Offscraped strata within the toe of Nankai accretionary prism display an overall facies pattern of thickening and coarsening upward. Detrital clay minerals within the Quaternary trench-wedge facies are dominated by illite; chlorite is the second-most abundant clay mineral, followed by smectite. Relative mineral percentages change only modestly with depth. The hemipelagic clay-mineral population is virtually identical to clays washed from turbidite matrix, and different size fractions (<2 μm and 2–6 μm) show nominal amounts of mineral partitioning. Smectite content increases beneath the trench-wedge deposits, where the upper subunit of the Shikoku Basin stratigraphy (late Pliocene and early Pleistocene) includes abundance of volcanic ash. Syneruptive, subaerial chemical weathering of volcanic source rocks, together with in situ alteration of disseminated glass shards, caused the increase in smectite. Smectite begins a monotonic transformation to illite/smectite (I/S) mixed-layer clay at ~555 mbsf and an estimated temperature of ~65 °C. Ordered (R = 1) I/S interlayering first appears at ~1220 mbsf (<2 μm size fraction) and ~1100 mbsf (<0.2 μm size fraction). The illitization gradient coincides with a reduction in pore-water chlorinity, but depth-related changes in bulk mudstone geochemistry (K2O, Rb) are subtle. The absolute abundances of discrete smectite and I/S appear to be insufficient to account for the magnitude of pore-water dilution via in situ dehydration reactions. Instead, pore water probably was transported to Site 808, either from sources located deeper in the accretionary prism, where bulk mudstone porosities are lower, or from strike-parallel sources where mudstones originally deposited in the Shikoku Basin might contain higher percentages of smectite.

The structure of a highly disordered synthetic birnessite was studied by comparing powder X-ray diffraction (XRD) data with calculated patterns generated by BIRNDIF and WILDFIRE© in an attempt to describe the nature of disorder and to estimate the size of the coherent diffracting domains. The material has a turbostratic stacking sequence and coherent diffracting domains that are 25 to 30 Å on a side in the ab plane (N1 = 5 unit cells, N2 = 10 unit cells) and which average 2.5 unit cells thick parallel to c. Turbostratic stacking probably results because there are few constraints on the relationship between adjacent layers.

A model is presented to explain why tubular halloysite rolls in preference to tetrahedral rotation to correct misfit of the octahedral and tetrahedral sheets. It is shown that the rolling mechanism operates as it encounters significantly less resistance from Si-Si repulsion in comparison to tetrahedral rotation to correct the same amount of misfit. The model explains the observed and experimental rolling of planar kaolinites to form tubular halloysite upon hydration and exfoliation.

Continuous wave and pulsed electron paramagnetic resonance spectroscopies combined with thermal and chemical methods were used to identify and characterize V(TV), Fe(III), Mn(II) and Cr(III) in a multimineral system that consists of vermiculite and impurities of carbonates. All of these transition metals were structure-bound in mineral phases. The V(IV) was located in octahedral layers of the vermiculite and became oxidized to V(V) during the transformation of the host mineral to enstatite at about 800 °C. The Fe(III) was associated with the vermiculite as well as the carbonate impurities. The Fe(III) identified in the vermiculite was transferred into the enstatite structure during the thermal conversion. An indirect proof of Fe(III) and Cr(III) in the impurities was found in the heated samples in which these cations occurred in Ca and/or Mg oxides that were formed by transformation of the carbonates. The Mn(II) in the untreated samples was associated with the impurities and was also detected in oxides formed from the samples heated at 600 °C.

This paper deals with the use of Stern theory as applied to a clay-water electrolyte system, which is more realistic to understand the force system at micro level than the Gouy-Chapman theory. The influence of the Stern layer on potential-distance relationship has been presented quantitatively for certain specified clay-water systems and the results are compared with the Gouy-Chapman model. A detailed parametric study concerning the number of adsorption spots on the clay platelet, the thickness of the Stern layer, specific adsorption potential and the value of dielectric constant of the pore fluid in the Stern layer, was carried out. This study investigates that the potential obtained at any distance using the Stern theory is higher than that obtained by the Gouy-Chapman theory. The hydrated size of the ion is found to have a significant influence on the potential- distance relationship for a given clay, pore fluid characteristics and valence of the exchangeable ion.

The in-depth perturbation of vicinal water by the surfaces of montmorillonite layers was investigated by relating the swelling pressure, Π, of the montmorillonite layers to the H-O-H bending frequency, ν2, of the interlayer water. For this purpose, an oriented montmorillonite gel was deposited on a porous filter in an environmental chamber. On its underside the filter was in contact with a solution maintained at atmospheric pressure. By admitting nitrogen gas at a known pressure to the environmental chamber, water was squeezed from the gel into the solution until equilibrium was reached and Π equalled the applied pressure. Then the gel was divided into 2 parts. One part was used for the gravimetric determination of the water content, mw/mc. It was possible, therefore, to determine mw/mc as a function of Π. The other part of the sample was transferred to an FTIR spectrometer where the ν2 of the water within it was measured by attenuated total reflectance. Thus, the same samples were used to determine the dependence of both Π and ν2 on mw/mc. It was found that Π and ν2 were both exponential functions of mc/mw and so a linear relation was found between ln(Π + 1) and ln(ν2/ν2°), where ν2° is the H-O-H bending frequency of bulk water. These results strongly support the conclusion that the in-depth perturbation of the water by the surfaces of the montmorillonite layers is primarily responsible for both the development of Π and the departure of ν2 from ν2°.

