Showing papers on "Clay minerals published in 1986"

The occurrence of interlayer clay-organic complexes in two New Zealand soils

Abstract: By using x-ray diffractometry and /sup 13/C-NMR spectroscopy, in combination with chemical and heat pretreatments, the authors have found good evidence for the occurrence of interlayer clay-organic complexes in two New Zealand soils. Here, the clay mineral is a regularly interstratified mica-smectite, and the organic species is a humic substance with a polymethylene chain structure. The organic material in the complex is resistant to peroxidation and pyrophosphate extraction. It is also thermally stable, being extensively decomposed only after the complex is heated at 400/sup 0/C. A combination of soil factors seems necessary for interlayer complex formation. This includes a smectitic clay mineralogy, an accumulation of organic matter associated with a low microbial activity, and a highly acid soil reaction.

Kinetics of Ionic Reactions in Clay Minerals and Soils

Abstract: Publisher Summary This chapter discusses the principles of kinetics to clay minerals and soils and reviews present literature dealing with the kinetics of elemental reactions in these systems. Chemical kinetics deal with chemical reaction rates and these rates are explained in the chapter in terms of reaction mechanisms. There are two salient reasons for studying the rates of chemical reactions: first to predict how quickly a reaction mixture moves to its equilibrium state, and to reveal reaction mechanisms. One should realize that the rate law is determined by experimentation and it cannot be inferred by simply examining the overall chemical reaction equation. A number of equations have been employed to describe the kinetics of reactions in clay minerals and soils. These have included the first-order, Elovich, parabolic diffusion, zero–order, second–order, and two–constant rate equations. Data based on the kinetics of ion exchange in pure clay systems is used by soil chemists for many years to model kinetic reactions in heterogeneous soil systems. Vermiculite, montmorillonite, kaolinite, and hydrous mica vary drastically in their preferences, in ion binding affinities, and in types of ion exchange reactions. Soil systems are typically composed of complex mixtures of clay minerals, noncrystalline components, oxides, hydroxides, and organic matter. The inevitable interaction of these various components creates a heterogeneous exchange complex that makes the kinetics of ionic exchange in these systems difficult to study.

The engineering geology of clay minerals: swelling, shrinking and mudrock breakdown

Abstract: A B S T RA C T: Swelling, shrinking and physical breakdown processes are reviewed with reference to well-known mudrock and overconsolidated clay formations in the UK and USA. Swelling results from two processes: the equilibration of depressed porewater pressures following stress relief, and the physico-chemical (osmotic) response of component clay minerals. Expansion in Na-smectite, and to a lesser extent Ca-smectite, clays is governed by double-layer swelling, whereas in kaolinites it is purely a mechanical unloading phenomenon; illites show an intermediate response. Intraparticle swelling in mudrocks older than the Silurian in the UK, or Upper Mississippian in the USA, can be expected to be reduced because of the removal of expandable layers by burial diagenesis. Shrinkage, like mudrock breakdown, is restricted to the partly saturated zone. Suction pressure-moisture content curves of indurated mudrocks are shown to be different from mudrocks and clays with high proportions of expandable clay minerals. Classification of expansion potential based on activity ratio poses problems with indurated types, but with some modification of method reasonable predictions can be made. Controls on physical disintegration are identified as: (i) incidence of sedimentary structures and discontinuities, (ii) slaking (air breakage), (iii) expandable clay mineral content, especially smectite, and (iv) clay mineral fabric orientation. Exceptionally high exchangeable sodium percentages have been measured in Coal Measures rocks susceptible to breakdown. Clay soils susceptible to significant volume change occupy about 20% of the USA land surface and the annuat damage to property is regarded by some as being of naturaI disaster proportions. Indeed the bill for man-made structures was estimated by Holtz (1983) to be about $6 billion per annum at 1982 prices. Driscoll (1983) considered that the scale of the problem is less in the UK because of the mild, damp climate. Nevertheless, the shrinkage of heavy clays (from Lias to London Clay) in east and southeast England is particularly severe in drought years. These ground movements are influenced by the transpiration of broadleaf trees and between 1971-80 the damage cost to dwellings resulting from this type of 'subsidence' was estimated by Reece (1980) to be about s million. Most of this cost can

