Showing papers in "Clays and Clay Minerals in 1986"
TL;DR: Several clay-organic complexes were synthesized by placing quaternary ammonium cations on smectite by cation exchange and they were then examined for their ability to adsorb phenol and several of its chlorinated congeners as discussed by the authors.
Abstract: Several clay-organic complexes were synthesized by placing quaternary ammonium cations on smectite by cation exchange. They were then examined for their ability to adsorb phenol and several of its chlorinated congeners. The organic cations used were: hexadecylpyridinium (HDPY+), hexadecyltri- methyl ammonium (HDTMA+), trimethylphenyl ammonium (TMPA+), and tetramethylammonium (TMA+). The complexes containing long-chain alkyl (hexadecyl) groups were the most hydrophobic and adsorbed the phenols from water in proportion to their hydrophobicities, which increase with chlorine addition (phenol < chlorophenol < dichloropohenol < trichlorophenol). With n-hexane as the solvent, different adsorption was found which depended on the type and degree of solvent interactions with the compound and the clay-organic complex. Thus, the amount of adsorption of these phenols on clay-organic complexes was dependent on the relative energies of adsorbent-adsorbate and adsorbate-solvent inter- actions.
435 citations
TL;DR: In this article, a cross-linked montmorillonite was introduced by cation exchange with polymeric Ti cations, formed by partial hydrolysis of TiCl4 in HCl.
Abstract: Titanium was introduced into the montmorillonite structure by cation exchange with polymeric Ti cations, formed by partial hydrolysis of TiCl4 in HCl. On further hydrolysis and heating, TiO2 pillars in the form of anastase were formed between the montmorillonite layers. The resulting TiO2-cross-linked montmorillonites possessed surface areas in the range 200–350 m2/g and pore volumes of about 0.2 cm3/g and were thermally and hydrothermally stable to 700°C. The basal spacing of products heated at temperatures > 200°C was about 28A, as determined by X-ray powder diffraction and by N2-desorption pore-size analysis. The surface area increased and the pore volume decreased with increasing HCl-concentration in the Ti-solution. The uptake of TiO2 by the montmorillonite, the surface area, and the pore volume increased with increasing amount of Ti added in the preparation, to about 10 mmoles of Ti/g of montmorillonite. A further increase in the amount of Ti added resulted in a decrease in surface area, but the pore volume and the uptake of TiO2 remained almost constant. The high porosity and the interlayer spacing of the product are consistent with a structure similar to that previously proposed for smectites, cross-linked with hydroxy-Al oligocations.
290 citations
TL;DR: In this article, a suite of Georgia kaolinites, ranging from well-ordered to very poorly ordered samples, were studied to explore correlations between degree of structural disorder, geological environment, Fe3+ content, electron paramagnetic resonance (EPR) spectrum, and infrared (IR) hydroxyl-stretching band frequencies and bandwidths.
Abstract: A suite of Georgia kaolinites, ranging from well-ordered to very poorly ordered samples, were studied to explore correlations between degree of structural disorder, geological environment, Fe3+ content, Fe3+ electron paramagnetic resonance (EPR) spectrum, and infrared (IR) hydroxyl-stretching band frequencies and bandwidths. Samples from different localities showed a wide range of disorder which appears to be related to differences in their geological environments. High iron content correlated strongly with low degree of order. The areas of both the I and E components of the EPR spectrum and the fractional I area correlated inversely with degree of order. Fourier-transform IR studies of kaolinites and dickites showed that (1) interlayer hydrogen bonding is weaker in dickite than in kaolinite; (2) frequency of the ν1 stretching band of the inner-surface hydroxyls increases sequentially from well-ordered kaolinite through the disordered structures to well-ordered dickite, which is consistent with a model for disorder based on vacancy displacement; and (3) the character and temperature dependence of the inner hydroxyl-stretching band is not compatible with the crystal structures of kaolinite and dickite as refined by Suitch and Young.
265 citations
TL;DR: In this article, the authors studied the smectite to illite reaction in argillaceous sediments from depths of 1750, 2450, and 5500 m in a Gulf Coast well.
Abstract: The smectite to illite reaction was studied by transmission and analytical electron microscopy (TEM/AEM) in argillaceous sediments from depths of 1750, 2450, and 5500 m in a Gulf Coast well. Smectite was texturally characterized as having wavy 10- to 13-A layers with a high density of edge-dislocations, and illite, as having relatively defect-free straight 10-A layers. The structures of smectite and illite were not continuous parallel to (001) at smectite-illite interfaces. AEM data showed that the smectite and illite were chemically distinct although smectite had a more variable composition. Mite formation appeared to have initiated with the growth of small packets of illite layers within subparallel layers of smectite matrix. With increasing depth, ubiquitous thin packets of illite layers increased in size until they coalesced. A model for the transition requires that the structure of smectite was largely disrupted at the illite-smectite interface and reconstituted as illite, with concomitant changes in the chemistry of octahedral and tetrahedral sites. At least partial Na-K exchange of smectite preceded illite formation. Transport of reactants (K, Al) and products (Na, Si, Fe, Mg, H20) through the surrounding smectite matrix may have taken place along dislocations. The smectite-to-illite conversion process for the studied samples does not necessarily appear to have required mixed-layer illite/smectite as an intermediate phase, and TEM and AEM data from unexpanded samples were found to be incompatible with the existence of mixed-layer illite/smectite in specimens whose XRD patterns indicated its presence.
