Clay mineralogy in southern Africa river muds

AbstractThe composition, morphology and crystal order of clay minerals in silt-sized sediments carried in suspensions from 25 major rivers across tropical southern Africa have been studied by X-ray diffractometry and scanning and transmission electron microscopy. Our goal was to determine the spatial variability of clay-mineral associations in diverse geological settings, and in climatic conditions ranging from humid Angola and Zambia to hyperarid Namibia and the Kalahari. Specific attention was paid to the micromorphology and chemical composition of smectite particles. The relative abundance of smectites, illite/mica, kaolinite and chlorite enabled identification of regions characterized by different physical and chemical processes: (1) negligible chemical weathering is documented in Namibia, where river muds mostly contain illite/mica or smectite derived from Damara metasedimentary or Etendeka volcanic rocks; (2) kaolinite documenting intense weathering, reaches a maximum in the Okavango, Kwando and Upper Zambezi, sourced in subequatorial Angola and Zambia; (3) suspended-load muds in the Limpopo and middle Zambezi catchments display intermediate features, with varied assemblages and smectite compositions reflecting diverse parent lithologies. Clay mineralogy and chemical composition are confirmed as a most effective tool to unravel present and past climatic conditions on a continental scale.

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Late Cretaceous—Palaeocene mid-latitude climates: inferences from clay mineralogy of continental-coastal sequences (Tremp-Graus area, southern Pyrenees, N Spain)

Clay Minerals ◽

10.1180/claymin.2011.046.1.105 ◽

2011 ◽

Vol 46 (1) ◽

pp. 105-126 ◽

Cited By ~ 15

Author(s):

J. Arostegi ◽

J. I. Baceta ◽

V. Pujalte ◽

M. Carracedo

Keyword(s):

Clay Mineral ◽

Chemical Weathering ◽

Clay Mineralogy ◽

Source Area ◽

Climatic Conditions ◽

Sem Images ◽

Climatic Trend ◽

Mineral Associations ◽

Continental Basin ◽

Mixed Layers

AbstractThe origin and distribution of late Maastrichtian–early Palaeocene clay mineral associations were investigated in the Tremp-Graus basin (South Pyrenees, Spain) to assess palaeoclimate changes during that period. The studied succession is made up of expanded continental and transitional terrigeneous and carbonate deposits accumulated in a coastal plain setting. X-ray diffraction, SEM-EDX and TEM-AEM analysis reveal that the main clay components are illite and smectite, but kaolinite, chlorite and illite-smectite mixed layers are present, although irregularly distributed, all of them showing a platy morphology typical of a detrital origin. Persistence of the chemical features of the Al-dioctahedral smectites throughout the whole succession demonstrates the persistence of the same source area during the interval studied. Palygorskite occurs in the late Danian and Selandian, within carbonate tidal flats as sabkha-like facies. In SEM images, the palygorskite displays straight fibre morphologies, both coating and branched curling out, a clear proof of authigenic origin.Physical or chemical weathering (PhW/ChW) determined as illite + chlorite/smectite + kaolinite ratio, smectite/kaolinite ratio and palygorskite distribution have been used as clay proxies for palaeoclimate reconstructions. Such data suggest a shift from temperate subhumid (perennial) conditions in late Maastrichtian times to a warm seasonal climate during early Palaeocene times. This trend, however, was dramatically altered during the late Danian–Selandian interval, when prevailing warm and semi-arid to arid climatic conditions caused intense evaporation and the development of an alkaline environment in which the palygorskite authigenesis took place.The proposed climatic trend partly concurs with that established for earliest Danian time by Domingoet al.(2007), also in the Tremp-Graus basin, from isotopic and geochemical proxies, as well as with the reconstruction of Cojan & Moreau (2006), in which a semiarid Danian phase for the near continental basin of Aix-en-Provence is postulated. However, it is at odds with the notion of a humid Danian state in the Pyrenees, as inferred by Gawendaet al.(1999) from clay mineral proxies of deep marine successions.