Sorption and desorption of cobalt by soils and soil components

Abstract: SUMMARY The sorption of Co by individual soil components was studied at solution Co concentrations that were within the range found in natural soil solutions. Soil-derived oxide materials sorbed by far the greatest amounts of Co although substantial amounts were also sorbed by organic materials (humic and fulvic acids). Clay minerals and non-pedogenic iron and manganese oxides sorbed relatively little Co. It is considered that clay minerals are unlikely to have a significant influence on the sorption of Co by whole soils. Cobalt sorbed by soil oxide material was not readily desorbed back into solution and, in addition, rapidly became non-isotopically exchangeable with solution Co. In contrast, Co was relatively easily desorbed from humic acid and a large proportion of the Co sorbed by humic acid remained isotopically exchangeable. Cobalt sorbed by montmorillonite was more easily desorbed than that sorbed by soil oxide but less easily than that sorbed by humic acid. Cobalt sorption isotherms for whole soils at low site coverage were essentially linear and the gradients of isotherms increased with pH. A comparison of isotherm gradients for whole soils and individual soil components supported the suggestion that Co sorption in whole soils is largely controlled by soil oxide materials.

Boron Adsorption and Silicon Release by the Clay Minerals Kaolinite, Montmorillonite, and Illite

Abstract: Boron adsorption behavior on the clay minerals kaolinite, montmorillonite, and illite was investigated. Adsorption increased at low pH, exhibited a peak in the pH range 8 to 10, and decreased at high pH. It was assumed that B adsorbs by means of a ligand exchange mechanism with aluminol groups at the edges of the clay particles. The constant capacitance model was able to describe B adsorption on kaolinites over the entire pH range studied (3-12), using only one adjustable parameter: the boron surface complexation constant. The model was able to fit B adsorption on montmorillonites and illites using three adjustable parameters; however, the chemical significance of some of the surface complexation constants is uncertain. Silicon release to solution increased in the order: kaolinite « illite < montmorillonite and exhibited a minimum in the pH range 8 to 9. Boron adsorption on kaolinites was reduced only slightly in the presence of added silicate despite considerable silicate adsorption. Boron adsorption on montmorillonites was unaffected by the presence of added silicate. It is suggested that B and silicate adsorb on specific sites and that little anion competition occurs. Additional Index Words: anion adsorption, ligand exchange, silicate adsorption, surface chemistry, constant capacitance model. Goldberg, S., and R.A. Glaubig. 1986. Boron adsorption and silicon release by the clay minerals kaolinite, montmorillonite, and illite. Soil Sci. Soc. Am. J. 50:1442-1448. B is AN ESSENTIAL ELEMENT in plant nutrition being required in low concentrations for sufficiency and producing toxicity symptoms and marked yield decrement at higher concentrations. Since the concentration range between deficiency and toxicity for B is narrow, reactions which may govern its availability are of interest. Analyses of B sorptipn behavior in whole soils have indicated that clay minerals play an important role. Elrashidi and O'Connor (1982) found that clay content was significantly correlated with adsorbed B of ten soils from New Mexico. Wild and Mazaheri (1979) studied two soils from the Reading Univ. farms in Britain and found that the loamy clay soil adsorbed more than four times as much B on a per gram basis as the sandy loam soil. 1 Contribution from the U. S. Salinity Laboratory, USDA-ARS, 4500 Glenwood Drive, Riverside, CA 92501. Received 21 Aug. 1985. 2 Soil Scientist and Biological Laboratory Technician-Soils, respectively. The adsorption behavior of B on various layer silicate clay minerals has been investigated previously (Scharrer et al., 1956; Harder, 1961; Kingston, 1964; Fleet, 1965; Sims and Bingham, 1967;Porrenga, 1967; Couch and Grim, 1968; Singh, 1971; Jasmund and Lindner, 1973; Keren et al., 1981; Keren and Mezuman, 1981). Several researchers have studied and compared the B adsorption characteristics of illite, montmorillonite, and kaolinite under conditions of short (<24 h) contact time (Scharrer et al., 1956; Kingston, 1964; Keren and Mezuman, 1981). The three minerals exhibited increasing B adsorption with increasing pH. Adsorption peaks occurred at pH 8.5 to 10 and were followed by a gradual decline. In all three studies the order of boron adsorption on a per gram basis was: kaolinite < montmorillonite < illite. In contrast, Sims and Bingham (1967) found B adsorption on kaolinite to be much greater than on montmorillonite. They attributed this order of reactivity to the fact that the montmorillonite sample had been washed free of Fe and Al impurities while the kaolinite sample had not. Kingston (1964) was able to describe his adsorption isotherms at dilute concentrations using the Langmuir equation. Singh (1971) represented his B adsorption data on kaolinite and montmorillonite by both the Langmuir and the Freundlich equations. He found, however, that the fit of the Freundlich equation was closer to the experimental data over a wider range of solution B concentration. Experiments investigating B sorption behavior under conditions of long term contact (28-180 d) have also been conducted (Harder, 1961; Fleet, 1965; Couch and Grim, 1968; Jasmund and Lindner, 1973). In these studies the order of magnitude for boron adsorption was the same as in the short term studies: kaolinite < montmorillonite < illite. Harder (1961) found that, unlike the adsorption on kaolinite and montmorillonite, B adsorption on a clay sample containing both illite and chlorite was not readily reversible by washing with distilled water. In order to explain this behavior, he suggested that B had become incorporated into the illite and chlorite lattices by substituting for tetrahedral Si and Al ions. Fleet (1965) suggested that B is initially chemisorbed onto illite particles and subsequently incorporated into the tetrahedral sites. Couch and Grim (1968) concurred with this mechanism, suggesting that B adsorbs as B(OH)^ on the particle edges GOLDBERG & GLAUBIG: BORON ADSORPTION AND SILICON RELEASE 1443 and migrates by intracrystalline diffusion into tetrahedral sites where it replaces structural Si and Al. Jasmund and Lindner (1973) found that B adsorption on kaolinite and montmorillonite particles, as well as on illite particles increased even after 180 d of reaction time. For this reason, they suggested that B uptake by all three minerals was governed by the same adsorption mechanism. Jasmund and Lindner (1973) synthesized B containing kaolinite, montmorillonite, and illite materials and studied the coordination of B in these mineral lattices. Using photoelectron spectroscopy (ESCA) and infrared spectroscopy, they found evidence for 4-fold coordination of B in the synthetic illite and montmorillonite. Since no such evidence was found for the B in the synthetic kaolinite, Jasmund and Lindner (1973) concluded that B substitutes for tetrahedral Al and not for tetrahedral Si. One of the limitations of the Langmuir and Freundlich isotherms is their inability to describe adsorption behavior over changing conditions of solution pH. A phenomenological equation was developed by Keren et al. (1981) which includes the pH variable in describing adsorption. Keren and Mezuman (1981) used the phenomenological equation to fit B adsorption on kaolinite, montmorillonite, and illite at several pH values using the same set of constants: KHB, KB, KOH, and the total B adsorption capacity factor, T. Keren et al. (1981) were not able to show any physical significance of the absolute values of the constants KHB, KB, and KOH. Keren and Mezuman (1981) calculated B adsorption per unit of total surface area. They found that on this basis, as well as on a per gram basis, adsorption on illite much exceeded adsorption on montmorillonite, despite the greater surface area of the latter. From these results, Keren and Talpaz (1984) concluded that B adsorption occurred on the broken edges of clay minerals. These authors also suggested that B is adsorbed via a ligand exchange mechanism with surface hydroxyl groups on the clay edges. Ligand exchange with hydroxyl groups has been invoked as the mechanism of B adsorption on Al and Fe oxide minerals (Sims and Bingham, 1968; McPhail et al., 1972). Boron adsorption on oxide minerals has been observed to produce shifts in the point of zero charge (PZC) of Al and Fe oxide minerals (Fricke and Leonhardt, 1950; Alwitt, 1972; Beyrouty et al., 1984; Blesa et al., 1984). This behavior indicates specific adsorption of B on these materials. The constant capacitance model (Stumm et al., 1970; Schindler and Gamsjager, 1972; Stumm et al., 1976; Stumm et al., 1980) uses a ligand exchange mechanism to describe adsorption and includes the pH variable. It is a chemical model in that it defines surface species and chemical reactions explicitly. The constant capacitance model has been used successfully to describe B adsorption on four Al and three Fe oxide minerals under changing conditions of solution pH (Goldberg and Glaubig, 1985). Silicate adsorption has been observed to produce shifts in the PZC of the Fe oxide mineral goethite (Kingston et al., 1972; Sigjg and Stumm, 1981), again indicating specific adsorption. The clay minerals muscovite (McKeague and Cline, 1963), kaolinite, and montmorillonite (Beckwith and Reeve, 1964) have been observed to release silicate to aqueous solution. Beckwith and Reeve (1964) found that silicate release from both kaolinite and montmorillonite was lowest in the intermediate pH range. However, below pH 7.5 much greater amounts of silicate were released from montmorillonite than from kaolinite, indicating a much lower stability of the former. By studying silicate release as a function of time, Beckwith and Reeve (1964) observed that initial silicate release from montmorillonite was rapid and was followed by a more gradual increase in solution concentration. They suggested that this initial release rate was too high to result from dissolution of the mineral. Beckwith and Reeve (1964) therefore postulated that the initial silicate concentrations had been present in sorbed form on montmorillonite in its natural environment. Beckwith and Reeve (1963) showed that kaolinite and montmorillonite have the ability to adsorb silicate from solution at pH values >7. The authors felt, however, that the adsorption range might not have been delineated due to considerable release of silicate. McPhail et al. (1972) found that amorphous Al and Fe oxides which had previously adsorbed silicate exhibited a decrease in their B adsorption capacity. This decrease was progressive with the amount of silicate adsorbed by the materials. McPhail et al. (1972) suggested that both anions adsorb via a ligand exchange mechanism with the same set of hydroxyl groups. Prior adsorption of silicate had thus inactivated many of the B adsorbing sites. Bingham and Page (1971) studied the effect of silicate pretreatment on the B adsorption properties of an allophanic soil. They found that adsorption of silicate even up to four times the amount of B adsorption aff

