Showing papers on "Clay minerals published in 1982"

The geochemistry of natural waters

Abstract: 1 The Hydrologic Cycle 2 Chemical Background 3 Organic Compounds in Natural Waters 4 The Carbonate System and pH Control 5 Clay Minerals and Ion Exchange 6 Stability Relationships and Silicate Equilibria 7 Kinetics 8 Weathering and Water Chemistry, I: Principles 9 Weathering and Water Chemistry, II: Examples 10 Acid Deposition and Surface Water Chemistry 11 Evaporation and Saline Waters 12 The Oceans 13 Redox Equilibria 14 Redox Conditions in Natural Waters 15 Trace Elements 16 Mathematical and Numerical Models 17 Isotopes Appendices

Spectral evidence for the mineralogy of high‐albedo soils and dust on Mars

Abstract: Because of the lack of direct mineralogic data available for Mars, spectral remote sensing techniques and, in particular, earth-based reflectance spectroscopy remain the primary source of this information. Presented here are laboratory observations which further constrain the mineralogy and origin of the high-albedo soils and dust. Earth-based observations show the reflectance spectra of classical bright regions to be fairly uniform, with a strong Fe3+ → O2− charge transfer absorption edge extending from the near UV through the visible. This absorption is relatively smooth, unlike those observed for crystalline ferric oxides which have superimposed Fe3+ crystal field bands. Dilution of ferric oxide with a spectrally more neutral medium (montmorillonite) weakens the charge transfer and crystal field absorptions together and does not serve to make the ferric oxide spectrum more Mars-like (smoother). Nontronite (ferric-iron-bearing smectite clay) was also investigated for spectral agreement with telescopic observations. Pure nontronite has Fe3+ absorptions analogous to but different from ferric oxides. As in the previous case, the absorptions are very distinct and inappropriate for Mars. Admixture of neither montmorillonite nor ferric oxide serves to improve the nontronite spectrum. The conclusion is that nontronite is not a major component of martian soils, although the presence of other iron-poor clays cannot be totally excluded based on currently available observational data. The best spectral analogs known for high-albedo soil and dust are a specific type of palagonite from Hawaii: X-ray amorphous weathering products of mafic volcanic glass. The indication is therefore that ferric iron on Mars is likely to occur in poorly defined crystallo-graphic sites such as found in these amorphous materials. These materials form slowly under semiarid conditions at ambient temperature. Even low-temperature hydrothermal alteration of glass might provide enough ion mobility to favor some formation of crystalline clays over amorphous gels and may therefore not be the primary mechanism responsible for soil formation on Mars. The amorphous Hawaiian soils exist metastably for thousands of years on Earth. Similar materials on Mars would be expected to survive considerably longer under the present cold and dry climatic conditions.

Double layer theory and compressibility of clays

Abstract: The compressibility of pure clays under external load depends not only on the negative charges and crystallite morphology of clay minerals but also on the ion concentration, cation valency, dielect...

Electrical properties of artificial clay-bearing sandstone

Abstract: Rocks which contain clay minerals often display electrical properties which cannot be predicted by bulk electrical properties of the constituents (Cohen, 1981). Interactions between clay minerals and groundwater can produce polarization phenomena, decreases in resistivity, and supposed nonlinear behavior.

Accumulative phases for heavy metals in limnic sediments

Abstract: Data from mechanical concentrates of recent sediments indicate that clay minerals, clay-rich aggregates and heavy minerals are the major carriers of heavy metals in detrital sediment fractions. Hydrous Fe/Mn oxides and carbonates and sulfides, in their specific environments, are the predominant accumulative phases for heavy metals in autochthonous fractions. Sequential chemical extraction techniques permit the estimation of characteristic heavy metal bonding forms: exchangeable metal cations, easily reducible, moderately reducible, organic and residual metal fractions, whereby both diagenetic processes and the potential availability of toxic compounds can be studied. The data from lakes affected by acid precipitation indicate that zinc, cobalt and nickel are mainly released from the easily reducible sediment fractions and cadmium from organic phases. In contrast at pH 4.4, neither lead nor copper seem to be remobilized to any significant extent. Immobilization by carbonate precipitation seems to provide an effective mechanism for the reduction of dissolved inputs qf metals such as zinc and cadmium in pH-buffered, hard water systems.

