Showing papers on "Clay minerals published in 1988"

Cation Site occupancy in chlorites and illites as a function of temperature

Abstract: A B S T RA C T : The relationships between the composition and the crystallization temperature of chlorites and illites have been investigated in different geothermal fields and in particular the Los Azufres system in Mexico, considered to be a natural analogue to experimental laboratories, as the main changes in physical and chemical conditions and mineralogy are related to progressively increasing temperature with depth. Temperature was estimated from combined geothermometric approaches, and especially from fluid inclusion studies on quartz coexisting with clays. The Al(lv) content in the tetrahedral site of chlorites, and the K content and total interlayer occupancy of illites increase with temperature. These chemical changes are mainly related to the marked decrease in the molar fraction of the Si(lv)-rich end-members (kaolinite for chlorites, and pyrophyllite for illites) which become negligible at ~ 300~ Other chemical changes, such as the variation in Fe and Mg contents, are partly influenced by temperature, but are strongly dependent on the geological environment, and consequently on the solution composition. The empirical relationships between chemical variables and temperature were calibrated from 150-300~ but extrapolations at lower and higher temperatures seem possible for chlorites. Such geothermometers provide tools for estimating the crystallization temperature of the clays, and are important for the study of diagenetic, hydrothermal and low-T metamorphic processes. Clay minerals are the most abundant minerals in most of the geological environments submitted to temperatures from 50 ~ to 350~ where estimation of the crystallization temperature of the clay minerals may be difficult. Most of the classical geothermometers cannot be applied, fluid inclusions may be absent, and experimental data are scarce. Nevertheless, such temperature estimations are of critical importance for geological studies related to oil field exploration, as well as for diagenetic and low-T metamorphic processes. 1"here are three types of chemical or crystallographic change occurring in the clay fraction of rocks which may indicate temperature of crystallization. (1) The changes in the clay mineral assemblages described in studies of the burial metamorphism of sediments (Weaver, 1959; Dunoyer de Segonzac, 1970; Perry & Hower, 1970; Velde, 1977) and the thermal metamorphism of rocks in geothermal fields (Schoen & White, 1966; Steiner, 1968; Tomason & Kristmannsdottir , 1972; Cathelineau & Izquierdo, 1988). However, only the boundaries between two mineral assemblages may yield a temperature estimate, largely restricting their use.

Clay minerals for petroleum geologists and engineers

Abstract: These notes provide a general introduction of clays for the uninitiated, plus a review of traditional and more recent concepts for those who already know something about clays. The concept of fundamental illite particles and the phenomen of interparticle diffraction, relatively new concepts that are reshaping the manner of visualizing mixed-layer clays, are discussed in some detail. A discussion of shaly-sand log analysis, from a clay mineralogy perspective, is included. Isotope geology is discussed because of its potential for permitting a better understanding of temperatures and timing of diagenesis.

Structural Iron in Smectites

Abstract: In the words of Ross and Hendricks (1945), “Clay minerals . . . are the dominant materials of shales and surficial rocks and so are among the most important structural materials of the earth’s surface.” Clay minerals play a significant role in many aspects of life, ranging from their domination of the properties of the soils and sediments beneath us to their ubiquitous commercial use in many products and industries (Newman, 1984; Odom, 1984; Jepson, 1984, 1987). Iron in the crystal structures of these layer silicates significantly affects their physical and chemical properties, and thus is of great importance in the world around us.

Extraction of glyphosate herbicide from soil and clay minerals and determination of residues in soils

Abstract: Extraction of the herbicide glyphosate [N-(phosphonomethyl)glycine] from clay minerals and two soils was studied by a batch equilibrium technique. Experiments showed that, for most of the sorbent/solvent systems studied, the amount of herbicide extracted increased as pH increased, suggesting that sorption occurs through ion exchange and hydrogen bonding. Alkaline solutions of kaolinite, iron oxide, and two Calvin silt loam soil samples showed resorption of glyphosate after an initial desorption step. Determination of glyphosate residues in soils was performed by derivatization of soil extracts with 9-fluorenylmethyl chloroformate and analysis by HPLC with fluorometric detection. Glyphosate was successfully recovered from sandy soils at 0.5 ppm by triplicate extraction with 0.1 M KH2P04 and 30-fold concentration. For soils with high clay content, acceptable recovery at 1.0 ppm was achieved with triplicate extraction using 0.2 M KOH.

