Mixed-layer Type Research Articles

Anomalous patterns of clay minerals in fault zones

The anomalous enrichment of clay minerals in fault zones is considered a key factor affecting the seismic behavior of faults, fault permeability, and mineralization. This process also weakens the rock strength and triggers deformation, instability, and geological disasters. Nevertheless, the geological factors affecting the growth and anomalous enrichment patterns of clay minerals in fault zones are not systematically understood. In this study, the anomalous enrichment patterns of clay minerals within 220 natural faults are investigated (detailed information can be found in Appendix A). The main geological factors and processes affecting the anomalous enrichment of clay minerals in fault zones are revealed. The main formation modes and occurrence forms of the clay minerals in fault zones are investigated. The anomalous patterns of clay minerals in fault zones are classified into four categories and eight types, i.e., the felsic anomaly category (illite type and kaolinite type), mafic anomaly category (chlorite type), ultramafic anomaly category (smectite type, serpentine + talc type, vermiculite type, and palygorskite + sepiolite type), and argillaceous anomaly category (mixed-layer type). The 220 case studies include different types of faults and fault rocks. Thus, the results are promising for a wide range of engineering geological applications, e.g., analysis of fault activity and permeability changes and studying the genetic mechanisms of geological disasters near faults.

交代層構造を有するビスマス層状構造化合物Bi4.5Na0.5Nb2WO15の合成と粒子配向制御

交代層構造を有するビスマス層状構造化合物Bi4.5Na0.5Nb2WO15の合成と粒子配向制御

Transformation of coal mineral matter in relation to coal metamorphism in the Rajhara sub-basin, Daltonganj Coalfield, India

The nature and composition of silicate/clay minerals present in coals of the Rajhara sub-basin, India, and their changing pattern with progressive metamorphism is presented. Earlier studies had already revealed a remarkable range of metamorphism: the existence of a wide spectrum of coals varying in rank from 79% to 94% carbon level in the same seams within a distance of barely 600 m. In addition, higher rank coals, including semi-anthracitic and anthracitic ones (84–94% C), occur almost exclusively within an anticlinal zone. Outside of this zone the same coal seams contain only lower rank bituminous coals (79–84% C). Mineralogical studies of the associated silicate minerals of both the high and low rank coals have revealed a distinctive compositional pattern. The silicate minerals associated with the lower rank coals (exclusively situated outside the anticlinal zone) are mainly kaolinite, free silica and muscovite. Similar studies of higher rank coals, especially semi-anthracitic and anthracitic ones (which are the metamorphic products of the same low rank coals), indicate that a new phase of a three or mixed-layer type clay mineral is present in addition to the kaolinite, free silica and muscovite. The development of this new phase seems to be at the expense of the original kaolinite and free silica. It thus appears that the change in mineralogical composition of the Rajhara coals and its enhancement in rank are closely related to the conditions of metamorphism.

Motion of Fluid Particles in Perturbed Shear Flows

The motion of fluid particles in shear flows perturbed by unamplifying traveling sinusoidal waves is considered. The analogy between the formulation of the problem in terms of the stream function and the Hamiltonian dynamics is pointed out. An exact analytical solution is obtained for a perturbed mixing-layer type flow. For a perturbed wake type flow, an approximate analytical solution is obtained by employing the method of canonical transformation due to Hori.

Stability and the equilibrium selenium vapor pressure of the VSe 2 phase

Determination of the homogeneity range of the VSe 2 phase was made. It extends from V 1.01Se 2 to V 1.18Se 2 at 800°C and from V 1.04Se 2 to V 1.10Se 2 at 300°C. The selenium-rich limit of the adjacent monoclinic phase is about V 1.20Se 2 between 700 and 1000°C. The two-phase region between monoclinic and the VSe 2 phases extends from V 1.18Se 2 to V 1.25Se 2 at lower temperatures. Above 700°C, the mixture of two phases becomes a pseudosingle phase of a mixed-layer type. Equilibrium vapor pressures of selenium on the solid V x Se 2 ( x = 1.04–1.28) were measured by a quartz Bourdon gauge between 600 and 1000°C. Activities and other partial molar quantities were evaluated. Stability of the vanadium atoms in the CdI 2-like V x Se 2 phase was studied. A statistical model was applied for the nonstoichiometric V x Se 2 with the CdI 2-like structure. Vanadium atoms in the vanadium-rich layers are more stabilized than those in the vanadium-poor layers, and the differences between each stabilizing energy was about 20.0 kcal/mole.