Chemistry and clay mineralogy of ando soils, brown forest soils, and podzolic soils formed from recent towada ashes, northeastern japan

Abstract: We conducted chemical and clay mineralogical studies on Ando soils, Brown forest soils, and Podzolic soils that had been formed mainly from felsic Towada-a (1000 B.P.) and Chuseri (4000 B.P.) ashes under different climates and vegetation. Organic carbon accumulated remarkably in the humus horizons of all the soils and contributed to the high CEC of the soils. Soil acidity was observed to be in the order of Ando soils < Brown forest soils < Podzolic soils, reflecting the differences in base saturation and clay mineralogy of these soils, and to have a tendency to decrease with depth within the same profiles. Diagnostic properties of soil samples, such as pH(NaF), phosphate absorption, pyrophosphate-soluble Fe(Fep)/dithionite-citrate-soluble Fe(Fed), pyrophosphate-soluble Al(Alp)/dithionite-citrate-soluble Al(Ald), Fep + Alp/percent clay, Fep + Alp/Fed + Ald, etc., were studied in detail. None of these chemical criteria, however, could distinguish satisfactorily among Ando soils, Brown forest soils, and Podzolic soils formed from Towada ashes. It was noted that both Fep/Fed and Alp/Ald ratios increase with decrease in the soil pH(H2O). Notable differences in clay mineralogy were observed between soil groups. Ando soils had mostly clay fractions dominated by amorphous materials consisting mainly of allophane and imogolite. Nonexpansible chloritized 2:1 mineral, which was major among the crystalline clay minerals, was present in relatively large amounts only in the surface horizons. Brown forest soils showed a diversity in clay mineralogy within the same soil profiles. The clay fractions of the surface soils showed an abundance of chloritized 2:1 mineral with high expansibility and an absence of allophane and imogolite. The subsoils showed major amorphous and paracrystalline materials with minor 2:1 layer silicates. The clay fractions of the Podzolic soils, except those of IIB horizon soils, were characterized by the abundance of chloritized 2:1 mineral varying widely in expansibility and by the absence of allophane and imogolite. The IIB horizons from Chuseri ash had clay fractions dominated by amorphous materials consisting mainly of free iron and alumina. Laminar opaline silica was found in almost all the humus horizons and was relatively abundant in the modern humus horizons of Brown forest soils. We concluded that formation of allophane and imogolite, as well as chloritization of 2:1 layer silicates, is related primarily to soil acidity. Allophane and imogolite formed only in the soils having pH(H2O) >4.9, irrespective of differences in soil groups and soil horizons. The 2:1 layer silicates were considered to have formed largely by alteration of volcanic glass. Chloritization of 2:1 layer silicates was observed to proceed with formation of allophane and imogolite. The formation of laminar opaline silica in the surface soil was considered to be suppressed not only in the Ando soils containing large amounts of allophane and imogolite, but also in the Podzolic soils, which are subject to strong leaching.

Chromium expanded smectite clay

Abstract: Expanded layer, smectite clay having a regular pore structure suitable for catalytic uses and a process for preparing said expanded clay by treating a suspension of commercial smectite clay with a chromium-oligomer solution and subjecting the treated clay to a stabilization heat treatment in an inert gas atmosphere.