242 citations
TL;DR: In this paper, synthetic sodium bimessite, having a cation exchange capacity of 240 meq/100 g (cmol/kg) was transformed into Li, K, Mg, Ca, Sr, Ni, and Mn2+ cationic forms by ion exchange in an aqueous medium.
Abstract: Synthetic sodium bimessite, having a cation-exchange capacity (CEC) of 240 meq/100 g (cmol/kg) was transformed into Li, K, Mg, Ca, Sr, Ni, and Mn2+ cationic forms by ion exchange in an aqueous medium. Competitive adsorption studies of Ni and Ba vs. Mg showed a strong preference for Ni and Ba by bimessite. The product of Mg2+-exchange was buserite, which showed a basal spacing of 9.6 A (22°C, relative humidity (RH) = 54%), which on drying at 105°C under vacuum collapsed to 7 A. Of the cation- saturated bimessites with 7-A basal spacing, only Li-, Na-, Mg-, and Ca-bimessites showed cation exchange. Heating bimessite saturated with cations other than K produced a disordered phase between 200° and 400°C, which transformed to well-crystallized phases at 600°C. K-exchanged bimessite did not transform to a disordered phase; rather a topotactic transformation to cryptomelane was observed. Generally the larger cations, K, Ba, and Sr, gave rise to hollandite-type structures. Mn- and Ni-bimessite transformed to bixbyite-type products, and Mg-bimessite (buserite) transformed to a hausmannite-type product. Li-bimessite transformed to cryptomelane and at higher temperature converted to hausmannite. The hollandite-type products retained the morphology of the parent bimessite. The mineralogy of final products were controlled by the saturating cation. Products obtained by heating natural bimessite were similar to those obtained by heating bimessite saturated with transition elements.
223 citations
TL;DR: The Dunbarton Triassic basin, South Carolina, is a good example of osmotically induced potentials as discussed by the authors, where a unique osmotic cell is created by the juxtaposition of fresh water in the overlying Cretaceous sediments against the saline pore water housed within the membrane-functioning sediments.
Abstract: Clays can act as osmotic membranes and thus give rise to osmotically induced hydrostatic pressures. The magnitude of generated osmotic pressures in geologic systems is governed by the theoretical osmotic pressure calculated solely from solution properties and by value of the membrane's three phe- nomenological coefficients: the hydraulic permeability coefficient, Lv; the reflection coefficient, tr; and the solute permeability coefficient, 60. Generally, low values of Lp correspond to highly compacted membranes in which ~ is near unity and r approaches zero. Such membrane systems should give rise to initially high osmotic fluxes and gradual dissipation of their osmotic potentials. The high fluid pressures in the Dunbarton Triassic basin, South Carolina, are a good example of osmotically induced potentials. A unique osmotic cell is created by the juxtaposition of fresh water in the overlying Cretaceous sediments against the saline pore water housed within the membrane-functioning sediments of the Triassic basin. Because wells penetrating the saline core of the basin show anomalously high heads relative to wells penetrating the basin margins, the longevity of this osmotic cell is probably dictated by the rate at which salt diffuses out into the overlying fresh water aquifer.
209 citations
TL;DR: In this paper, a double-layer hydrotalcite-like compound was synthesized by using pressure and temperature, pressure, the Al/(Al + Mg) ratio, and the CO2 content of the starting material.
Abstract: Hydrotalcite-like compounds, [Mg1-xAlx(OH)2]x+ [xX−·n H2O], where X− = ½CO32− or OH−, were prepared by hydrothermal syntheses at $$P_{H{_2}O}=100\;MPa$$
and T = 100°–350°C. Starting materials were MgO, γ-Al2O3, H2O, and MgC2O4·2H2O. The synthesis depended on temperature, pressure, the Al/(Al + Mg) ratio x, and the CO2 content of the starting material. Previously an Al content of x = 0.33 was thought to be the upper limit in these double-layer compounds, but by using pressure the Al-content was increased to x = 0.44. Up to x = 0.33, a0 decreased linearly to about 3.04 A, but for x ≥0.33, a0 remained nearly constant at this value. For the synthesized products the layer thickness c’ varied between 7.40 and 7.57 A in contrast to the natural phases wherein c’ varies from 7.60 to 7.80 A. At higher temperatures CO2-free syntheses, i.e., those without Mg-oxalate, resulted in a disordered hydrotalcite-like phase. The transition temperature between the ordered and the disordered hydrotalcite-like phase depended on the Al-content, x.