A family of mixed-layer type bismuth compounds

Existence of a family of mixed-layer type bismuth compounds with the general formula Bi 4A 2m−1B 2m+1O 6m+9, where A is Na(1+), Sr(2+), Bi(3+), etc., B is Ti(4+), Nb(5+), W(6+), etc. and m is an integer as 1,2, or 3, was confirmed. Following new compounds, each of which has an orthorhombic cell, were found: Bi 5TiNbWO 15 and Na 0.5Bi 4.5Nb 2WO 15 for m=1, Bi 7Ti 4TaO 21, SrBi 6Ti 3Nb 2O 21 and BaBi 6Ti 3Nb 2O 21 for m=2 and BaBi 8Ti 7O 27 and PbBi 8Ti 7O 27 for m=3. An extensive study for thermal phase transitions was made by both DTA method and dielectric measurement.

Growth of complex single-crystal hexagonal ferrites

Numerous “mixed-layer type” hexagonal ferrites have been grown as crystals from molten flux. Two structural series both of which belong to ternary systems of the type BaO-MeO-Fe 2O 3 are differentiated. In the structural series M nY p, Me was Zn, Mg, Ni, Co, Fe, Cu, and Mn. The formation of a particular structure could not be correlated with Me, flux, composition or growth conditions used within the range that they were varied. A maximum in the frequency of occurrence of crystals with 46 layers could be accounted for statistically.

Problem of the thermodynamic status of the mixed-layer minerals

Minerals that show mixed layering, particularly with the component layers in random sequence, pose problems because they may behave thermodynamically as single phases or as polyphase aggregates. Two operational criteria are proposed for their distinction. The first scheme requires two samples of mixed-layer material which differ only in the proportions of the layers. If each of these two samples are allowed to equilibrate with the same suitably chosen monitoring solution, then the intensive parameters of the solution will be invariant if the mixed-layer sample is a polyphase aggregate, but not otherwise. The second scheme makes use of the fact that portions of many titration curves of clay minerals show constancy of the chemical activities of the components in the equilibrating solutions, suggesting phase separation. If such phase separation occurs for a mixed-layer material, then, knowing the number of independent components in the system, it should be possible to decide on the number of phases the mixed-layer material represents. Knowledge of the phase status of mixed-layer material is essential to the study of the equilibrium relations of mineral assemblages involving such material, because a given mixed-layer mineral will be plotted and treated differently on a phase diagram, depending on whether it is a single phase or a polyphase aggregate. Extension of the titration technique to minerals other than the mixed-layer type is possible. In particular, this method may be used to determine if cryptoperthites and peristerites are polyphase aggregates. In general, for any high-order phase separation, the method may be used to decide just at what point in this continuous process the system must be regarded operationally as a polyphase aggregate.

Mineralogical Problems of Intermediate Clay Minerals

AbstractOn the basis of mineralogical studies on many kinds of clay minerals found in Japan, the writers attach great importance to subtle variations in clay minerals and discuss them in the light of the concept of intermediate minerals. An intermediate mineral behaves partly as one mineral (say A) with certain treatments, and as mineral B under other conditions. There are two types of intermediate minerals: the deviation type and the mixed-layer type. The deviation type is homogeneous enough in its structure that we can describe it as composed of a combination of clearly different layer groups. The mixed-layer type has an interstratified structure of two or more kinds of layers. Furthermore it is suggested that each component layer of the mixed-layer type, in general, shows the properties of the deviation type. As an example of a mineral that can be discussed in light of the intermediate mineral concept, the writers describe the properties of very complex mixed-layer minerals related to mica clay minerals associated with epithermal ore deposits in Japan. Normally the mixed-layer minerals are found where there has been successive attack under different conditions of chemical environment or in an area that is transitional between two different chemical environments.Intermediate minerals in general are considered to be a mineral state (mineral configuration) modified in various degrees from an original mineral in response to successive changes of environmental conditions. The above viewpoints are supported by study of many clay specimens collected from alteration zones of epithermal ore deposits in Japan.It is considered that formation of intermediate minerals may be originated because of a latent defect structure in the original mineral. Polar character that is due to unequal distribution or ratio of the tetrahedral cations in a silicate layer may be favorable for the formation of the regular mixed-layer structure. Finally, intermediate minerals may be arranged according to the following scheme: Mineral A—deviation type of mineral A—mixed-layer mineral A-B—deviation type of mineral B—mineral B.