Clay mineral diagenesis in Rotliegend aeolian sandstones of the southern North Sea

Abstract: The distribution of diagenetically-formed clay minerals in Rotliegend dune sandstones of the Southern North Sea Basin is closely related to the following factors: (i) the petrography of the sandstones, (ii) the paleoburial depth and tectonic setting of the area, (iii) the thickness of gas-generating Carboniferous strata underlying the Rotliegendes, and (iv) the facies distribution of the overlying Zechstein The diagenetic clay minerals are mainly conversion products of feldspars and, to a lesser extent, of detrital clays and micaceous lithic fragments Sandstones containing dominant drusy illitic and chloritic clay minerals have been buried to depths > 3000 m; if kaolinite is the dominant clay mineral, burial depths were less Sandstones containing feldspars (detrital and authigenic) up to approximately 7% of bulk volume have permeabilities that are about four times higher than sandstones with similar amounts of kaolinite, and as much as 200 times higher than sandstones with similar amounts of illite and/or chlorite

Clay mineralogy of weathering rinds and possible implications concerning the sources of clay minerals in soils

Abstract: Weathering rinds on volcanic clasts in Quaternary deposits in the western United States contain only very fine grained and poorly crystalline clay minerals. Rinds were sampled from soils containing well-developed argillic B horizons in deposits about 105 yr old or more. The clay-size fraction of the rinds is dominated by allophane and iron hydroxy-oxides, whereas the B horizons contain abundant, well-crystallized clay minerals. The contrast between the clay mineralogy of the weathering rinds, in which weathering is isolated from other soil processes, and that of the associated soil matrices suggests a need to reassess assumptions concerning the rates at which clay minerals form and the sources of clay minerals in argillic B horizons. This study suggests that crystalline clay minerals form more slowly in weathering rinds than is generally assumed for soil environments and that the weathering of primary minerals may not be the dominant source of crystalline clay minerals in middle to late Pleistocene soils.

Depositional facies, diagenetic clay minerals and reservoir quality of Rotliegend sediments in the Southern Permian Basin (North Sea); a review

Abstract: The Southern Permian Basin of the North Sea represents an elongate E-W oriented depo-centre along the northern margin of the Variscan Mountains. During Rotliegend times, three roughly parallel facies belts of a Permian desert developed, these following the out- line of the Variscan Mountains. These belts were, from south to north, the wadi facies, the dune and interdune facies, and the sabkha and desert lake facies. The bulk of the gas reservoirs of the Rotliegend occur in the aeolian dune sands. Their recognition, and the study of their geometry, is therefore important in hydrocarbon exploration. Equally important is the understanding of diagenesis, particularly of the diageneticaily-formed clay minerals, because they have an important influence on the reservoir quality of these sands. Clay minerals were introduced to the aeolian sands during or shortly after their deposition in the form of air-borne dust, which later formed thin clay films around the grains. During burial diagenesis, these clay films may have acted as crystallization nuclei for new clay minerals or for the transformation of existing ones. Depending on their crystallographic habit, the clay minerals can seriously affect the effective porosity and permeability of the sands.

The role of clay minerals in influencing porosity and permeability characteristics in the Bridport Sands of Wytch Farm, Dorset

Abstract: The Bridport Sands is a widespread marine sandstone of Lower Jurassic age found in much of southern England. It is a very fine grained, moderately sorted quartz-arenite and is characterized by the alternation of friable and hard calcareous-cemented layers. The sands form the upper reservoir in the Wytch Farm Field, Dorset, which is currently producing at the rate of around 4000 barrels per day. Investigation of core material to assess the suitability of water injection for gas/oil recovery has shown that significant reductions of liquid permeability compared to air permeability occur. These reductions vary from 30% or less in the best quality reservoir to more than 70% in low-permeability sandstones. Clay minerals in the Bridport Sands comprise mainly kaolinite and mixed-layer clays of both the illite-chlorite and illite-smectite types. Small amounts of vermiculite and chlorite also occur. The kaolinite is found as loosely-attached, discrete particles, whilst the mixed-layer clays form patchy pore linings. The permeability reductions may be explained by: (i) the adsorption of water and expansion of poorly-crystalline mixed-layer illite-smectites causing blockage of pore space (this reduction is largely reversible) and (ii) the physical movement of authigenic kaolinite crystal aggregates blocking pore-throats (this reduction is largely non-reversible). The pore-size distribution, clay particle sizes, the distribution of the clays within the pore space, and the composition of the clays are all important factors in controlling porosity/permeability relationships and permeability reductions in the friable reservoir intervals in the Bridport Sands.