The cation exchange capacities (CEC) and extractable cations in smectite, corrensite and palagonitized glass from hydrothermally-altered pillow lavas and hyaloclastite breccias were measured by both bulk wet chemical and in situ microanalytical techniques. Smectite has CEC's between 60 and 120 meq/100 g, palagonitized glass between 30 and 60 meq/100 g, and corrensite approximately 35 meq/100 g as determined by the in situ CsCl-exchange method. These experiments generally verify that Cs exchanges for those cations that are presumed (from the stoichiometry implied by microprobe analyses) to occupy interlayer sites in sheet silicates. Results of conventional CEC determinations are consistent with those determined by the in situ experiments: the individual microanalytical values for smectite and palagonitized glass bracket the bulk CEC values. The in situ experiments imply that Mg is the major extractable cation in smectite, Ca in corrensite, and both Mg and Ca in the palagonitized glass. We speculate that discrepancies between the equivalents of extractable cations predicted from elemental analysis and the equivalents of Cs sorbed may be due to the presence of charge-balancing protons that are not detected by the microprobe analyses. The sum of equivalents of cations extracted by NH4-acetate is about the same as the CEC determined by both the in situ and the bulk methods. Cation proportions indicated by NH4-acetate extractions from bulk samples are also generally consistent with the in situ results for all elements except Mg, which is a minor leachate of the NH4-acetate extractions in all the samples. To explain this discrepancy, we propose that 1) Mg may occupy structural sites within palagonitized glass, which inhibit its extraction by NH4 or Cs, and/or 2) there is a significant quantity of smectite, unsampled by the electron microprobe analyses, which contains insignificant interlayer Mg.

Nacrite, dickite and intermediate dickite-nacrite phases have been identified from the upper Paleozoic sequences of the Maláguide Complex (Betic Cordilleras, Spain). Nacrite developed as euhedral, pseudohexagonal or elongated crystals within sandstones and thin, irregular veins. Dickite developed preferently within extensive zones of fractures as very irregular, compact packets. Intermediate phases occurred in the sandstones and veins similar to the nacrite, or accompanying dickite. The mineral assemblage of the sandstones includes quartz-muscovite-kaolinite-type minerals, with or without albite, carbonates, chlorite and mixed-layers containing chlorite. The metamorphic conditions in which these minerals formed belong to anchizone, as can be deduced from the IC values. Dickite, nacrite and intermediate phases were studied by X-ray diffraction, infrared spectroscopy, differential thermal analysis and micros-copy. The results for dickite indicate a well-ordered mineral and agree with most of the published data. Conversely, IR spectra and DTA curves of nacrite show some differences in relation to the available data for this mineral. Based on the comparison with dickite and nacrite data, intermediate phases can be interpreted either as disordered varieties or as mixed-layered dickite/nacrite.

Ludox HS SiO2 sols at high concentrations show a peak in small angle x-ray scattering (SAXS) reminiscent to a “structure.” The appearance of such a peak was found to depend crucially on the thickness of the sample cell used for SAXS measurements. The thinner the cell used, the more prominent the peak. When the thickness was larger than 2 mm, it was no longer observable. When sols were treated with activated charcoal powders (in order to remove a surfactant) the peak became less prominent.

For the cases where clear features for structure were absent (thick sample regime), the Smoluchowski scheme was utilized to study the nature of sols. Namely, the distribution of the Smoluchowski species were estimated by numerically calculating the size distribution of particles directly from SAXS data. The distribution was found basically bimodal, and the main distribution peak, particularly for dilute sols (less than 5 wt%), was consistent with primary particles of SiO2. The second distribution peak was strongly dependent on the concentration of SiO2 particles. The observed trend was that the higher the concentration of SiO2 particles, the more prominent the second distribution peak and the locus of the maximum tended to move toward a smaller value in diameter. This behavior of the second distribution peak of the Smoluchowski species is no doubt a manifestation of the interparticle correlation. The observation of such behavior may provide a convenient means to characterize sols with interparticle correlation. This method was also applied for characterizing gels formed when the pH values were altered.