Quantitative mineralogical analysis of some bangladesh soils with x-ray, ion exchange and selective dissolution techniques

Abstract: A B S T R A C T: Fine clay, coarse clay, and silt fractions of four Bangladesh soils were studied using XRD, ion exchange, and selective dissolution techniques. Constants for the XRD intensity-weight proportion relationships were derived using these techniques. Smectite and mica were found to be dominant in Batra and Ghior soils, whereas kaolinite and mica were dominant in the Naraibag and Ghatail soils. Other minerals present were vermiculite, vermiculite with hydroxyaluminium interlayers, chlorite, randomly interstratified chlorite-mica, feldspar, quartz, and trace amounts of amphibole. The amorphous material content varied between 1 and 11% and decreased with increasing particle size. No crystalline iron oxides were detected in untreated clay fractions. Many methods are available for the quantitative mineralogical analysis of soils: these include X-ray diffraction, differential thermal analysis, differential thermogravimetric analysis, microscopic analysis, selective dissolution and ion exchange. While each of these methods can give satisfactory results for mixtures of pure and well-crystallized components, considerable problems may arise in the quantitative mineralogical analysis of soils and sediments. Some of these problems are: occurrence of amorphous substances, deviations from 'ideal' chemical composition, variations in X-ray order/crystallinity and particle size, and occurrence of mixed-layer minerals. XRD is probably the best individual method for quantitative mineralogical analysis. However, the above problems are inherent in the method, and major difficulties are encountered in the determination of the true relationship between XRD intensities and weight proportions of the minerals in soils and sediments. There are two methods for determining this relationship, one using standard mineral mixtures and the other by determining the mineralogical composition of representative samples by independent methods and then calculating the intensity-weight proportion relationship. Alexander & Klug (1948) and K!ug & Alexander (1974) showed that the X-ray intensity reflected by a component P in a mixture is related to the volume proportion vp by the equation

Multiple cation-exchange capacity measurements on standard clays using a commercial mechanical extractor

Abstract: Sequential cation-exchange capacity (CEC) measurements were obtained from standard clays using a mechanized, variable-rate leaching device. The device consists of a motorized screwjack and as many as 24 leaching tubes coupled to 60-ml plastic syringes. Controlled withdrawal of the syringe plungers produces a vacuum that permits samples in the leaching tubes to be extracted at a uniform rate. A single, 8-hr leaching of clays with 35 ml of salt solution was found to be comparable to multiple saturations or displacements using a centrifuge. CECs consistent with published values were obtained for reference 2:1 clay minerals using both acetate and chloride salts of Na, Ca, and Mg. Potassium-exchange capacities were also successfully measured following in situ thermal treatment of samples in the leaching tubes. Variations in measured CECs for kaolin-group minerals due to salt intercalation were minimized by using chloride rather than acetate salts and by washing with a dilute aqueous solution of the saturating cation following initial saturation. The mechanical extractor significantly reduced the effort required to perform conventional CEC determinations without sacrificing analytical precision.