Origin of an underclay as revealed by vertical variations in mineralogy and chemistry

Abstract: Regular variations in mineralogy and chemistry indicate that underclay beneath the Herrin (No. 6) coal in southwestern Illinois has undergone in situ alteration. Alteration resulted from the downward movement of hydrogen ions, as indicated by the progressive leaching of acid-sensitive minerals adjacent to the coal. Mineralogical trends observed in the underclay with increasing depth below the coal include: (1) a decrease in the expandability of mixed-layer illite/smectite (I/S); (2) an increase in the amount of ordered US with respect to randomly interstratified US; (3) an increase in the amount of discrete illite with respect to expandable clays; and (4) an increase in chlorite and calcite. Ordered I/S is the dominant mixed-layer clay where calcite is present, but randomly interstratified US dominates where calcite is absent. The pH of the underclay also increases with depth. These trends are consistent with an origin by acid leaching of a preexisting mineral assemblage that included illite, chlorite, and calcite. Other acid-alteration trends may be expected for different precursor minerals and for different leaching intensities and durations.

Clay minerals in the 1980 deposits from Mount St. Helens

Abstract: Phyllosilicates are major components of the <2-µm fraction (1–3 wt. % of most bulk specimens) in more than 50 samples of air-fall tephra from several 1980 eruptions of Mount St. Helens. In all samples, trioctahedral smectite is the major clay mineral. The integral series of 00ℓ reflections in ethylene glycol-treated samples indicates a lack of interstratification; absence of a peak near 5 Å after heat treatment, the 060 peak at 1.54 Å, and energy dispersive chemical analyses indicate that the smectite is a Mg- and Fe- rich, trioctahedral saponite. Minor mica and chlorite are present in the <2-µm fraction of most samples, and some samples show a peak near 12 Å after heating to 550°C which is probably due to the presence of an interstratifled chlorite/collapsed smectite or chlorite/collapsed vermiculite. The tephra contains glass and crystals originating from new magma and lithic fragments incorporated from the pre-existing cone. The clay minerals in the tephra are lithic components stripped from older, hydrothermally altered rocks during explosive ejection. Cleaned pumice fragments, which are new magmatic components, lack smectite, but contain rare biotite in xenoliths. Old, hydrothermally altered rocks from the volcano’s summit and from the debris-avalanche (former north flank) contain saponite together with chlorite and chlorite/smectite which may have formed from it. Saponite and zeolites that precipitated from neutral to alkaline hydrothermal solutions line cavities in some of these rocks. The saponite was probably not subjected to magmatic temperatures because heating this material for 5 min at 750°C collapses it irreversibly to 10 Å. Kaolinite, alunite, and opal, indicative of acid-sulfate alteration, were found only in the pre-1980 summit crater and the southwest thermal area, but were not evident in the lithic components of the 1980 deposits.РезюмеФиллосиликаты являются главными компонентами фракции размером <2 μM (1–3 весового % большинства основных типов) в более, чем 50 образцах из воздушно-осадочных тефр, изверженных при нескольких взрывах вулкана Горы Святой Елены в 1980 году. Трехоктаэдрический смектит является главным глинистым минералом во всех образцах. Полная серия отражений 00ℓ образцов после обработки в этиленовом гликоле указывает на отсутствие внутринапластования; отсутствие пика в поблизости 5 А после нагрева и присутствие пика 060 при 1,54 А, а также дисперсный химический анализ указывают на то, что этот смектит является Мg- и Ре-богатым трехоктаэдкическим сапонитом. Незначительные количества слюды и хлорита присутствуют во фракции размером <2 μм в большинстве образцов, и некоторые образцы имеют пик в поблизости 12 А после нагрева до 550°С, что, вероятно, связано с присутствием внутринапластованных хлоритов/опавших смектитов или хлоритов/опавших вермикулитов. Тефра содержит стекло и кристаллы, происходящие из новой магмы и литовых фрагментов из прежде существующего конуса. Глинистые минералы в вулканическом пепеле являются литовыми компонентами отделенными от древнейших пород, гидротермально измененных во время взрывов. Чистые фрагменты пемзы, которые являются новыми матовыми компонентами, не содержат смектит, но содержат редкий биотит в ксенолитах. Древние, гидротермально измененные породы из пика вулкана и из лавин (прежняя северняя сторона) содержат сапонит вместе с хлоритом и хлоритом/смектитом, которые могут образоваться из этих пород. Сапонит и цеолиты, которые осаждались от нейтральных до щелочных гидротермальных растворов залегают щели некоторых из этих пород. Вероятно, сапонит не подвергается магмовым температурам, потому что нагрев этого материала в течение 5 минут при 750°С изменяет его необратимо в 10 А минерал. Каолинит, алюнит, и опал, указывающие на присутствие кислотно-сульфатных изменений, были найдены только в кратере из извержаний перед 1980 годом и в южно-западной термической области, но не присутствовали в литовых компонентах осадков 1980 года. [Е.