SIMS depth profiles of weathered plagioclase and processes affecting dissolved Al and Si in some acidic soil solutions

Abstract: Many natural catchments are now under threat of acidification from natural and anthropogenic sources. Acids introduced to the catchments are neutralized by reaction with soil constituents (including clay minerals and feldspars) and a better understanding of the mechanisms of neutralization is required to evaluate effects of acid deposition in sensitive catchments. The response of feldspars to these acids has been generally studied by monitoring the composition of the weathering solutions. The dissolution of albite and perthite is initially incongruent, with Na- and K-depleted residues produced at the expense of the feldspars1–4. Such residues can be detected by secondary ion mass spectrometry using the specimen isolation technique provided the residues are greater than ˜40 A thick. Here we report secondary ion mass spectrometric studies of naturally weathered feldspar surfaces. The acidic soil waters of many catchments have high contents of total dissolved aluminium5–10, including some from the Plastic Lake Catchment in Ontario, and we consider the effects of feldspar dissolution on Al contents of acidic soil waters.

Magnetic Properties of Iron in Soil Iron Oxides and Clay Minerals

Abstract: The pie chart in Fig. 14-1 indicates the abundance of Fe relative to other major elements in the earth’s crust. It is the only one of the nine to bear a magnetic moment in its compounds. The bar chart compares the abundance of Fe with that of other magnetic ions, on a logarithmic scale. Since Fe is approximately forty times more abundant than all the others put together, it follows that magnetic properties of soils and clay minerals derive essentially from the Fe they contain. Magnetic measurements are highly specific to Fe, but, as we shall see, they are much more sensitive to some mineral forms (e.g., magnetite, maghemite, pyrrhotite) than to others.

Stabilisation and treatment of clay soils with lime. part 1 - basic principles

Abstract: Clay soil can be stabilised by the addition of a small percentage, by weight, of lime. This produces an improved construction material. Generally the amount of lime needed to modify a clay soil varies from 1 to 3 per cent, whilst that required for cementation varies from 2 to 8 per cent. Montmorillonitic clay soils respond more rapidly to lime treatment than do those in which kaolinite is the dominant clay mineral. When lime is added to clay soils, calcium ions are combined initially with or adsorbed by clay minerals which leads to an improvement in soil workability, that is, to an increase in the plastic limit of the clay and generally to a decrease in its liquid limit. The optimum lime additive for maximum increase of the plastic limit of the soil is referred to as the lime fixation point. Lime added in excess of the fixation point is utilised in the cementation process and gives rise to an increase in soil strength. The initial increase in strength has been attributed to the formation of poorly ordered reaction products which surround the clay materials. However, the development of long-term strength appears to be due to the gradual crystallisation of structurally-ordered new minerals from the initial disordered reaction products. The principle uses of the additions of lime to clay soils is for, firstly, stabilisation of subbases and subgrades in pavement construction and, secondly, to dry out wet soils. Lime treatment also has been used to stabilise embankments and canal linings, and to improve foundation soils. In the latter instance soil is stabilised beneath strip or raft foundations, or lime piles or columns are formed. (TRRL)

Microstructures, formation mechanisms, and depth-zoning of phyllosilicates in geothermally altered shales, Salton Sea, California

Abstract: Scanning, transmission, and analytical electron microscopy studies of shales from the Salton Sea geothermal field revealed that phyllosilicates progress through zones of illite-muscovite (115°−220°C), chlorite (220°−310°C), and biotite (310°C) These phyllosilicates occur principally as discrete, euhedral to subhedral crystals which partly fill pore space The structural and chemical heterogeneity, which is typical of phyllosilicates in shales subject to diagenesis, is generally absent Textures and microstructures indicate that the mineral progression involves dissolution of detrital phases, mass transport through interconnecting pore space, and direct crystallization of phyllosilicates from solution Phyllosilicate stability relations indicate that either increase in temperature or changing ion concentrations in solutions with depth are capable of explaining the observed mineral zoning Textural and compositional data suggest that the observed mineral assemblages and the interstitial fluids approach equilibrium relative to the original detrital suites The alteration process may have occurred in a single, short-lived, episodic hydrothermal event in which the original detrital phases (smectite, etc) reacted directly to precipitate illite, chlorite, or biotite at different temperatures (depths) without producing intermediate phases