161 citations
TL;DR: In this article, chemical data from three different series of diagenetic illite/smectites (I/S), analyzed statistically by two regresion techniques, indicate that the content of fixed-K per illite layer is not constant, but ranges from ~0.55 per O10(OH)2 for illite layers in randomly interstratified I/S (R=0, >50% smectite layers) to ~ 1.0 per O 10(OH 2 ) for illiters formed in ordered I/s (R>
Abstract: Chemical data from three different series of diagenetic illite/smectites (I/S), analyzed statistically by two regresion techniques, indicate that the content of fixed-K per illite layer is not constant, but ranges from ~0.55 per O10(OH)2 for illite layers in randomly interstratified I/S (R=0; >50% smectite layers) to ~ 1.0 per O10(OH)2 for illite layers formed in ordered I/S (R>0; <50% smectite layers). By extrapolation of the experimental data, the following chemical characteristics were obtained for end-member illite derived from the alteration of smectite in bentonite: average fixed-K per illite layer = 0.75 per O10(OH)2; total charge = about -0.8; cation-exchange capacity = 15 meq/100 g; surface area (EGME) = 150 m2/g.
156 citations
TL;DR: In this paper, diagenetic reactions of di-and trioctahedral clay minerals were compared in Brazilian offshore, basinal sediment sequences of Cretaceous age and the change from disordered to ordered interstratifications of chlorite/saponite occurred in the tem- perature range 60%-70~ at a vitrinite reflectance value of about 0.65.
Abstract: Burial diagenetic reactions of di- and trioctahedral clay minerals were compared in Brazilian offshore, basinal sediment sequences of Cretaceous age. Originally dioctahedral smectite-rich shales of three basins -- Potiguar, Ceara, and llha de Santana -- exhibited the classical smectite-to-illite burial pattern. Trioctahedral clay-rich shales and trioctahedral clay-mineral cements in sandstones, however, showed a burial sequence of saponite to mixed-layer chlorite/saponite with progressive increase in the percentage of chlorite layers with increasing burial depth. The change from disordered to ordered interstratifications of chlorite/saponite occurred in the tem- perature range 60%-70~ at a vitrinite reflectance value of about 0.65. These values are lower than those found for the ordering of illite/smectite clays. Increasing substitution of Al for Si in tetrahedral sites, followed by fixation of interlayer hydroxide sheets was found to be the major chemical change promoting transformation of saponite to chlorite via corrensite.
153 citations
TL;DR: In this article, a variety of solid-state transformation mechanisms were tested with a stochastic model, which accounts for interactions among clay layers, and the model produces most successful results when the reaction of smectite layers with one illite nearest neighbor is favored over smectites with no illite neighbors by a factor of about two.
Abstract: A layer-by-layer mechanism explains important features of mixed-layer clay minerals formed during the illitization of smectite, including the occurrence of randomly interstratified illite/smectite, the transition to ordered interstratifications, and the development of long-range ordering. A variety of solid-state transformation mechanisms were tested with a stochastic model, which accounts for interactions among clay layers. The model produces most successful results when the reaction of smectite layers with one illite nearest neighbor is favored over smectites with no illite neighbors by a factor of about two, and over those with two illite neighbors by a factor of ten or more. Synthetic X-ray powder diffraction patterns calculated from model results compare well with those of illite/smectite minerals. These results suggest a new kinetic rate law. Solutions to this rate law for reaction within sediments undergoing burial give mineralogical profiles with depth similar to those observed in subsiding sedimentary basins.
133 citations
TL;DR: The morphology of illite/smectite (I/S) from deeply buried bentonites and hydrothermally altered Tertiary volcanic rocks from Japan changes in parallel with the proportion of expandable layers in the I/S as mentioned in this paper.
Abstract: The morphology of illite/smectite (I/S) from deeply buried bentonites and hydrothermally altered Tertiary volcanic rocks from Japan changes in parallel with the proportion of expandable layers in the I/S. As viewed by scanning electron microscopy, the morphologies range from the typical “cornflake,” “maple leaf,” or “honeycomb” habit of smectite to the typical platy or scalloped (with curled points) habit of illite. Although the changes are more subtle near either end member, at a composition of 60-70% illite layers, the morphology changes from sponge-like or cellular to platy or ribbon-like. The change of morphology at this composition correlates with a change in layer stacking from turbostratic to rotational ordering of the 1Md type. Turbostratic stacking can be thought of as randomly distributed translations of successive layers by any magnitude and in any direction. The rotationally ordered structure, which allows nearly precise juxtaposition of quasihexagonal oxygen surfaces from adjacent layers, probably permits more crystalline regularity in the a-b plane, which promotes a more plate-like or sheet-like habit.
TL;DR: In this paper, structural formulae of the illitic clays were calculated using X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) data.