С.]ResümeePhyllosilikate sind die Hauptbestandteile der Fraktion <2 µm (1–3 Gew.-% der meisten Durchschnittsproben) in den mehr als 50 Tephraproben von mehreren Eruptionen des Mount St. Helens des Jahres 1980. In allen Proben ist ein trioktaedrischer Smektit das häufigste Tonmineral. Die Basis-Reflexe bei mit Äthylenglycol-behandelten Proben deuten darauf hin, daß keine Wechsellagerung vorhanden ist; das Fehlen eines Peaks bei 5 Å nach dem Erhitzen, der 060-Peak bei 1,54 Å und energiedispersive chemische Analysen zeigen, daß der Smektit ein Mg- und Fe-reicher, trioktaedrischer Saponit ist. Geringe Gehalte an Glimmer und Chlorit sind in den Fraktionen <2 µm der meisten Proben vorhanden. Einige Proben zeigen nach dem Erhitzen auf 550°C einen Peak bei 12 Å, der wahrscheinlich von einer Wechsellagerung Chlorit/kontrahierter Smektit oder Chlorit/kontrahierter Vermiculit herrührt. Die Tephraproben enthalten Glas und Kristalle, die vom neuen Magma stammen und Gesteinsbruchstücke die vom vorherigen Vulkankegel stammen. Die Tonminerale in den Tephraproben sind Gesteinsbestandteile, die von alten, hydrothermal veränderten Gesteinen stammen und wäharend des Ausbruches aufgenommen wurden. Frische Bimsfragmente, die neue magmatische Komponenten sind, enthalten keinen Smektit, doch enthalten sie etwas Biotit und Xenolithe. Alte, hydrothermal veränderte Gesteine vom Vulkangipfel und vonder Schuttlawine (ehemalige Nordflanke) enthalten Saponit zusammen mit Chlorit und Chlorit/Smektit, die sich daraus gebildet haben könnten. Saponit und Zeotithe, die aus neutralen bis alkalischen hydrothermalen Lösungen ausgefallen sind, treten in manchen dieser Gesteine als Hohlraumauskleidungen auf. Der Saponit kam wahrscheinlich nicht unter magmatische Temperaturen, da ein Erhitzen dieses Minerals auf 750°C für 5 Minuten zu einer irreversiblen Kontraktion auf 10 Å führt. Kaolinit, Alunit, und Opal, Indikatoren für eine Sulfat-saure Umwandlung, wurden nur im Gipfelkrater von vor 1980 und in den südwestlichen thermalen Gebieten gefunden, traten aber nicht als Gesteinsbestandteile der Ablagerungen von 1980 auf. [U.W.]RésuméDes phyllosilicates sont les composés majeurs de la fraction <2 µm (1–3% par poids de la plupart des échantillons en masse) dans plus de 50 échantillons de tephres tombant de l’air de plusieurs éruptions de 1980 du Mont St. Hélène. Dans tous les échantillons, la smectite trioctaèdrale est le minéral majeur. Les séries intégrales de reflections 00ℓ d’échantillons traités au glycol éthylène indiquent un manque d’interstratification; l’absence d’un sommet près de 5 Å après un traitement à la chaleur, le sommet 060 à 1,54 Å, et des analyses chimiques dispersant l’énergie indiquent que la smectite est une saponite trioctaèdrale riche en Mg et en Fe. Du mica et de la chlorite mineurs sont pérsents dans la fraction <2 µm de la plupart des échantillons, et quelques échantillons montrent un sommet près de 12 Å après échauffement à 550°C, ce qui est probablement dû à la présence d’une chlorite interstratifiée/smectite effondrée ou d’une chlorite/vermiculite effondrée. Les tephres contiennent du verre et des cristaux provenant de magma nouveau et des fragments tithiques incorporés du cone pré-existant. Les minéraux argileux dans les tephres sont des composés lithiques arrachés pendant l’éjection explosive de roches plus anciennes hydrothermalement alterées. Des fragments de pumice nettoyés, qui sont des composées magmatiques nouveaux, manquent de smectite, mais contiennent de la biotite rare dans les xénolithes. D’anciennes roches hydrothermalement alterées du sommet du volcan et de l’avalanche-débris (précédemment la côte nord) contiennent de la saponite ainsi que de la chlorite/smectite qui pourraient s’être formées à partir de cette première. Des saponites et des zéolites qui avaient précipitée de solutions hydrothermales neutres à alkalines recouvrent les cavités de certaines de ces roches. La saponite n’a probablement pas été soumise à des températures magmatiques puisqu’échauffer ce matériau pendant 5 min. à 750°C l’effondre irréversiblement à 10 Å. La kaolinite, l’alunite, l’opale, indiquant une altération sulphate-acide, n’ont été trouvées que dans le cratère pré-1980 et la région thermale du sud-ouest, mais n’étaient pas évidentes dans les composés lithiques des depôts de 1980. [D.J.]

