bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clay Alteration in Copper Deposits Associated with Granodiorites
Authors: Meyer Charles 
Published: August 2006

AbstractRecent development at deep levels in the Mt. Con Mine at Butte, Montana, has revealed a structurally early alteration type characterized by K-rich alkali feldspar, brown and green biotite, and 2M muscovite (sericite). This is similar to the K-rich biotite assemblage in numerous porphyry coppers as emphasized by Anderson, Gilluly, Creasey, and Rose. In Butte, and in some of the porphyry coppers, the assemblage is demonstrably earlier than the common feldspar-free, muscovite-quartz-pyrite assemblage which envelops pyrite-rich veinlets. On the other hand, few consistent mineral assemblages or detailed distribution patterns have yet emerged for argillic alteration, where illite, kaolinite, montmorillonite, and locally allophane and pyrophyllite are prominent phases. Probably much of the confusion results from extensive supergene alteration, though even this cannot be proved at present.In supergene and in hypogene alteration at least below 300°C, supersaturation of SiO2 in the aqueous phase may play an important role in determining alteration assemblages. Some reactions affected ar. (1) the hydrolysis of K-spar to K-mica. (2) albite to montmorillonite. (3) silica-rich illite or montmorillonite to kaolinite, an. (4) pyrophyllite to kaolinite.The encroachment of the sericitic zone on the argillic zone at Butte may be controlled by changes in ionic species of the veinward migrating SiO2 liberated by argillization of plagioclase. Within the sericitic zone and the veins, silica in solution is probably in equilibrium with quartz.
The Origin of High-Alumina Clay Minerals—A Review
Authors: Keller W. D. 
Published: August 2006

AbstractHigh-alumina minerals refer, in this paper, to Al-rich, normal sedimentary phases, including gibbsite, boehmite, diaspore, possibly “proto-diaspore” and “proto-alunite”, “Al-chlorite”, and corundum, in association with kaolin minerals. They may be derived from any common Al-containing rock. Processes of origin include direct bauxitization of non-clay silicate minerals and rocks, and the desilication of any of the common clay minerals, particularly of the kaolin group. Apparently aluminous gels were formed within certain marshy basins, and/or were transported into basins, giving rise to concretionary masses of high-alumina minerals. Concretionary deposits were formed by dissolution of Al and reprecipitation.Alumina is probably more soluble, inherently, than is interpreted from geologic occurrences. Even after Al is dissolved under appropriate pH, or complexing reactions, its solubility is obscured by Al-immobilization through fixation within 3-layer clay minerals, or absorbed by other phases. A 14Å phase, probably aluminous, is not uncommon in certain soils, and in flint and boehmite-diaspore-containing clays. Subtraction of silica by plants, is accompanied by concentration of alumina.
Genesis of Kaolinite from Montmorillonite by Weathering: Structural and Morphological Evidence of Transformation
Authors: Altschuler Z. S. , Dwornik E. J. , Kramer Henry 
Published: August 2006

AbstractKaolinite originating by the low-temperature subaerial transformation of montmoril-lonite occurs extensively in Tertiary clayey sands of central and northern Florida. It occurs in gray iron-stained weathering zones, as much as several feet thick, that transgress primary green clays of the Bone Valley and other formations over hundreds of square miles. Subjacent deposits of opal and chert, clearly post-depositional, are a widespread byproduct of the transformation.Kaolinization begins as a hexagonal modification of the edges of montmorillonite flakes. X-ray study reveals that montmorillonite degrades and disappears up-section, with the appearance of the 7.2 kaolinite reflection and a very small 20–21 Å reflection. The altered clay loses silica and gains alumina and water.The clay transformation apparently proceeds by intracrystalline leaching of tetrahedral silica layers by slightly acid ground water. Approximately regular interposition of resultant stripped packets within montmorillonite creates a regular 1:1 mixed-layered montmorillonite-kaolinite, which responds as montmorillonite does to glycolation and heating. The stripped kaoline-like packets develop hexagonal outgrowths of true kaolinite by lateral epitaxy. Nourished by the decomposing montmorillonite, the outgrowths enlarge and nucleate new vertical growth, observed as oriented crystallites, 40–50 Å thick.Transformation of montmorillonite to kaolinite is a major geochemical process: creating goethite-stained kaolinitic sands of regional extent, liberating much silica for chert deposition and ground-water enrichment, and constituting an eluvial process that leads, in some areas, to residual quartz sand plains.
High-Temperature Phase Development in Illitic Clays
Authors: Bohor Bruce F. 
Published: August 2006