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Peat decomposition – shaping factors, significance in environmental studies and methods of determination; a literature review

Geologos ◽

10.1515/logos-2016-0005 ◽

2016 ◽

Vol 22 (1) ◽

pp. 61-69 ◽

Cited By ~ 11

Author(s):

Danuta Drzymulska

Keyword(s):

Chemical Composition ◽

Literature Review ◽

Ground Water ◽

Environmental Conditions ◽

Meteoric Water ◽

Climatic Conditions ◽

Review Of Literature ◽

Forming Process ◽

Physical And Chemical

Abstract A review of literature data on the degree of peat decomposition – an important parameter that yields data on environmental conditions during the peat-forming process, i.e., humidity of the mire surface, is presented. A decrease in the rate of peat decomposition indicates a rise of the ground water table. In the case of bogs, which receive exclusively atmospheric (meteoric) water, data on changes in the wetness of past mire surfaces could even be treated as data on past climates. Different factors shaping the process of peat decomposition are also discussed, such as humidity of the substratum and climatic conditions, as well as the chemical composition of peat-forming plants. Methods for the determination of the degree of peat decomposition are also outlined, maintaining the division into field and laboratory analyses. Among the latter are methods based on physical and chemical features of peat and microscopic methods. Comparisons of results obtained by different methods can occasionally be difficult, which may be ascribed to different experience of researchers or the chemically undefined nature of many analyses of humification.

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Mineralogy and genesis of the Ni–Co lateritic regolith deposit of the Çaldağ area (Manisa, western Anatolia), Turkey

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2017-0184 ◽

2018 ◽

Vol 55 (3) ◽

pp. 252-271 ◽

Cited By ~ 1

Author(s):

Cahit Helvacı ◽

Tolga Oyman ◽

İbrahim Gündoğan ◽

Hasan Sözbilir ◽

Osman Parlak ◽

...

Keyword(s):

Chemical Weathering ◽

Middle Eocene ◽

Volcanic Rocks ◽

Polarized Light ◽

Ultramafic Rocks ◽

Western Anatolia ◽

Fe Oxides ◽

Transmission Electron ◽

Dry Conditions ◽

Geochemical Analyses

The Çaldağ Ni–Co deposit is characterized by a reddish brown oxide lateritic regolith, containing residual Ni deposit formed by the intense tropical weathering of peridotites. Nickel–Co ore is associated with transported ferricrete during the late Paleocene – middle Eocene, represented by colloform Fe oxides and residual lateritization during the Oligocene. The lateritic regoliths are developed over dunitic ultramafic rocks and consist mainly of smectite, berthierine, kaolinite, gypsum, pyrite, takovite, and pecoraite. These units were examined using polarized-light microscopy, X-ray diffraction, scanning and transmission electron microscopy, and geochemical methods. Mineralogical zonation from the base of the profile upwards has the following zones: ultramafic bedrocks, serpentinized ultramafic rocks (saprock), saprolite, carbonate- and sulfide-bearing zone, ferruginous saprolite zone, and silcrete. In addition, Fe oxides, smectite and opal-CT, and quartz increase towards the surface, whereas olivine, pyroxene, and serpentine decrease upwards in response to chemical weathering. Nickel–Co mineralization associated with Fe oxides and smectitic clays formed under wet and dry conditions, respectively, as a result of an increased Fe2O3 + Al2O3 + Ni + Co/MgO ratio. Field observations and mineralogical and geochemical analyses reveal that the smectite formed under basic conditions was controlled by multistage chemical weathering of ultramafic and volcanic rocks and by the concentrations of Si, Al, Fe, and Mg. Locally, concentrations of S in conjunction with Fe and Ca resulted in precipitation of goethite–hematite, gypsum, and pyrite in dissolution voids in association with smectite under acidic conditions that developed in a well-drained system.

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Clay-Mineral Assemblages from Late Quaternary Deposits on Vancouver Island, Southwestern British Columbia, Canada

Quaternary Research ◽

10.1016/0033-5894(89)90084-7 ◽

1989 ◽

Vol 31 (1) ◽

pp. 41-56 ◽

Cited By ~ 8

Author(s):

Bertrand Blaise

Keyword(s):