Influence of Soil Moisture on Smectite Formation in Soils Derived from Serpentinite

Abstract: X-ray diffraction (XRD), differential thermal analysis (DTA), and transmission electron microscopy (TEM) were used to characterize the phyllosilicates in a catena of soils derived from serpentinite in southwestern Oregon. Serpentine (variety chrysotile) and chlorite were the phyllosilicates in the bedrock and in the <2-µm fraction of soil samples from the two well-drained profiles. Samples from the two soils which were deeper, finer-textured, and more poorly drained consisted of smectite, serpentine, and chlorite. The data indicate that smectite is forming from serpentine and/or chlorite in poorly drained landscape positions. The abundance of amorphous material, revealed by TEM, may suggest a mechanism for smectite formation in these soils.

Sediment Fractionation of Cu, Ni, Zn, Cr, Mn, and Fe in One Experimental and Three Natural Marshes

Abstract: Dredged sediments from the Gulf Intracoastal Waterway near Galveston, Tex., were used as a substrate material in the construction of an experimental intertidal salt marsh. Selected substrate properties were compared with those of established marshes. Clay mineralogical properties of the experimental marsh were compared with those of three nearby natural marshes. A sequential chemical extraction procedure was used to obtain data on the partitioning of micronutrients and heavy metals among selected marsh substrate fractions. Clay minerals found in the sediments of the experimental marsh were equivalent to those identified in the natural marshes. Total elemental substrate concentrations of Cu, Ni, Cr, Zn, Mn, and Fe averaged 7.9, 8.6, 25.5, 25.2, 123, and 12,200 ..mu..g/g, respectively, over the four marsh sites. Copper, nickel, zinc, and chromium displayed only minor variations in substrate partitioning between the experimental and natural marsh samples. Micronutrients and heavy metal concentrations in the exchangeable and water-soluble fraction were low compared with other fractions. Approximately 30% of the total substrate Cu, Ni, and Zn was associated with the organic matter fraction. Metals fixed within the lattice structures of clay and silicate minerals ranged from 20% Mn for experimental marsh samples to 90% Cr for one of the naturalmore » marshes. Major differences in Mn and Fe substrate partitioning were observed when the experimental marsh samples were compared with those of the natural marshes.« less