Abstract: Chemical analysis by X-ray fluorescence (XRF) and calculated structural formulae of clay-size fractions of smectites from Cretaceous bentonites and illitic clays from Cretaceous, Devonian, and Or- dovician bentonites and Jurassic and Permian sandstones indicate the nature and extent of various types of ionic substitution. The determination of tetrahedral (A1, Si) and octahedral (A1, Mg, Fe) composition shows the variable chemistry of these materials. Structural formulae of the illitic clays show that they have tetrahedral charges between 0.4 and 0.8 per half unit cell, and can be divided into phengitic types having octahedral charges of 0.2-0.4 and muscovitic types having octahedral charges <0.2. Evaluation of the formulae in the light of X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) data shows that the occupancy of non-exchangeable interlayer sites (predominantly K) varies from 47% to 90% of that of ideal muscovite. In some minerals as muqh as 20% of these sites is occupied by ammonium ions (determined independently). The amount of surface silicate charge balanced by non- exchangeable cations versus that balanced by exchangeable cations has been examined in conjunction with TEM data and suggests that in most samples the charges are about equal. The octahedral composition of smectites in Cretaceous bentonites precludes their having served'as transformation precursors for most of the Cretaceous illitic bentonites. The results suggest that these ilfitic clays originated by neoformation.
TL;DR: In this paper, an ochreous precipitate isolated from a stream receiving acid-sulfate mine drainage was found to consist primarily of goethite and lesser amounts of ferrihydrite-like materials.
Abstract: An ochreous precipitate isolated from a stream receiving acid-sulfate mine drainage was found to consist primarily of goethite and lesser amounts of ferrihydrite-like materials. The Fe-oxide fraction, including goethite, was almost totally soluble in acid ammonium oxalate. Similar materials were produced in the laboratory by hydrolysis of ferric nitrate solutions containing 250 to 2000 μg/ml sulfate as Na2SO4. Initial precipitates of natrojarosite transformed to Fe-oxides upon aging for 30 days at pH 6.0. The proportion of goethite in the final products decreased with increasing sulfate (SO4/Fe = 0.2 to 1.8) in the initial hydrolysis solutions; only ferrihydrite-like materials were produced at SO4/Fe ratios > 1.5. Variations in SO4/Fe solution ratios also produced systematic changes in the color (10R to 7.5YR) and surface areas (49 to 310 m2/g) of the dried precipitates, even though total S contents were relatively constant at 2.5 to 4.0%.
TL;DR: In this paper, a method using Li saturation and heating to 250~ to differentiate montmorillonite from beidellite and nontronite has been developed, which provides more mineralogical information than the often-used arbitrary dividing point between Montmorillonites and beidesllite at 50% tetrahedral charge.
Abstract: A method using Li saturation and heating to 250~ to differentiate montmorillonite from beidellite and nontronite has been developed. The test utilizes three washings with 3 M LiCl and two washings with 0.01 M LiC1 in 90% methanol to prevent dispersion. An 'infinitely thick' sample (6-8 mg/ cm z) on a glass slide is used to avoid the effects of the reaction of a thin clay film with sodium of the slide when it is heated at 2500C. Solvation with glycerol rather than ethylene glycol is used, because all of the Li smectites studied expanded to some extent in ethylene glycol after the heating. The smectites included several montmorillonites, a nontronite, and saponites. The presence of interstratified mont- morillonite and beidellite layers was clearly shown by the test for several smectite samples, including the so-called beidellites from Beidell, Colorado, and Chen-yuan, Taiwan, and several soil clays. The test thereby provides more mineralogical information than the often-used arbitrary dividing point between montmorillonite and beidellite at 50% tetrahedral charge. Heating the Li-saturated clays at 250*C caused substitution of 35 to 125 meq/100 g of nonexchangeable Li. These amounts exceeded the changes in cation-exchange capacity plus Li by 4 to 21 meq/100 g, except for the end-member beidellite from the Black Jack mine, Idaho. Fusion with LiNO3 at 300~ could not be used to differentiate between smectites instead of washin~ with LiC1 solution and heating to 250~ because fused montmorillonite subsequently expanded to 18 A with glycerol. Large increases in nonexchangeable Li were caused by the fusion of smectites, a vermiculite, and two partially expanded micas.
TL;DR: In this article, a closed-form equation was derived that describes the powder-ring distribution factor as a function of 20, soller slit collimation, and or*, which was defined as the standard deviation of an axiaUy symmetrical Gaussian orientation function.
Abstract: Abstraet--A closed-form equation was derived that describes the powder-ring distribution factor as a function of 20, soller slit collimation, and or*, which is defined as the standard deviation of an axiaUy symmetrical Gaussian orientation function. Methods were developed for measuring a* in the reflection mode by means of a 0/20 diffractometer. Six experimental arrangements for a sedimentary chlorite showed widely different intensity ratios of the 001/005 reflections and gave a standard deviation of 5.8% when corrected by the theory. The absolute integrated intensities of the 003 reflection from eleven illite samples provided an eight-fold maximum range which, when corrected, yielded a standard deviation of The intensity distributions within each of two X-ray powder diffraction patterns obtained from instruments with different soller-slit configurations could not be directly compared at low diffraction angles unless corrections, based on a*, were introduced to allow for the differences in axial divergence.