Compositional and Solubility Relationships Between Aluminum‐hydroxyinterlayered Soil‐Smectites and Vermiculites

Abstract: Coarse clay fractions (2-0.2 ) of selected soil samples containing variable quantities (10-52%) of Al-hydroxyinterlayered smectite (HISM) or vermiculite (HIV) were investigated by XRD, thermal, elemental and solution composition analyses. The HISM vs. HIV nature of the sample was determined from the smectitic or vermiculitic origin of the sample and by alkylammonium ion exchange, expansion with glycerol and resistance to collapse after K-saturation and heating at 300° and 550 °C. X-ray diffraction and thermal analysis of tetradecylammonium exchanged clays and structural formulae calculations indicated all hydroxyinterlayered minerals, except for one HISM, to have high layer charge deficiencies (X > 0.5 equivalents per 0.5 unit cell). A greater portion of the total charge deficiency was satisfied by [Al(OH)x] in HIV minerals which resulted in generally higher free energies of formation . Hydroxyinterlayered smectites on the other hand, exhibited higher cation exchange capacities and higher OH/Al ratios in the hydroxyinterlayer material. Compositions of soil solutions in contact with these minerals supported a metastable HISM region in relatively Si-enriched solutions and a metastable or stable HIV region in somewhat Si-deficient solutions comparable to those supporting the stability of kaolinite. Structural formulaeand soil solutioncompositions of the studied samples appeared to be consistent with the dynamic nature of these minerals in soil environments in terms of mineralogical distribution, physicochemical behavior, and stability. View complete article To view this complete article, insert Disc 5 then click button8

The effect of Aeolian accessions on soil development on granitic-rocks in south eastern Australia. II. Oxygen-isotope, mineralogical and geochemical evidence for Aeolian deposition

Abstract: Oxygen-isotope abundance in quartz grains, total chemical analyses and clay mineral data are used to identify aeolian deposits in four soil profiles developed on granitic rocks. Results indicate that quartz fractions derived from I-type granitic rocks have a18O values less than 10.7%, whereas fine sand-sized (50-31 µm) quartz separates from the same soils have a18O values of > 11.6?. Similar, but less marked, differences were observed in a soil on an S-type granitic rock, suggesting that addition of aeolian material to all the soils investigated has been an important process of soil formation. X-ray diffraction data indicate the presence of decreasing proportions of clay mica h the soils with increasing distance from probable sources of aeolianites in the Riverine Plain, raising the possibility that clay mica, along with other clay minerals and clay-size quartz, may have been also deposited by wind in the soils. Titanium/zirconium elemental ratios are less useful indicators of aeolian accession because of complications arising from the weathering of biotite in the underlying granitic rocks. Probable losses of yttrium from the soils also appear to result from weathering of materials derived from the granitic rocks, although some data indicate that zirconium/yttrium ratios for the 50-2 µm fractions may also be indicative of aeolian accession.

The effect of weathering on the strength of London Clay

Abstract: A detailed study is presented of the effect of weathering on the undrained and effective stress strengths of London Clay from a site at South Ockendon, Essex. A limited investigation of the chemistry and clay mineralogy was also carried out. It is concluded that the effect of weathering is to reduce the apparent degree of overconsolidation. This effect is seen in the undrained strength-water content relationship of the most weathered clay, which shows a 4% higher water content at a given strength than the unweathered clay. There is a corresponding reduction of the overconsolidation ratio from about 40 to about 20. In effective stress terms the corresponding strength change is given by a reduction of c ′ from 28 kPa to a minimum value of about 9 kPa, assuming that o′ (= 20°) remains unchanged by the weathering.