Clay minerals in Northern Plains coal overburden as measured by X-ray diffraction

Abstract: Mathematical models were tested for changing x-ray diffraction data to percentages of clay minerals in coal overburden. Various factors for adjusting peak areas were tested on 50 eastern Montana samples that contained smectite, illite, and daloinite, with lesser amounts of other minerals. Cation exchange capacities (CEC) of the clays were estimated from the calculated mineral percentages and correlated against measured CEC. The best model gave in r/sup 2/ of 0.89. It was used for estimating clay mineralogy at six mine sites in the Northern Great Plains. Average mineral contents in the surface 8 to 38 m of five of seven drill holes in the Montana-Wyoming border area were 40% smectite, with 20% each of illite and kaolinite. Clays from greater depths in the same area had no smectite and an average of 50% each of illite and kaolinite. All samples from a mine in central North Dakota were high in swelling clay, with an average of 60% smectite and 10% vermiculite.Samples from four holes at a mine in eastern Wyoming were all high in kaolinite, having an average of 50% with 30% illite and 10% interstratified smectite-vermiculite.

Migration of Alkaline Pulses in Reservoir Sands

Abstract: Establishing the amount of alkali loss by rock reactions is critical because successful application of most alkaline flooding techniques requires that hydroxide propagate through a large portion of the reservoir. This paper presents a mathematical analysis of the chromatographic movement of alkaline pulses when they are scaled to reservoir flow rates and distances. Using only this analysis and laboratory data, the authors show how to estimate the distance an alkaline pulse traverses under field conditions before its concentration diminishes to ineffective levels. Laboratory core tests and X-ray analyses identify the various mineral reactions and their rates. For clayey sands a fast, reversible, sodium/hydrogen ion exchange retards alkali concentration velocities. Fine silica and quartz are suggested as important dissolving minerals, with slower-dissolving clays and clay minerals releasing soluble aluminum, which may redeposit with soluble silica as new aluminosilicate minerals. While new mineral formation influences the aqueous aluminum and silica concentrations, hydroxide consumption appears to be controlled mainly by the dissolution reaction. Firstorder kinetics most closely represent the dissolution behavior; lumped-parameter rate constants are reported for Huntington Beach and Wilmington sands and for a Berea sandstone.

The interactions of humic compounds with electrolytes and three clay minerals under simulated estuarine conditions

Abstract: Laboratory studies of the reactions between dissolved humic substances and dissolved sodium, magnesium, calcium, iron and aluminium are described together with studies of the adsorption of humic substances onto the clay minerals illite, kaolinite and montmorillonite under simulated estuarine conditions. It is demonstrated that only minor quantities of humic substances are precipitated in the presence of Na, Mg and Ca up to ca. 1.5 times their seawater concentrations. The total amount of humic substance precipitated is dependent on the cation present and increases in the order Na

Palaeosols of the Lower Jurassic Mishhor and Ardon Formations (‘Laterite Derivative Facies’), Makhtesh Ramon, Israel