TL;DR: In this article, a microprobe analysis of 16 discrete I/S clays from the southern San Joaquin basin was performed and the results indicated an average montmo- rillonite composition of: (Cao.2Ko.~sNao.03)(Si7.7Alo.3)O2o(OHL �9 n H20.35Mgo.
Abstract: The southern San Joaquin Valley contains more than 7 km of sedimentary fili, largely Miocene and younger in age. Ancient depositional environments ranged from alluvial fans at the basin margins to turbidite fans toward the basin center. Mixed-layer illite/smectite (I/S) dominates the 80% expandable layers occur at present burial temperatures of 120~176 in Miocene sandstones and shales. This highly expandable I/S is restricted to areas covered by thick deposits (1000-2500 m) of Pleistocene sediments. Rocks of similar age and at equivalent tem- peratures, but covered by <900 m of Pleistocene sediments, contain I/S having low expandabilities (<30%). Microprobe analyses of 16 discrete smectite and smectite-rich I/S clays indicate an average montmo- rillonite composition of: (Cao.2Ko.~sNao.0(A13.oFe3+o.35Mgo.TsTio.03)(Si7.7Alo.3)O2o(OHL �9 n H20. Smectite in I/S-rich clays of Gulf Coast shales has a similar composition except for lower octahedral A1/ Fe ratios (A1/Fe vl = 3.1), compared with the San Joaquin samples (A1/Fe w = 8.6). Residence time at different temperatures appears to be an important influence on the percentage of smectite layers in I/S from the San Joaquin basin. Areas containing I/S with high expandabilities (e.g., 95% smectite layers) have a time-temperature index (TTI) of 4.0-4.5 at 120~ whereas areas containing I/S with low expandabilities (e.g., 30% smectite layers) have a TTI of 5.0. Present data suggest that highly expandable I/S changed to slightly expandable I/S over a narrow temperature interval (10"-20~ Dif- ferences in the potassium availability from detrital components and in the K+/H § activity ratios of pore water do not appear to be related to the differences in the percentage of smectite layers of these I/S clays.
TL;DR: In this paper, the authors found that Na-smectite interstratification is due to the interaction of the positive charge of the interlayer cation repelling the hydrogens of the hydroxyl ions, one above and one below, closest to the inter layer space.
Abstract: The 001 spacing of Na-smectite was found to vary from 9.6 ,~ at 0% relative humidity (RH) to 12.4 ~ at 60-65% RH. The 9.6-,~ spacing corresponds to dehydrated Na-smectite, and the 12.4-,~ corresponds to Na-smectite with one water layer. A regular series of intermediate values resulted from ordered interstratification of the 9.6- and 12.4-~ units. Ordered interstratification was confirmed by the presence of a 001 spacing of 9.6 + 12.4 A = 22 A. This peak appeared under experimental conditions at about 35% RH. It appeared for calculated simulations of ordered stacking of 50/50 mixtures (_+ 10%) of 9.6- and 12.4-,~ units. The 004 peak of this 22-,~ spacing interacted with the 002 of the 9.6-A spacing of ordered mixtures of more than 50% 9.6-/k units and with the 002 of the 12.4-~ spacing of ordered mixtures of more than 50% 12.4-~ units. The result of this interaction was a complex peak, the position of which was a function of the ratio of 9.6- and 12.4-,~ units. This complex peak was noted for experimental and for calculated conditions. Calculated tracings assuming ordered stacking matched the experimental tracings closely, whereas those assuming random stacking did not. Ordering was apparently due to the interaction of the positive charge of the interlayer cation repelling the positive charge of the hydrogens of the hydroxyl ions, one above and one below, closest to the interlayer space. The collapse of a single interlayer space (dehydration) brought the interlayer cation closer to the hydrogens of the hydroxyls causing the hydroxyls to rotate such that the hydrogens shifted toward the adjacent interlayer spaces. Collapse of these two interlayer spaces was therefore more difficult. This same mechanism helps explain ordering in illite/smectite. The difference is that hydration/dehydration is quick and reversible, whereas the change from smectite to illite is slow and irreversible.
TL;DR: In this paper, X-ray powder diffraction (XRD) studies of the clay fraction of Upper Cretaceous mudstones from a shallow (2.5 kin) drill hole in the Niger delta indicate a high geothermal gradient (about 100~ km) during diagenesis.