Origin, physical, and mineralogical nature of red clays: The Pacific Ocean Basin as a model

Abstract: Extensive examination of North Pacific Basin red clays by scanning and transmission electron microscopy reveals that the mean constituent of the red clays are illite-rich argillaceous or shale clasts, quartz and authigenic smectite. The main source of the shale clasts and quartz are aeolian in nature and are derived mainly from African and Asian shales. Illite-rich argillaceous or shale clasts are identifiable by their morphology (high degree of roundness), selected area diffraction, and their unique fracture characteristics created by an ultra thin-sectioning process. This allows for the identification and differentiation of illite-rich shale clasts from other clays, including detrital illite, kaolinite, and smectite. Geotechnical examination of the red clays indicate that they are overconsolidated: the preconsolidation stress is in all cases larger than the vertical effective stress. The overconsolidation is attributed to the strong bonding of argillaceous or shale clasts, quartz and other particulate matter by x-ray amorphous and well developed crystalline sheets of authigenic smectite characterized by high surface activity.

Formation mechanisms of illite, chlorite and mixed-layer illite-chlorite in Triassic volcanogenic sediments from the Southland Syncline, New Zealand

Abstract: Clay minerals from the three principal kinds of zeolitic sediments from the type area for zeolite facies alteration, the Triassic Murihiku Supergroup, Southland, New Zealand, have been studied by TEM. Bentonitic tuff consists largely of smectite and heulandite with minor illite; they occur as replacements of glass shards and are inferred to be direct alteration products of tuff alteration. Both analcime- and laumontite-rich tuffs contain chlorite, illite and mixed-layer illite-chlorite, including 1∶1 mixed-layer sequences. Subhedral to euhedral phyllosilicate crystal shapes and other textural features imply that phyllosilicates crystallized from solution derived in part by dissolution of precursor smectite. Intralayer transitions involving illite and chlorite are inferred to be products of crystallization rather than direct alteration and replacement. Petrographically similar bentonitic and analcimized tuffs overlap each other in the stratigraphic section, supporting earlier observations that there is no systematic change in smectite relative to the illite plus chlorite derived from smectite in sections up to 8.5 km thick. The data imply that smectite may be metastable relative to illite plus chlorite. Permeability and fluid chemistry are inferred to be as significant as temperature in promoting reactions in clay minerals as well as zeolites during burial metamorphism.

Nature, distribution & origin of clay minerals in grain size fractions of sediments from manganese nodule field, Central Indian Ocean Basin

Abstract: DT, IR and X-ray diffraction < 1,1 -2 and 2-4 /μm) of sediments from the Central Indian Ocean Basin. Results indicate that there are 2 smectite minerals (montmorillonite and Fe-rich montmorillonite). Montmorillonite is present in all size fractions of sediments, whereas Fe-rich montmorillonite is present onlyin < 1 and 1-2 μm fractions of siliceous and < lμm fractions of pelagic clays. Distribution of clay minerals suggests that illite, chlorite and kaolmite are the detrital products from Ganges and Brahmaputra and montmorillonite is derived from the weathering of the ridge rocks.Fe-rich montmorillonite in siliceous and pelagic clays is a result of early diagenetic processes. Size fraction studies suggest that montmorillonite tends to crystallise in <2μm size range.

Sequential extraction of iron, manganese, aluminum, and silicon in soils from two contrasting watersheds

Abstract: Soil samples from two contrasting forested watersheds on the U.S. Department of Energy Oak Ridge Reservation in Oak Ridge, TN, were chosen for selective extraction of organics, Fe, Mn, and aluminosilicates. The extracts were analysed for Fe, Mn, Al, and Si, and the results were evaluated in terms of pedogenic processes. The clay mineralogy was determined on a subset of the samples. Differences between the watersheds were observed in clay mineralogy and in the vertical distribution of extractable Mn. (...)