Clay Minerals ◽

Clay Mineral ◽

Late Quaternary ◽

Sedimentary Environment ◽

Volcanic Rocks ◽

Clay Mineralogy ◽

Vancouver Island ◽

Climatic Conditions ◽

Glacial Deposits ◽

Mineral Contents

AbstractOn Vancouver Island, the Dashwood Drift, Cowichan Head Formation, Quadra Sand, and Vashon Drift were deposited during late Pleistocene glacial and interstadial periods and show large variations in clay-mineral contents partly related to changing climatic conditions. Glacial deposits are characterized by iron-rich chlorite, illite (both well crystallized), and smectite with a morphology reflecting rapid derivation from volcanic rocks. The clay mineralogy of nonglacial deposits is more complex, and is marked by the presence of vermiculite, kaolinite, halloysite, and irregular mixed-layer minerals. Nonglacial clay minerals are poorly preserved and show a higher state of alteration due to pedogenesis. Large variations in nonglacial deposits compared to glacial deposits are also due to secondary factors such as selective sorting, soil and rock source variations, differences in sedimentary environment, and diagenesis. These secondary factors do not seem to obliterate significantly the climatic imprint on the clay minerals. These studies also permit the recognition of glacially reworked sediments, the determination of relationships between two units in the same section, and the establishment of the conditions of clay-mineral formation.

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Major element geochemistry of European agricultural soil: weathering processes of silicate parent materials

10.5194/egusphere-egu21-8412 ◽

2021 ◽

Author(s):

Philippe Negrel ◽

Anna Ladenberger ◽

Clemens Reimann ◽

Alecos Demetriades ◽

Manfred Birke ◽

...

Keyword(s):

Chemical Composition ◽

Agricultural Soil ◽

Chemical Weathering ◽

Large Scale ◽

Secondary Products ◽

Transfer Coefficients ◽

Parent Materials ◽

Weathering Processes ◽

Continental Scale ◽

Weathering Indices

Collection of agricultural soil samples in Europe (0&#8211;20 cm, 33 countries, 5.6 million km2) during the GEMAS (GEochemical Mapping of Agricultural and grazing land Soil) continental-scale project allowed the study of geochemical behaviour of major elements during weathering (SiO2, TiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, P2O5) using their total concentrations (XRF data). The chemical composition of soil represents to a large extent the primary mineralogy of the source bedrock, the effects of pre- and post-depositional weathering and element mobility, either by leaching or mineral sorting with the addition of formation of secondary products such as clays.Bulk geochemistry is used to calculate a set of weathering indices such as chemical index of alteration CIA, reductive and oxidative mafic index of alteration MIA, the change in mass balance t (calculation relative to immobile Nb) for soil derived from silicate parent materials defined as granite, gneiss and schist at the European continental-scale. Silicate minerals of soil parent materials can be either very resistant to weathering or very soluble and export of elements in dissolved form and precipitation of secondary phases can occur at a large scale. Either way, they leave a strong chemical signature in derived soil, which can be quantified and classified with help of geochemical indices that are useful tools to evaluate chemical weathering trends. Weathering indices and gain-loss mass transfer coefficients were applied to agricultural soil to provide an insight into the weathering processes affecting three silicate parent rocks and their impact on soil development at the European scale. Distinct chemical composition and weathering patterns has been evidenced in silicate derived soil. The interpretation of geographical distribution of soil types with silicate substrate allows better understanding of soil nutritional status, metal enrichments, degradation mechanisms under various climate conditions.

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Continental weathering using combined Hf-Nd isotope system and clay mineralogy: new insights for the Late Cretaceous climate

10.5194/egusphere-egu21-11995 ◽

2021 ◽

Author(s):

Pauline Corentin ◽

Emmanuelle Puceat ◽

Pierre Pellenard ◽

Nicolas Freslon ◽

Michel Guiraud ◽

...

Keyword(s):