Abstract: X-ray powder diffraction (XRD) studies of the clay fraction of Upper Cretaceous mudstones from a shallow (2.5 kin) drill hole in the Niger delta indicate a high geothermal gradient (about 100~ km) during diagenesis. The mineralogy of the clays is similar to that observed elsewhere and consists of interstratified illite/smectite (I/S), kaolinite, and chlorite. Detrital mica and K-feldspar are also present throughout the section. The composition-depth relationship of the I/S is different from that observed in deeply buried Gulf Coast shales. The Niger delta rocks show a linear change in composition of the I/S as a function of depth in the drill hole from 60 to 10% smectite layers. The I/S ordering is R=0 in shallower samples and progresses to R=I in deeper samples. The I/S in the deepest samples has R=3 ordering. No R=I I/S showing a first-order 27-)k XRD reflection was found. The Niger delta sequence differs from the Gulf Coast sequence by (1) a lack of R= 1 I/S showing a 27-,~ XRD reflection (which are common in Gulf Coast samples and contain 20% smectite layers), and (2) the existence of a simple, continuous linear relation between the composition of the R= 1 and R=0 I/S and depth. A comparison of composition-temperature curves for I/S formed under different diagenetic regimes shows different types of I/S ordering in which the presence of R= 1 I/S showing a 27-/k reflection and R=3 I/S types changes the composition-depth (and thus, composition-temperature) relations. These changes suggest a difference in the energy necessary to form the various ordering types. Also, geothermal gradient during burial appears to be responsible for different composition-temperature gradients found for the same type of I/S ordering.
TL;DR: In this article, a junction probability diagram is used to represent short-range and long-range ordered, random, and segregated interstratifications of mixed-layer clay minerals.
Abstract: Junction probability diagrams show variation in both composition and layer arrangement in mixed-layer clay minerals. These diagrams can represent short-range and long-range ordered, random, and segregated interstratifications. Mineralogical analyses ofillite/smectite from shale cuttings, bentonites, and hydrothermally altered tufts define characteristic reaction pathways through these diagrams. Shale and bentonite analyses fall along pathways joining smectite and illite on diagrams showing nearest- neighbor (R1) layer arrangements. Transition from random to Rl-ordered interstratifications occurs in shale samples containing 60-70% illite layers, and in bentonites containing 55-67% illite layers. Analyses of alteration products, however, fall near a line connecting rectorite and illite, which represents the maximum degree of R1 layer ordering. No mineralogical evidence is available to suggest that these alteration samples formed from a smectite precursor. All samples develop next-nearest (R2) and thrice- removed (R3) neighbor ordering along similar pathways. Transition to R2 ordering occurs gradually in samples composed of 65-80% iUite layers, and samples containing more than 85% illite layers may show strong R3 ordering.
TL;DR: In this article, the second derivative of absorbance and Munsell color designations were calculated from visible reflectance spectra obtained from the dry powders of nine hematites and 22 goethites.
Abstract: Nine hematites and 22 goethites were synthesized by a variety of methods to obtain monomineralic samples having a range of Al substitutions and particle sizes. The second derivative of absorbance and Munsell color designations were calculated from visible reflectance spectra obtained from the dry powders. Unit-cell dimensions, Al substitution, infrared band positions, mean crystallite dimensions (MCD) from X-ray powder diffraction, and particle size from fiber-optic Doppler anemometry (FODA) were determined. Previously reported correlations between Al substitution, goethite unit-cell dimensions, and OH-stretching and -bending band positions were confirmed. For hematite, the position of the second derivative peak at ≈600 nm was negatively correlated with Al substitution (r = −.86). Munsell value and chroma were positively correlated with Al substitution (r =.94 for both), but hue was not related to Al substitution. Hue appeared to become redder, however, as particle size measured either by FODA or MCD increased. For goethite, the position of the second derivative minimum at ≈485 nm was negatively correlated with Al substitution (r = −.99). Munsell hue appeared to be related to both Al substitution and MCD perpendicular to (110), MCD110, with hues becoming redder with increasing Al substitution and yellower with increasing MCD110. Correlations between Munsell value and chroma and parameters such as Al substitution, particle size, and OH-stretching and -bending band positions were poor, but goethites synthesized by oxidation of Fe2+ solutions at room temperature had higher chromas than goethites synthesized hydrothermally from an Fe3+ system. Visually determined colors agreed well with calculated ones. Second-derivative spectra and color designations calculated from visible spectra appear to be potentially useful for quickly estimating other properties of goethite and hematite, such as Al substitution and particle size.
TL;DR: In this article, a variable-rate leaching device was used to obtain sequential cation-exchange capacity (CEC) measurements from standard clays using a motorized screwjack and as many as 24 leaching tubes coupled to 60-ml plastic syringes.
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.
TL;DR: In this article, the reaction of smectite to illite in shale from the COST 1 well in the south Texas Gulf Coast and from altered ash-fall tuffs from the Morrison Formation in New Mexico was investigated using X-ray powder diffraction in conjunction with transmission electron microscopy.