AbstractFive illitic clays were treated with various inorganic cations and heated to over 1400°C in a high-temperature X-ray diffraction furnace.The illite lattice undergoes dehydroxylation from 475–600°C, and the resulting anhydrides begin to disappear at 850°C. The major high-temperature phases formed from untreated illites are β-quartz (1000–1300°C), spinel (1000–1400°C), and mullite (1150–1400 +°C). Minor amounts of cordierite, kalsilite, feldspar, corundum, iron oxide and forsterite may also occur with various adsorbed cations at temperatures above 1000°C. β-cristobal-ite was never observed in any of the runs, contrasting strongly with its prominent development among the high-temperature phases of montmorillonite.Certain adsorbed cations act as repressors of high-temperature phase development, while others seem to have the opposite effect. The order of decreasing repressive effect— K+> Na+> Li+> Ca+2> Mg+2> Be+2> Sn+2,4—also represents the sequence of increasing electronegativity and ionic potential of these cations. It is postulated that the degree of electronegativity and ionic potential of the adsorbed cations is proportional to the rapidity and degree of mullite crystallization, because of the influence of these factors in ion transfer and reaction product removal in the critical liquid phase at the clay mineral surface.
The Structure of Organic Montmorillonites and Their Adsorptive Properties in the Gas Phase
Authors: White D. 
Published: August 2006

AbstractPrevious work has shown that dimethyldioctadecyl ammonium montmorillonite is a very effective adsorbent in the gas phase for the separation of aromatic compounds from the paraffins, and for the separation of the disubstituted isomers of benzene. The present paper describes an investigation into this phenomenon.For this purpose a method of calculating entropies of adsorption from gas chromatographic data was derived, and results are given for relevant organic vapours adsorbed on the quaternary ammonium derivative, and on octadecyl ammonium montmorillonite. These results throw considerable light on the basis of the selectivity shown by the quaternary ammonium derivative, and a possible explanation of the mechanism is given.The effect of the method of preparation on the gas phase activity of this adsorbent is very large, and experimental work on the correlation of this with the structure of the derivative is described.
Electrokinetic Properties of Lime-Treated Bentonites
Authors: Ho Clara , Handy R. L. 
Published: August 2006

AbstractZeta-potentials of Na- and Ca-bentonites treated with varying amounts of Ca(OH)2were measured by a Northrop-Kunitz horizontal cell and non-polarizing Zn-ZnSO4electrodes. Influences of other factors such as particle size, clay concentration, and salt concentrations were also studied.The results indicate a four-stage change in zeta-potential and viscosity when Ca(OH)2is added in increasing amounts to Na-bentonite suspensionsIn the first stage, the addition of small amounts of lime caused no change in zeta-potential suggesting a counteracting effect of Ca++adsorbtion and reaction of OH-ions to increase the negative surface charge with only a slight change in viscosity. In the second stage, the addition of more lime resulted in a rapid decrease in zeta-potential accompanied by a rapid increase in viscosity and appearance of flocs. In the third stage, additional lime led to a slower decrease in zeta-potential but a continued rapid increase in viscosity and the formation of distinct large flocs. Apparently in all three stages the plentiful OH- ions caused dissociation of weakly acidic groups to provide additional negative sites for linking the clay particles by Ca++ ions. The dissociation of weakly acidic groups probably reached its full capacity by the end of the third stage, termed the “lime retention point”. In the fourth stage, the additional Ca(OH)2in excess of the lime retention point caused a slight change in zeta-potential and a slight decrease in viscosity. In this stage free lime was available for slow pozzolanic reaction.In the Ca-bentonite-Ca(OH), system, the first stage was an increase in zeta-potential due to dominant influence of OH-potential-determining ions. The second stage was a rapid decrease in zeta-potential and increase in viscosity, corresponding to the third stage in treatment in the Na+-clay. The end of the second stage is the lime retention point, after which excess lime is used for pozzolanic reaction.
Potentiometric, Electrical Conductance and Self-Diffusion Measurements in Clay-Water Systems
Authors: Gast R. G. , East Peggy J. 
Published: August 2006

