Some Results of the Study of Clay Minerals in the U.S.S.R.

Authigenic kaolin and illitic minerals during burial diagenesis of sandstones: a review

Abstract: The diagenetic evolution of kaolin and illitic minerals in sandstones is described here. The structural characterization of these minerals, the possible reaction pathways leading to their crystallization, and the origin of the fluids involved are discussed specifically. While early precipitation of kaolinite is in general related to flushing by meteoric waters, subsequent diagenetic kaolinite-to-dickite transformation probably results from invasion by acidic fluids of organic origin. Dickite is the stable polytype in most sandstone formations and the kaolinite-to-dickite conversion is kinetically controlled. The conventional model of kaolin illitization, assuming a thermodynamic control in a closed system, is discussed and compared to an alternative model in which illitization of kaolin is not coupled to dissolution of K-feldspar (Berger et al. , 1997). In the latter model, illite crystallization at the expense of kaolin implies that an energy barrier is overcome either by an increased K+/H+ activity ratio in solution or by a considerable temperature increase.

Scan electron micrographs of kaolins collected from diverse environments of origin; I

Abstract: Scan electron micrographs (SEM) show the textures of ball clay, plastic refractory clay, flint clay, and of kaolins from Cornwall, U.K., and Brittany, France. The texture of ball clay is a swirl and ragged-flake pattern. Plastic refractory clay shows a transition in texture from ball clay to plastic, semi-plastic, to semi-flint, and flint-clay. Flint-clay texture exhibits a matrix of tiny, compactly interlocked clay grains in which may be interspersed small, tight books and sheaves of kaolinite. The plastic to flint clays are interpreted to be sequential components of the flint-clay facies. In one sense they represent elements in clay diagenesis. Kaolins from the Cornwall district, U.K., and Brittany, France, show more similarity than dissimilarity in texture. Evidence from texture suggests that while hydrothermal action at Cornwall initiated alteration of the granite, the last significant process of kaolinization there was weathering.

Regional Fractures II: Fracturing of Mesaverde Reservoirs in the Piceance Basin, Colorado (1)

Abstract: Cretaceous strata in the east-central Piceance basin of northwestern Colorado were subjected to several phases of stress due to horizontal tectonic compression, burial, and uplift. These rocks contain a regional set of west-northwest extension fractures, observed in abundant vertical and deviated core from the U.S. Department of Energy's Multiwell Experiment and Slant Hole Completion Test wells. Time-depth relationships, fracture orientation, and fluid inclusion analyses indicate that the fractures formed at about 36-40 Ma, during a phase of increased Laramide west-northwest compression, and in a pressure-temperature regime compatible with the geologically reconstructed maximum burial depths. This regional fracturing is an example of load-parallel extension fracturing and basinwide dilatancy at depth, under conditions of high pore pressure and anisotropic, tectonically created, horizontal stress.

A chemical classification system for argillaceous sediments and factors affecting their composition

Abstract: Chemical analyses of clays, shales and slates from different parts of the world and from different sedimentological environments have been collected, together with analyses of the most common minerals found in these sediments. It is shown how these chemical compositions are distributed within a triangular diagram with the following molecular numbers in the corners: FeO (total iron)+MgO, Al2O3 and K2O + Na2O + CaO (does not include calcium present as carbonate). The most important factor influencing the composition of the sediments is weathering, while grain size has a relatively small effect. The influence of source rock is only noticeable as regards the most unweathered materials. On the basis of this triangular diagram a new classification system is introduced.

Controls on kaolinite and dickite distribution, Highland Boundary Fault Zone, Scotland and Northern Ireland

Abstract: Kaolinite and dickite occur widely in central Scotland and Northern Ireland. Stable hydrogen and oxygen isotope compositions of both minerals are similar, suggesting that the formation of kaolinite occurred first at temperatures of

Genetic Interpretation of the Polymorphism of the Kaolinite Group in Sedimentary Rocks

Abstract: SUMMARY The paper presents the dynamics of the structural change of kaolinite and its polymorphous (polytype) modifications at different stages of sedimentary rock formation. Sedimentogenesis is characterized by a gradual disordering of structure of triclinic kaolinite, the degree of disorder produced being proportional to the intensity and duration of the influence of the hydrodynamic medium. Epigenesis (deep) is connected with gradual transformation of kaolinite into dickite through the stage of mixed-layer growths inheriting the structure of twin rotations of disordered kaolinite from the sedimentogenesis stage. In metagenesis filling of fissures with dickite or nacrite takes place. The former is peculiar to the general thermodynamic medium of deep epigenesis/metagen-esis, whereas nacrite is an indicator of intense stress and seems to be due to transformation of dickite.

Colloidal ChemistryKapillarchemie, eine Darstellung der Chemie der Kolloide und Verwandter Gebiete. Herbert Freundlich

Abstract: and the fermentable substances. To BERTRAND we owe the introduction into science of the term oxidase. The adoption of this general term was based upon the discovery and characteristics of laccase and tyrosinase. The chapter concludes with a classification of oxidases and special reference to the sources, preparation, and characteristics of laccase, tyrosinase, aldehydase, and the purin oxidases. The third chapter is devoted to the peroxidases and catalases. The weight of opinion is inclined to the conception that peroxidases are substances capable of forming unstable peroxids from hydrogen peroxid, by double decomposition or by combining directly with the hydrogen peroxid to form unstable holoxid

The Geometrical Theory of Electron Diffraction and Analysis of Clay Mineral Diffraction Patterns

Abstract: In a crystalline substance, the material particles (atoms, ions, or molecules) are distributed in a regular manner, forming the crystal structure. In this structure, both the individual particles and their groupings alternate in three dimensions in such a way that their relative environments are the same throughout the structure. Thus, any arbitrary point in the structure corresponds to a multitude of other points, identical to it and arranged in a definite sequence which varies with the particular structure. Any of these sets of identical points having the same relative spatial arrangement is a characteristic feature for a given structure and, under the name of a space lattice, serves as a means of describing the structure.