Abstract: The reaction of smectite to illite in shale from the COST 1 well in the south Texas Gulf Coast and from altered ash-fall tuffs from the Morrison Formation in New Mexico was investigated using X-ray powder diffraction in conjunction with transmission electron microscopy. In the COST 1 well, the bulk of the detrital clay was originally a K+-deficient mixed-layer illite/smectite (I/S). As the I/S adsorbed K+ released by the dissolution of K-feldspar during burial, the proportion of expandable layers decreased with depth from ~65% near the top of the well to ~25% at 4500 m depth. In contrast, the proportion of low-charged structural planes [<0.8 eq per (Al,Si)4O10 unit] in the I/S decreased gradually from ~40% near the top of the well to ~15% near the bottom. Authigenic smectite with 100% expandable layers from the Morrison Formation tuffs is an alteration product of vitric ash. Where these tuffs have been buried to ~ 1400 m the smectite has reacted to form I/S with ~ 15% expandable layers. Direct lattice images of I/S crystallites from both locations reveal a correspondence between edge dislocations and the interface between illite layers and smectite layers. Al, Si, Fe, Ca, Mg, and Na were apparently mobile along these dislocations as the reaction of smectite to illite proceeded. Al was probably retained within the crystallite when illite layers replaced the smectite layers; however, some of the remaining cations were expelled. Lateral replacement of smectite layers by illite appears to have been the principal growth mechanism.
TL;DR: In this paper, multivariate statistical analyses of geochemical, mineralogical, and cation exchange capacity (CEC) data from a Venezuelan oil well were used to construct a model which relates elemental concen- trations to mineral abundances.
Abstract: Multivariate statistical analyses of geochemical, mineralogical, and cation-exchange capacity (CEC) data from a Venezuelan oil well were used to construct a model which relates elemental concen- trations to mineral abundances. An r-mode factor analysis showed that most of the variance could be accounted for by four independent factors and that these factors were related to individual mineral components: kaolinite, illite, K-feldspar, and heavy minerals. Concentrations of AI, Fe, and K in core samptes were used to estimate the abundances of kaolinite, illite, K-feldspar, and, by subtraction from unity, quartz. Concentrations of these elements were also measured remotely in the well by geochemical logging tools and were used to estimate these mineral abundances on a continuous basis as a function of depth. The CEC was estimated from a linear combination of the derived kaolinite and illite abundances. The formation's thermal neutron capture cross section estimated from the log-derived mineralogy and a porosity log agreed well with the measured data. Concentrations of V, among other trace elements, were modeled as linear combinations of the clay mineral abundances. The measured core V agreed with the derived values in shales and water-bearing sands, but exceeded the day-derived values in samples con- taining heavy oil. The excess V was used to estimate the V content and API Gravity of the oil. The log- derived clay mineralogy was used to help distinguish nonmarine from transitional depositional environ- ments. Kaolinite was the dominant clay in nonmarine deposits, whereas transitional sediments contained more illite.
TL;DR: In this article, the Mossbauer spectra of 15 hematites with Al substitutions between 0 and 10 mole % were taken at room temperature and X-ray powder diffraction indicated dimensions of these hematite in the c-direction to range upwards from 27 nm to crystals large enough to show no line broadening.
Abstract: Mossbauer spectra of 15 hematites with Al substitutions between 0 and 10 mole % were taken at room temperature. X-ray powder diffraction indicated dimensions of these hematites in the c-direction to range upwards from 27 nm to crystals large enough to show no line broadening. The Mossbauer spectra showed that magnetic hyperfine fields decreased both with increasing Al-for-Fe substitution and with decreasing crystal size. These relationships indicate that hyperfine field variations cannot, as has been done in the past, be unequivocally related to Al substitution alone. Hyperfine field reductions were paralleled by Mossbauer line broadening due to hyperfine field distributions. Only the hematites heated to 1000°C showed a significant variation of quadrupole splittings with Al substitution. No dependence of quadrupole splitting on crystal size was observed, indicating no detectable distortion of coordination polyhedra in the particle size range studied.
TL;DR: In this article, the clay and bulk mineralogy of soil and till from 26 Adirondack watersheds was studied and it was found that the clay fraction of the soils is composed predominantly of vermiculite, likely derived from the transformation of a mica precursor, and kaolinite.
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.
TL;DR: In this article, the authors used HRTEM to examine illite/smectite from the Mancos shale, rectorite from Garland County, Arkansas; illite from Silver Hill, Montana; Na-smectites from Crook County, Wyoming; corrensite from Packwood, Washington; and diagenetic chlorite from Tuscaloosa formation.