AbstractPotentiometric measurements using commercially available cationic glass electrodes, electrical conductance and self-diffusion measurements of cations and water were made in electrolyte-free 3–5 per cent Li, Na, K, Cs, Ca and Sr bentonite-water systems and bi-ionic systems with varying ratios of K and Ca. Activation energies for conductance in the homoionic clays were calculated using the Arrhenius equation.The agreement between cation mobilities measured by diffusion and conductance indicates that the underlying mechanism is essentially the same for the two processes. But the activation energies for ion movement determined for conductance measurements do not explain the observed reduction in mobility. Only two clays, Li and Cs, gave values significantly higher than for the measured solution conductance and only the Cs clay gave a value higher than those calculated for ion conductance at infinite dilution.Increasing Ca saturation in K-Ca clays from 1 to 99 per cent increased the self-diffusion coefficient or mobility of K by a factor of about 1.7 and Ca by a factor of about 30 reflecting the effect of the predominate accumulation of the divalent cation in regions of highest negative potential. The reduction in activity of monovalent cations calculated from the potentiometric measurements, although of the same order of magnitude, was consistently less than the corresponding reduction in mobility in both the homoionic and bi-ionic clays. This difference became greater with increasing mobility of K in the bi-ionic clays.
Transformation of Clay Minerals by Calcium Hydroxide Attack
Authors: Diamond Sidney , White Joe L. , Dolch W. L. 
Published: August 2006

AbstractCalcium hydroxide was allowed to react with various clays, other silicates, and quartz at slightly elevated temperatures for several months. The reaction products were examined by X-ray diffraction, DTA, and electron microscopy, and were shown to be poorly-crystallized calcium silicate hydrates of the tobermorite family, and calcium aluminate hydrates. Quaternary phases were not detected, but some isomorphous substitution probably occurred. The extent of reaction was shown to be such that under appropriate conditions almost all of the clay mineral was decomposed. Electron micrographs of the reacted materials indicated that attack occurred from the edges of the particles, and in general the remaining unattacked portion of the clay did not suffer appreciable loss of crystallinity. It was postulated that the reaction involved progressive dissolution of the mineral at the edges of the particles in the strongly basic environment maintained by calcium hydroxide solution, followed by separate precipation of the reaction products.In these experiments the calcium silicate hydrate generated by the reaction between lime and quartz was uniformly calcium silicate hydrate gel (CSH (gel)); reaction with kaolinite and montmorillonite produced either CSH (gel) or calcium silicate hydrate (I) (CSH (I)) depending on the conditions of the reaction. At 60°C the alumina-bearing phase was tricalcium aluminate hexahydrate; at lower temperature the phase produced was a hexagonal material closely resembling 4CaO.Al2O3.13H2O (C4AH13) but retaining a constant 7.6Å basal spacing regardless of its state of wetness or dryness.It was found that under appropriate conditions the formation of CSH(I) resulted in as effective a cementation as did the formation of CSH (gel).
Cation-Exchange Constants for Clays from Electrochemical Measurements
Authors: Hanshaw Bruce B. 
Published: August 2006

AbstractIon exchange constants for various cations adsorbed on clays were determined using compacted-clay samples as membrane electrodes and theory for the membrane response of glass electrodes. The electrochemical cell used is conventionally written:

A static electrical potential is developed between the reference electrodes. The potential is a function of the cation species and of the cation activities in the two solutions and is given by an adaptation of the Nernst equation. From measurements of the electrical potential, the free energy of reactions or exchange constants for a series of reactions between various cation species were obtained. These determinations indicate that compacted clays prefer monovalent over divalent cations.Some exchange constants were determined for the same clays in a non-compacted state. Not only the magnitude but also the order of cation selectivity changed for the same clay when determinations were made in the dispersed state and compared with those obtained by electrochemical means using compacted clay. Publication authorized by the Director, U.S. Geological Survey.
Vermiculite Surface Morphology
Authors: Raman K. V. Venkata , Jackson M. L. 
Published: August 2006

