these biotites as determined by Mössbauer spectroscopy shows a good correlation with the in situ measured soil Eh values of the sampled horizons. In every soil profile the highest Eh measured is in the A horizon and the lowest in the C horizon. Similarly, biotites from the A horizons are the most oxidized compared with those from the lower horizons. In most of the samples the oxidation is accompanied by loss of K+ from the lattice, as demonstrated by a moderate degree of vermiculitization.

Addressing solar modulation and long-term uncertainties in scaling secondary cosmic rays for in situ cosmogenic nuclide applications

2005 ◽  
Vol 239 (1-2) ◽  
pp. 140-161 ◽  
Author(s):  
Nathaniel A. Lifton ◽  
John W. Bieber ◽  
John M. Clem ◽  
Marc L. Duldig ◽  
Paul Evenson ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Solar Modulation ◽  
Cosmogenic Nuclide

scholarly journals Uncertainties in νp-process nucleosynthesis from Monte Carlo variation of reaction rates

2019 ◽  
Vol 489 (1) ◽  
pp. 1379-1396 ◽  
Author(s):  
N Nishimura (西村信哉) ◽  
T Rauscher ◽  
R Hirschi ◽  
G Cescutti ◽  
A St J Murphy ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Large Scale ◽  
Nuclear Reactions ◽  
Model Identification ◽  
Reaction Rates ◽  
Parameter Study ◽  
Unstable Nuclei ◽  
Hydrodynamic Evolution ◽  
Isotopic Abundances

ABSTRACT It has been suggested that a νp-process can occur when hot, dense, and proton-rich matter is expanding within a strong flux of antineutrinos. In such an environment, proton-rich nuclides can be produced in sequences of proton captures and (n, p) reactions, where the free neutrons are created in situ by $\overline{\nu }_\mathrm{e}+\mathrm{p} {\rightarrow} \mathrm{n}+\mathrm{e}^+$ reactions. The detailed hydrodynamic evolution determines where the nucleosynthesis path turns off from N = Z line and how far up the nuclear chart it runs. In this work, the uncertainties on the final isotopic abundances stemming from uncertainties in the nuclear reaction rates were investigated in a large-scale Monte Carlo approach, simultaneously varying more than 10 000 reactions. A large range of model conditions was investigated because a definitive astrophysical site for the νp-process has not yet been identified. The present parameter study provides, for each model, identification of the key nuclear reactions dominating the uncertainty for a given nuclide abundance. As all rates appearing in the νp-process involve unstable nuclei, and thus only theoretical rates are available, the final abundance uncertainties are larger than those for nucleosynthesis processes closer to stability. Nevertheless, most uncertainties remain below a factor of 3 in trajectories with robust nucleosynthesis. More extreme conditions allow production of heavier nuclides but show larger uncertainties because of the accumulation of the uncertainties in many rates and because the termination of nucleosynthesis is not at equilibrium conditions. It is also found that the solar ratio of the abundances of 92Mo and 94Mo could be reproduced within uncertainties.

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