The Nature of Vermiculite in Adirondack Soils and Till

Abstract: The clay and bulk mineralogy of soil and till from 26 Adirondack watersheds was studied. The materials consist typically of quartz, K-feldspar, plagioclase, mica, vermiculite, and kaolinite. Talc, smectite, halloysite, and hornblende are present in some samples. The clay fraction of the soils is composed predominantly of vermiculite, likely derived from the transformation of a mica precursor, and kaolinite. The soil vermiculite commonly contains hydroxy-Al interlayers which are especially prevalent in the B-horizon samples. Despite significant variation in the type of bedrock and the composition of heavy mineral assemblages in these watersheds, the clay mineralogy is remarkably uniform. This finding supports earlier suggestions that the occurrence of vermiculite in soils is more dependent on climate than on the nature of the parent material.

Packing material for liquid chromatography

Abstract: A packing material for liquid chromatography, comprising a spherical clay mineral powder which comprises a naturally occurring or synthetic water-swellable clay mineral, a clay mineral having foreign cations substantially substituted for interlayer ions inherently present in the naturally occurring or synthetic water-swellable clay mineral, or a calcined product thereof.

Mineral weathering processes in podzolic soils on granitic materials and their implications for surface water acidification

Abstract: Many areas where concern has arisen over the recent acidification of their surface waters contain podzolic soils developed upon granitic materials. The mineral weathering processes in these soils are reviewed and the ways in which such processes could be altered by acid deposition are considered. The most weatherable primary minerals are plagioclase feldspar, biotite and fine-grained dioctahedral mica and their decomposition, which is mediated by organic acids, leads to the formation of proto-imogolite allophane, vermiculite and smectite. Other clay minerals occurring in podzols such as kaolinite and halloysite, as well as gibbsite, are probably inherited from previous weathering cycles, although a present-day pedogenic origin should not be ruled out entirely. The possibility is considered that the partial replacement of soil organic acids by mineral acids introduced through precipitation could bring about significant differences in mineral weathering, leading to more acid soils with more dissolved ionic aluminium in soil and stream waters. The weathering products involved in the mobilization of aluminium from podzols are likely to be proto-imogolite allophane and hydroxy Al-interlayered vermiculite or smectite. Another possibility is that sand and silt-sized plagioclase feldspars are more reactive than previously realized.

Geologic occurrence of zeolites and some associated minerals

Abstract: The principal geologic settings of zeolites are (1) saline, alkaline lakes, (2) saline, alkaline soils, (3) deep-sea sediments, (4) low-temperature open hydrologic systems, (5) burial diagenesis, and (6) hydrothermal-geothermal systems. Volcanic ash layers alter rapidly to zeolites in saline, alkaline lakes, and relatively pure deposits can be formed. Silicic volcanic glass is altered slowly, and principally to smectite, in deposits of moderately saline, nonalkaline lakes, as demonstrated in sediments of Searles Lake, California. Vitric tuffs in saline, alkaline playa-lake complexes are characteristically zoned from an outer fresh-water zone with unaltered glass or glass altered to smectite, an inner saline zone with zeolites, and an innermost highly saline zone with analcime and/or alkali feldspar, most commonly K-feldspar. Large-scale zoning of saline, alkaline type is exhibited by the Upper Jurassic Morrison Formation in the San Juan Basin, New Mexico and Arizona. Deep-sea sediments contain large volumes of clinoptilolite and phillipsite. The phillipsite predominates in Miocene and younger sediments and clinoptilolite in older sediments, possibly because clinoptilolite was favored in pre-Miocene sediments by more siliceous pore waters. Hydrolysis by ground water in open hydrologic systems can transform ash layers to bentonite or to zeolite-rich deposits. Temperature is the principal control on zeolite assemblages in burial-diagenetic and hydrothermal-geothermal systems. Igneous analcime has been documented in the Colima Volcanic Complex of Mexico.

K/Ar systematics of bentonite and shale in a contact metamorphic zone, Cerrillos, New Mexico

Abstract: To test the ability of illitic clay minerals to retain argon, K/Ar ages were measured on grain- size separates from the Cretaceous Mancos Shale and associated bentonites that have been transformed into K-bentonite near the contact with a large Tertiary igneous stock. The ages of size separates of illite/ smectite from the K-bentonite nearest the contact were internally concordant and matched the hornblende K/Ar age of the stock. In contrast, K/Ar data from day size fractions from shales adjacent to each K-bentonite were internally discordant with measured ages that were much greater than the age of the intrusion. Thus, significant radiogenic argon was retained by fine-grained detrital illite, even in shale samples very near the igneous contact. These results are convincing evidence that illitic clay minerals are excellent K/Ar clocks under conditions prevailing in sedimentary and diagenetic environments.