AbstractA study of the surface morphology of vermiculites from several different sources by the electron microscope has indicated that, unlike the smooth surfaces of micas, the vermiculite surfaces show micromorphological structural variations such as small humps, prominent crystallographic steps on the basal cleavage planes, marginal rolling of the layers and layer buckling. The production of layer buckling may result from the inhomogeneity of interlayer population caused by the introduction of hydrated cations replacing potassium during weathering. The (110) steps on the surface of the cleavage can be observed and these are visualized as nuclei for weathering in addition to the particle edges.The surface morphology of vermiculites is closely related to the nature of the interlayer cation. When treated with potassium or ammonium salts, the surfaces assume smooth morphology, the K and NH4 ions occupying interlayer sites and collapsing the mineral. When treated with Na or Li salts, the complex surface morphology persists, and in some cases is enhanced, possibly by the slow exchange of residual potassium from the interlayer. On this basis, the presence of unweathered mica cores have been identified in natural vermiculites which show varying amounts of residual K2O content. It is possible to offer an explanation from structural considerations for the complex morphology of the vermiculite surfaces including the curling of the layers on depletion of potassium. The morphological features of vermiculites have been produced on biotite mica by leaching with salt solutions.
Clay Deposits of the Tuscaloosa Group in Alabama
Authors: Clarke Otis M. 
Published: August 2006

AbstractSediments of the Tuscaloosa Group, Upper Cretaceous Age, crop out in an arc that extends from North Carolina through the kaolin districts of South Carolina and Georgia, across Alabama, Tennessee, Kentucky and into southern Illinois. Deposits of clay, sand, and gravel were formed in a variety of geologic environments that include marine, lacustrine, lagoonal, fluvial and deltaic deposition. They accumulated on an eroded surface of pre-Triassic rocks.In eastern Alabama clay beds within the Tuscaloosa Group that occur close to the contact of the pre-Cretaceous crystalline rocks comprise detrital accumulations derived from saprolite, and consist of kaolinite, montmorillonite, chlorite and quartz. Clays occurring somewhat stratigraphically higher in this section are mixtures of illite, kaolinite, quartz and minor amounts of montmorillonite and chlorite.Westward in Alabama, clay in the Tuscaloosa Group occurs as thick irregular pockets and lenses of montmorillonite clay, whereas, in northwestern Alabama the clay is kaolinite with variable amounts of illite and montmorillonite. Some of the clay deposits in this area have been lateritized, resulting in the formation of bauxitic clay, which is a mixture of gibbsite and kaolinite.
NaOH Dissolution of Some Oxide Impurities from Kaolins
Authors: Langston R. B. , Jenne E. A. 
Published: August 2006

AbstractA working definition for allophane includes amorphous silica and alumina that are quickly soluble in boiling n/2 NaOH. Kinetic studies are used to differentiate and to make a rough estimation of the amount of allophane and certain other impurities present in some kaolin minerals.Solution rate studies on opal, gibbsite, two allophanes, volcanic ash, quartz, two halloysites, and two kaolinites are presented and in most cases the reaction rate orders with respect to the hydroxide treatment are determined. No interpretation of the observed rate orders are presented.The decomposition of the two kaolinites followed a third order rate law and their rate constants varied approximately by a factor of ten. The decomposition of the two halloysites followed a second order rate law and their rate constants varied approximately by a factor of five. It is not known why specimens of the same mineral species from different localities should have such large variations in their dissolution rates. Differences in their degree of crystallinity and the resulting surface area may be responsible.
Weathering and Transport of Sediment in the Cheyenne River Basin, Eastern Wyoming
Authors: Rolfe B. N. , Hadley R. F. 
Published: August 2006