Abstract: HRTEM has been used to examine illite/smectite from the Mancos shale, rectorite from Garland County, Arkansas; illite from Silver Hill, Montana; Na-smectite from Crook County, Wyoming; corrensite from Packwood, Washington; and diagenetic chlorite from the Tuscaloosa formation. Thin specimens were prepared by ion milling, ultra-microtome sectioning and/or grain dispersal on a porous carbon substrate. Some smectite-bearing clays were also examined after intercalation with dodecylamine hydrochloride (DH). Intercalation of smectite with DH proved to be a reliable method of HRTEM imaging of expanded smectite, d(001) 16 A which could then be distinguished from unexpanded illite, d(001) 10 A. Lattice fringes of basal spacings of DH-intercalated rectorite and illite/smectite showed 26 A periodicity. These data support XRD studies which suggest that these samples are ordered, interstratified varieties of illite and smectite. The ion-thinned, unexpanded corrensite sample showed discrete crystallites containing 10 A and 14 A basal spacings corresponding with collapsed smectite and chlorite, respectively. Regions containing disordered layers of chlorite and smectite were also noted. Crystallites containing regular alternations of smectite and chlorite were not common. These HRTEM observations of corrensite did not corroborate XRD data. Particle sizes parallel to the c axis ranged widely for each sample studied, and many particles showed basal dimensions equivalent to > five layers. -J.M.H.
TL;DR: In this article, the structure and chemistry of rectorite are compared to those of true illite, and it is shown that the 20-A unit is compositionally centered on an interlayer bounded by two identical T-O-T layers each of which has compositionally different tetrahedral sheets.
Abstract: Alternating mica-like and smectite-like layers of rectorite give rise to periodically varying contrast in 10-A lattice fringes, yielding a periodicity of 20 A in a transmission electron microscopic study Expansion of rectorite using dodecylamine hydrochloride yields a three-layer repeat of thickness 32–35 A, consisting of a basic 20-A unit, identical to that in images of collapsed, dehydrated rectorite, and a 12-15-A thick, intercalated organic layer Thin packets of layers derived by grinding the sample are only 20 A thick, or multiples thereof Serrated edges of rectorite grains likewise have steps 20 A in height, implying that mechanical cleavage occurs readily along the weakly bonded, smectite-like interlayers The “fundamental” 20-A unit is proposed to be compositionally centered on an interlayer bounded by two identical T-O-T layers, each of which has compositionally different tetrahedral sheets Such structural considerations suggest that resultant 20-A units (“rectorite units”) are unique in structure and chemistry relative to true illite These results further imply that grinding and other treatment of coherent crystals of clay minerals may produce individual unit layers Moreover, when coupled with size-separation, such treatment may yield X-ray powder diffraction data that reflect reconstituted layer sequences
TL;DR: An X-ray powder diffraction study of a verrniculitized chlorite in an amphibole schist near Limoges, France, shows the following weathering sequence: chlorite ~ ordered interstratified chlorite/ vermiculite/VERMICAUS.
Abstract: An X-ray powder diffraction study of a verrniculitized chlorite in an amphibole schist near Limoges, France, shows the following weathering sequence: chlorite ~ ordered interstratified chlorite/ vermiculite ~ vermiculite. M6ssbauer spectroscopy indicates that vermiculitization proceeded by the release of ferrous iron from the 2:1 mica layer of the chlorite. The ferric iron content of the vermiculite product is almost the same as that of the initial chlorite. Infrared spectroscopy and chemical microprobe analyses show that Mg was preferentially extracted from the hydroxide sheet of the chlorite, whereas the Si and A1 contents progressively increased to the point of the formation of a pure dioetahedral alnminous vermiculite. The Si, A1, and Mg removal processes support currently accepted vermiculitization mech- anisms, but the behavior of Fe is slightly different. In this weathering sequence, vermiculitization does not appear to have taken place by the oxidation of Fe 2+, but rather, by the simultaneous leaching of Fe 2§ and Mg.
TL;DR: The < 1-μm fraction of 17 bentonite samples from Kinnekulle, southwest Sweden, were studied by chemical analysis, X-ray powder diffraction, and cation-exchange capacity as mentioned in this paper.
Abstract: The < 1-μm fraction of 17 bentonite samples from Kinnekulle, southwest Sweden, were studied by chemical analysis, X-ray powder diffraction, and cation-exchange capacity. The bentonites are interbedded with undeformed, flat-laying Ordovician and Silurian sediments and were formed by the transformation of volcanic ash (dated at about 450 Ma) into smectite, which later converted to mixed-layer illite/smectite (I/S). The reaction, possibly driven by heat from an overlaying diabase intrusion (about 300 Ma), stopped at different stages of conversion, as evidenced by the I/S which ranges in composition from 60 to 10% smectite layers. A 2-m-thick bed shows zonation, with decreasing smectite proportions towards the upper contact. The zonation is not symmetrical towards the lower contact. In thin beds the illite proportion is higher and the regularity of ordering is inversely proportional to the thickness of the bed. K:Sr and K:Rb ratios follow the illite pattern; the ratios are highest at the contact and in thin beds. The inhibiting effect of Ca and Mg on the smectite-to-illite conversion probably was the cause of less-reacted smectite in the center of the thick bed.