Influence of mineral weathering and catchment hydrology on drainage water chemistry in three upland sites in England and Wales

Abstract: Solute budgets and within system variations in water chemistry have been studied at three catchments in western Britain. The solute budgets showed a net export of calcium and silica from all three sites and of aluminium and magnesium from two. Hydrogen ion budgets, based on bulk precipitation inputs and streamwater outputs, underestimated inputs of acidity and fail to take account of within system sources. At two sites the aluminium and silica were derived from the soils and the calcium and magnesium from the bedrock compartment. There was little, if any, weathering of the mudstone and slate bedrocks at these two sites; calcium and magnesium were derived from carbonate veins and/or dolerite intrusions. At the third site, aluminium and silica were released from the upper soil, and calcium and magnesium from the lower soil or underlying, calcareous till. Catchment hydrology was, a major factor influencing the pattern and rate of weathering.

The polymer model of thermochemical clay mineral stability

Abstract: The Nriagu polymer model of 2:1 layer type clay minerals develops from the premise that clay minerals are condensation copolymers of solid hydroxides. In the Mattigod-Sposito formulation of the model, standard state chemical potentials (standard Gibbs energies of formation from the elements) of 2:1 clay minerals are predicted quantitatively with a linear correlation equation relating the standard Gibbs energy of the polymerization reaction (AG~ to the half-cell layer charge of the clay mineral and to the valence and ionic radius of the exchangeable cation. It is now shown that this correlation equation can be derived from two basic assumptions: (1) that the standard Gibbs energy change for the transfer of a cation in a pure hydroxide solid to a hydroxide component in the tetrahedral or octahedral sheet of a 2:1 clay mineral is independent of the nature of the cation and (2) that the difference between AG~ for the polymerization reaction to form a 2:1 clay mineral and AG~ for the same reaction to form the zero layer-charge analog of the clay mineral is proportional to the number of interlayer exchangeable cations per unit cell of the clay mineral and to the radius of its exchangeable cation. Both of these assumptions can be tested experimentally, independent of the polymer model.

Oxygen isotopes and the extent of diagenesis of clay minerals during sedimentation and burial in the sea

Abstract: Oxygen isotope ratios of <0.1-~m smectite in bottom sediments of the Mississippi River and the Gulf of Mexico near the mouth of the fiver have been determined to investigate diagenesis of land- derived clay minerals during sedimentation in the sea. No difference was detected in 6'80 (SMOW) between the river and the Gulf samples indicating that no smectite alteration or addition of neoformed smectite to the river samples took place during sedimentation. Thus, authigenic minerals in the fiver sediments cannot make up more than a few tenths of a percent of the bulk sediments. Similar results were obtained from 3 x 106-yr b.p. sediments buried to 80 to 600 m at Deep Sea Drilling Project site 323, Bellingshausen Abyssal Plain. No significant change with depth was noted in the 6180 of the <0.3-tzm size fraction, mostly smectite, of these land-derived sediments. On the basis of the 6~80 of the deepest sample, the maximum amount of authigenic minerals in the land-derived sediments during burial in the sea cannot be more than one or two percent of the bulk sediments. Hence, the alteration at seafloor temperatures of 25-45% of the <0.1-/zm size clays in 3 x 106 yr b.p. sediments reported in a previous study is not substantiated. The data demonstrate that land-derived smectite is stable in the sea, and that oxygen isotopes can be used to investigate the modes and the temperatures of formation of authigenic smectites in marine sediments that are younger than 25 x 106 yr and that formed below 25~

Some clay-related problems in engineering geology in North America

Abstract: Clay minerals are almost ubiquitous in soil and rock and are among the most reactive silicates. They affect the engineering behavior of soil and rock both as materials of construction and as foundation materials. In the petroleum industry, clay affects the permeability of reservoir formations, it is a common cap-rock, and it is also a constituent of the fluids used in drilling operations. Engineering behavior almost always involves clay-water interaction and this depends on the nature of water and solutions and on the composition and microstructure of the clay. In foundation engineering its role in soil-moisture interaction is illustrated by reference to problems resulting from the geological history of some North American soils and from engineering activities. In building materials, reference is made to its effect on concrete durability in aggregate-related problems. The importance of clay in petroleum engineering refers to authigenic clays in reservoir rocks, to clay behavior in the Alberta oil sands and to the use of clay minerals as a geothermal thermometer.--Modified journal abstract.