Weathering of Chlorite and Vermiculite in Ultramafic Rocks of Cabo Ortegal, Northwestern Spain

Abstract: Chloritic veins in serpentinite and their weathering products were analyzed by X-ray pow- der diffraction (XRD) and X-ray fluorescence spectrometry (XRF). Chlorite formed during the Hercynian- age orogenesis had apparently been partly transformed to high-charge vermiculite during subsequent metamorphism of the rocks. The idealized structural formulae for these minerals are (mlL9Fea+0.zFe2+ o.4Mg9.2Cr0.z)(S is.sA12.2)O20(OH )l 6 and Xl.3(Fe3+o.7Fe2+ o.~Mg5.zNio.l)(S is.sA12.E)OEo(OH )4, respectively. This transformation appears to have taken place by the removal of the hydroxy-interlayer from the chlorite without major effect on the rest of the structure. It is not clear whether other hydroxy- interlayered vermiculites containing less tetrahedral aluminum were intermediate weathering products or inherited minerals. The ultimate weathering product of chlorite and vermiculites was a Fe 3+-rich smectite, which probably formed by precipitation from solution.

Effects of clay mineralogy and soil sodicity on soil infiltration rate

Abstract: Crust formation and infiltration rates and their dependence on the exchangeable sodium percentage (ESP) of South African (SA) soils, with kaolinite and illite as the dominant clay minerals, were studied by subjecting them to simulated rain. The final infiltration rate (FIR) values of these soils at ESP ca. 2,5 were compared to values reported for Israeli soils having similar clay content but with smectite as the dominant clay mineral. The SA soils have higher FIR values, which indicates that they were less affected by raindrop impact than the smectitic (Israeli) soils. It is therefore suggested that kaolinitic and illitic soils are less dispersive than smectitic soils. The effect of ESP on infiltration was found also to depend on the clay mineralogy of the soil. The FIR values of the kaolinitic soil with no smectite were only slightly affected by ESP. When smectite was present in kaolinitic soil, the susceptibility of the soil to sodicity, as reflected by crust formation, increased. The illitic soil was f...

Layered Silicates as Catalysts

Abstract: The structure of layered silicates, mainly smectites, and the synthesis of similar minerals, including fixed clays with pores exceeding in size the inlet apertures in zeolites are examined. Such clays are capable of catalysing the reactions of even large molecules, having a kinetic diameter in excess of 1.0 nm, which cannot penetrate into zeolite cavities for steric reasons. Certain reactions occuring in the presence of layered and fixed clay minerals are considered. The bibliography includes 184 references.

Characteristics of clays in an oxisol-- spodosol toposequence in amazonia (brazil)

Abstract: The clay fraction of soils from a toposequence developed on a sandy clay Tertiary sediment in the Brazilian Amazonia was studied. Clayey Acrorthox located at the upper part of the sequence have transformed progressively into sandy Tropohumods down the slope. Along the slope important chemical and mineralogical changes linked to modifications in the weathering conditions were observed. In the Acrorthox the hydrolysis process largely prevails and the clay fraction is composed mainly of Fe-rich kaolinite. Fe and AI amorphous compounds become increasingly abundant along the slope. In the Spodosols, hydrolysis and acidocomplexo- lysis processes have both been effective, and the clay fractions contain not only more gibbsite, but also amorphous materials which are particularly abundant in the Bh horizons. In the area near Manaus (Brazil), Acrorthox (sols ferrallitiques), Paleudult (sols ferrallitiques A diff6renciation texturale) and Tropohumod (podzols) are associated in soil toposequences. According to Klinge (1965), the podzols have developed from sandy materials covering the valley bottoms, and the Acrorthox from a more clayey sediment which has settled on the plateau surfaces. Chauvel et al. (1987) and Lucas et al. (1987) demonstrated that the whole toposequence was derived from the same parent material, known as the Barreiras sediment. From the upper to the lower part of the sequence, Acrorthox was progressively transformed into podzols through destruction of the clays leaving quartzose residual material. According to Chauvel et al. (1987) the clays (kaolinite and gibbsite) have been weathered by acido- complexolysis (podzolization) which involves complexing organic acids both in the weathering of the clay fraction and in the removal of A1 from the soil profile. However, Lucas et al. (1987) considered that a previous clay impoverishment of the ferrallitic material was necessary before podzolization. The purpose of this paper is the geochemical and mineralogical characterization of the clay fractions (< 2/zm) in order to obtain more information about the weathering conditions, and particularly the respective roles of the podzolization and hydrolysis processes in the development of the soil toposequence.