AbstractThe weathering and fluvial transport stages of a sedimentation sequence of the Cheyenne River in Eastern Wyoming are discussed. The river heads in east-central Wyoming, crosses several rock units in its eastward path before reaching the Angostura Reservoir in southwestern South Dakota. The drainage area of the Cheyenne River above the Angostura Reservoir comprises about 9000 square miles.Weathering profiles of the rock units traversed by the river in this drainage area were sampled to determine their respective contributions to the sediment load. Among these formations are the lithologically diverse Chadron, Brule, Fort Union, Lance, Pierre, and Spearfish. The textural and mineralogical analyses of the weathered outcrops were compared with those of sediment samples collected at gauging stations operated by the Water Resources Division of the U.S. Geological Survey.X-ray diffraction studies of the weathered rock profiles and of the suspended sediment indicate a diverse clay mineral assemblage in the 2-1µ diameter size fraction. Kaolinite, illite, and vermiculite occur along with quartz and feldspar. However, the <1µ size fraction of the suspended sediment contained only montmorillonite. The kaolinite content of the 2-1µ size fraction of the suspended sediment increased in the direction of flow, at the expense of vermiculite and ilIite.The computed and observed amounts of sediment contributions by the various rock units show a fairly good fit; the data indicate the importance of defining mineral composition in terms of discrete size separates, cven under 2µ diameter. The increase in kaolinite content in the 2-1µ size fraction of the suspended sediment may be due to bank contribution downstream from the gauging stations. The montmorillonite content of the < 1µ size fraction is unchangcd by transport.
Kaolinite Stability in the Central Piedmont of Georgia
Authors: Grant Willard H. 
Published: August 2006

Abstract
A study of weathered profiles from fresh rock to the
surface in granitic rocks and biotite-plagioclase gneiss shows the
following: 1. The particle size of the kaolin increases from not subject to
estimate in fresh rock to a maximum of approximately 60
μ in the vicinity of the contact between the
B horizon and the saprolite, then it decreases to approximately 13
μ in the A horizon. 2. Gibbsite occurs most
abundantly when the abrasion pH of rock slurries is greater than 6 or less
than 5.5. In outcrop, gibbsite is abundant in the upper soil horizons and in
the partially weathered rock but is sparse in the intervening saprolite. 3.
The total amount of kaolin increases steadily upward from zero in fresh rock
to a maximum in the B horizon then declines sharply in the A
horizon.
These data are interpreted to mean that kaolin forms, grows and is
stable in saprock, saprolite and B horizon, but it is not stable in the
upper B and A horizons or in the very basic environment of incipient
weathering.
Interstratified Montmorillonite-Mica Clays from Subsoils of the Prairie
Provinces, Western Canada
Authors: Kodama H. , Brydon J. E. 
Published: August 2006

Abstract
Samples of glacial till and lacustrine soil clays
selected over a distance of 900 miles across the Canadian Prairie Provinces
were examined in detail by X-ray, chemical, thermal, infrared-absorption and
electron-microscope methods. All of the experimental evidence indicated a
marked similarity among the samples. The dominant component was an 18 Å
phase when glycerol-solvated, which was identified as a randomly
interstratified montmorillonite-mica. This was associated with minor amounts
of a 10 Å phase (randomly interstratified mica-montmorillonite), kaolinite
and quartz. Fourier transforms of the basal series of reflections gave
contents of expanded material (montmorillonite) near 55 per cent, whereas
calculation of the chemical formula gave near 80 per cent montmorillonite in
the interstratified component. The Fourier transforms confirmed the random
nature of the interstratification but also showed a tendency to zonal
segregation of the mica and montmorillonite layers. On the basis of the
chemical formula, the Greene-Kelly test and the infrared spectra, the
swelling layer composition was intermediate between that of beidellite and
that of Wyoming bentonite.
Although there were no large differences between the samples, the small
differences suggested two trends differentiating the till samples and the
lacustrine samples: (1) The proportion of the expanded component of the
interstratified mineral tended to be less in the lacustrine than in the till
samples. (2) The composition of the expanding layers in the lacustrine
samples tended to be nearer to the Wyoming bentonite composition than were
the till samples. These trends are likely related to K fixation during or
after deposition of the lacustrine materials, whereby the expanding layers
with a beidellitic composition would be pre-empted leaving layers more
similar to Wyoming bentonite.