Clay Mineral ◽

Late Cretaceous ◽

Chemical Weathering ◽

Clay Mineralogy ◽

Global Scale ◽

Climatic Conditions ◽

Silicate Weathering ◽

Nd Isotope ◽

Continental Weathering ◽

The Impact

The Late Cretaceous period records a pronounced decrease in marine temperatures at a global scale initiating the last greenhouse-icehouse transition, whose origin still remains enigmatic. Continental weathering represents a major sink of atmospheric CO2 through silicate weathering reactions yet the importance of this process in the Late Cretaceous cooling has only been scarcely explored.In this study we explore the impact of the eastern South American margin uplift, concomitant to the long-term Late Cretaceous cooling, on the evolution of chemical weathering of the Brazilian margin, using a new proxy of silicate weathering based on the coupled Lu-Hf and Sm-Nd isotope systems in clays. This proxy, expressed as &#916;&#949;Hf, has been recently calibrated in modern environments (Bayon et al., 2016) but has only been scarcely applied to deep-time environments. This proxy, applied on sediments from DSDP site 356 on the S&#227;o Paulo Plateau, highlights a marked increase in silicate chemical weathering of the southeastern Brazilian margin from the Santonian to the Maastrichtian, also supported by the evolution of the chemical index of alteration (CIA) and clay mineralogy.This increase follows an episode of enhanced mechanical erosion of the margin revealed in the Turonian to Santonian by an increase of primary clay mineral (illite, chlorite) and Ti/Al ratio, linked to the tectonic uplift of the margin. Clay mineral assemblages additionally point to an evolution of local climatic conditions from arid to a more hydrolysing climate following this episode, that we link to a &#8220;rain shadow effect&#8221; affecting the eastern side of the newly formed relief that would have enhanced chemical weathering of the margin.Importantly the temporal coincidence of the increase in chemical weathering depicted here with the marked acceleration of the global cooling recorded worldwide during the Campanian points to a potentially important role of this process on the overall climate decline initiating the descent into our icehouse climate mode. Although records from additional sites are needed to establish the spatial extent of the margin affected by this process, our new dataset brings new insights about the impact of tectonic forcing on climate.Bayon et al. (2016) EPSL 438, p. 25-36.

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Clay Mineralogy and Soil Structure

Advances in Civil and Industrial Engineering - Technology and Practice in Geotechnical Engineering ◽

10.4018/978-1-4666-6505-7.ch002 ◽

2015 ◽

pp. 41-115

Keyword(s):

Plate Tectonics ◽

Chemical Weathering ◽

A Priori ◽

Chemical Properties ◽

Clay Mineralogy ◽

Unconsolidated Sediments ◽

Geological Processes ◽

Soil Structures ◽

Physical And Chemical ◽

Engineering Projects

Most civil engineering projects are built on soil or rock and are constructed solely or partly of these materials. This chapter provides engineers with a good knowledge of the type and characteristics of the terrain on which such projects are to be constructed in order to achieve optimum safety and economic performance. The earth's crust, which is of interest to geotechnical engineers, is made up of rocks and the so-called unconsolidated sediments composed chiefly of solid mineral particles derived primarily from the physical and chemical weathering of rocks. The concepts of plate tectonics and geologic and soil structures are used to explain the geological processes in the earth. Mineralogy is the primary factor controlling the size, shape, and properties of soil particles. It also determines the possible ranges of physical and chemical properties of any given soil; therefore, a priori knowledge of what minerals are in a soil provides intuitive insight as to its behavior.

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STUDY OF CORIANDER SEED OIL (Coriandrum sativum L.)

Science and Technology Development Journal ◽

10.32508/stdj.v13i3.2151 ◽

2010 ◽

Vol 13 (3) ◽

pp. 29-38

Author(s):

Ha Bich Phan ◽

Thach Ngoc Le

Keyword(s):

Biological Activity ◽

Chemical Composition ◽

Essential Oil ◽

Seed Oil ◽

Coriandrum Sativum ◽

Conventional Heating ◽

Geranyl Acetate ◽

Physical And Chemical ◽

Coriander Seed Oil ◽

Coriander Seed

Coriandrum sativum L. belongs to the Apiaceae family, which is cultivated in Dong Nai province, in this paper its seed oil of was studied. The essential oil was extracted by hydrodistillation. We used two methods for activating of hydrodistillation: conventional heating and microwave irradiating. Its physical and chemical indexes were measured. The chemical composition of this oil was identified by GC/MS and quantified by GC/FID. Linalool (75.51-77.21 %), and geranyl acetate (15.64-12.79 %) were the main constituents of the oil which were obtained in 0,32-0.39 % yield. The biological activity of this oil was reported.

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Behavior of Some Varieties in the Kernel Group to the Attack of the Main Pathogens

Annals ”Valahia” University of Targoviste - Agriculture ◽

10.2478/agr-2018-0009 ◽

2018 ◽

Vol 12 (2) ◽

pp. 1-7

Author(s):

Sînziana Venera Morărița

Keyword(s):

Chemical Composition ◽

Climatic Conditions ◽

Complex Chemical ◽

Complex Chemical Composition ◽

Large Production ◽

Special Quality

Abstract Although relatively recent, peach culture has grown great in our country due to the special quality of the fruit, its very complex chemical composition and the large production that can be obtained without much effort. Peach is a species slightly adapted to our climatic conditions, suffers from winter frost, but can provide productive and long productions of 10-15 years.

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