Abstract: The Lower Jurassic sequence exposed at Makhtesh Ramon, in the south-western Negev of Israel, comprises cyclic fluviatile sediments derived almost exclusively from the reworking of an older laterite terrain A succession of palaeosols, having the characteristics of modern, red-brown earths, has developed during periods of sub-aerial exposure upon the fine grained overbank sediments A marked seasonal palaeoclimate with accompanying poor sub-surface drainage conditions, and some stagnation of ground water, is reflected by the distribution and mottling patterns of the iron minerals (with varying degrees of hydration), precipitation of illuviated carbonate and sulphate minerals and the development of soil microrelief A complex history of pedogenesis and ground water alteration is shown by the rapid lateral facies change within this sequence, into one dominated by high-alumina flint clay and bauxite Relict pedogenetic and sedimentological textural features of the combined palaeosol/fluviatile sequence, have been identified and mapped within the flint clay/bauxite lithologies These features include irregular voids, produced by solution of pedogenic sulphate nodules, slickensided curviplanar surfaces of soil microrelief, and depositional bedding The field relationships of these relicts indicate the overprinting of a younger, chemical weathering event giving rise to the high-alumina flint clay and bauxites The geometric shape of the upper bounding surface of the ‘bauxite’ alteration zone, is irregular and has an ‘intrusive’ character with respect to the younger, overlying, unaltered sediments This, together with abrupt changes in mottling patterns near the contact zone and subtle changes in mineralogy from a bauxitic assemblage at depth to one containing mixed-layer clay minerals and carbonates nearer the contact, leads to the conclusion that the later stages of chemical weathering occurred within a confined system, where ground water movements were induced by intake of underlying aquifers

Contents of natural radioactive nuclides in soil in relation to their surface area

Abstract: Concentrations of uranium series nuclides (238U, 226Ra, 210Pb), thorium series nuclides (228Ra, 212Bi), and potassium in soil of a granitic belt were examined in relation to their surface area of soil, clay mineral composition, and the SiO2 and Fe contents. In soil which is less weathered and has a surface area of around 10 m2/g, the 238U, 226Ra, 210Pb, 228Ra, and 40K contents increase with an increase the SiO2 content related to the elemental compositions of their parents rocks. In homologous soils resulting from progressive weathering, the 238U, 226Ra, 210Pb, and 228Ra contents are found to increase with increasing surface area. For an homologous soil which is free from the clay consisting of three-layer units, the 40K content decrease with increasing surface area. However, in an homologous soil which contains a clay consisting of three-layer units, the 40K content is not surface area dependent.

Chemical and mineralogical properties of sandy and loamy‐sandy ochreous brown earths in relation to incipient podzolization in a brown earth—podzol evolutive sequence

Abstract: Summary Chemical and mineralogical properties of ochreous brown earths have been studied with particular reference to: (1) the distribution within the profiles of Fe and Al compounds; (2) the occurrence of smectite-like clay minerals in surface horizons. Ochreous brown earths studied belong to a developmental sequence of forest soils, from acid brown earths to ferric podzols, developed on sandy or loamy-sandy acid parent materials. In such a soil sequence, both selective chemical and mineralogical data show clearly that podzolization is already active in ochreous brown earths, whereas such an incipient podzolization is quite undetectable by direct morphological observations. The distribution patterns of amorphous Fe and Al hydrous oxides and organic associations, clearly show the intergrade character of ochreous brown earths, when compared with the vertical distribution of Fe and Al forms in acid brown earths and podzolized soils. The Fe/Al ratio of both an NH4-oxalate extract and an NaOH/Na-tetraborate extract buffered at pH 9.7, measured in the A1B diagnostic horizon of ochreous brown earths, is a particularly appropriate and useful genetic criterion for the detection of incipient podzolization. Moreover, the presence of expansible clay minerals (degradation smectites) in the clay-sized fraction of the surface horizons of ochreous brown earths (A1 and A1B) can be considered as supplementary evidence of incipient podzolization.

Volumes, Types, and Distribution of Clay Minerals in Reservoir Rocks Based on Well Logs

Abstract: Discussed in this paper, is an innovative digital shaly sand evaluation approach which provides information on total and effective reservoir porosity, total and effective fluid distribution based on the Waxman-Smits equation, reservoir productivity, silt volume, and volumes, types and distribution modes of clay minerals present in subsurface ford. 52 refs.