In Northwestern Mexico, the Miocene basins that disrupted the Sierra Madre Occidental Province are filled with sandstones and conglomerates (the Báucarit Formation) cemented mainly by zeolites of the heulandite-clinoptilolite group. Few volcanic tuffs are intercalated in the sediments for which four different groups of samples have been defined. These groups correspond to a gradation in the alteration of the glassy matrix. Group 1 is characterized by the preservation of the glassy matrix and the presence of disseminated patches of clay minerals with a continuous variation between aluminous Al-montmoril-lonite and ferric smectite end-members. Heulandite-group zeolites and opal C-T are also present. Group 2 is characterized by a nearly complete replacement of volcanic glass by a more homogeneous Al-montmorillonite. In some samples, heulandite-group zeolites are present as clusters on clay minerals. The primary vitroclastic texture is generally preserved and relict glass is present in small amounts. In group 3, the secondary assemblage is dominated by heulandite-group zeolite crystals as pseudomorphs of shards and pumiceous fragments. Discrete illite is present in all samples. Textures are exceptionally well-preserved. Group 4 is characterized by the presence of heulandite and clay minerals in which the Mg-Fe smectite end-member is more magnesian than in other groups. The original texture is not preserved.

The following are deduced from the mass-balance calculations: the alteration of the tuffs leads to a strong Mg- and Ca- and, to a lesser degree, Fe-enrichment, and to Na and K depletion. Zeolites account for Ca-enrichment and clay minerals are host for Fe and Mg. As a consequence, alteration may have occurred under open system conditions and the most likely source for the high Ca and Mg gains is a fluid circulating through the underlying volcaniclastic sediments and underlying mid-Tertiary volcanics of the bimodal (basaltic-rhyolitic) sequence. However, those fluids may have been rather dilute and weakly alkaline.

As estimated temperatures are between 85 and 125°C and as there is only a low burial, it is proposed that hot fluids are responsible for the alteration of volcanic glass. A decrease with time in the initial permeability of the tuffs is consistent with the observed evolution of the changing Al-smectite toward a more magnesian composition.

This report consists of a study of l-ornithine hydrochloride-vermiculite and of benzylammonium hydrochloride-vermiculite complex. The evolution of these organo-vermiculite structures upon heating is studied by X-ray diffraction (XRD) as well as infrared spectroscopy.

After heating vermiculite saturated with 1-ornithine cations, it shows condensation of interlayer ornithine molecules (peptide complexes). The stacking mode, opposing ditrigonal cavities, is not modified between aminoacid complex and peptide complex.

For vermiculite saturated with benzylammonium cations, the stacking sequence changes through heating by changing benzylammonium to NH4+. This transformation implies a sliding of the layers over each other. The ditrigonal surface cavities become face to face, as in the original mica. There are no random translations as in the starting complex.

Adsorption of Co2+ nitrilotriacetic acid (NTA) and equal-molar Co2+ and NTA by a low surface area (LSA) commercial gibbsite (3.5 m2 g−1) was investigated in batch as a function of pH (4.5 to 10.5), adsorbate (0.5 to 10 µM) and adsorbent (0.5 to 75 g L−1) concentrations and ionic strength (0.01 to 1 M NaClO4). The adsorption of Co2+ (Co-only) and the acid form of NTA (NTA-only) by gibbsite in 0.01 M NaClO4 exhibit cation-like and anion-like adsorption edges, respectively. For the equal-molar CoNTA chelate, Co and NTA adsorption edges were similar but not identical to the Co-only and NTA-only edges. Differences suggest the existence of a ternary CoNTA surface complex with the Co in the intact chelate coordinated to surface hydroxyls. NTA-only adsorption was insensitive to ionic strength variation, indicating weak electrostatic contributions to surface coordination reactions. This is consistent with the formation of inner-sphere surface NTA complexes and ligand exchange reactions in which monodentate, bidentate and binuclear NTA surface complexes form. Cobalt adsorption increases (edge shifts to lower pH by 1 pH unit) on LSA gibbsite as ionic strength increases from 0.01 to 1 M NaClO4. For the same ionic strength change, a similar shift in the Co-only edge was observed for another commercial gibbsite (16.8 m2 g−1); however, no change was observed for δ-Al2O3. Ionic strength shifts in Co2+ adsorption by gibbsite were described as an outer-sphere CoOH+ surface complex using the triple-layer model. Results suggest that, at waste disposal sites where 60Co and NTA have been co-disposed, NTA will not promote ligand-like adsorption of Co for acid conditions, but will reduce cation-like adsorption for basic conditions. Thus, where gibbsite is the dominant mineral sorbent, NTA will not alter 60Co mobility in acidic pore waters and groundwaters; however, NTA could enhance 60Co mobility where alkaline conditions prevail, unless microbial degradation of the NTA occurs.

The roles of molecular structure and charge are examined in the transport of cations within montmorillonite clay films. The series of Ru(NH3)63+, Co(NH3)3+, Co(en)33+, Co(sep)3+ and Co(bpy)33+ are examined in detail via electrochemical and spectrochemical methods. The electrochemical signal is enhanced both in minimizing the time required to develop the signal and in the magnitude of the signal for Ru(NH3)63+. In addition, the potential for the observed reduction peak is shifted negative and the current peak associated with reduction disappears with rinsing of the clay film. These observations are characteristic of a compound that is held by simple electrostatic charge characteristics. In contrast, the compounds Co(NH3)3+, Co(en)33+ and Co(sep)3+, while showing rapid and enhanced signal development, eventually evolve a signal that is diminished with respect to the bare electrode, consistent with a hydrophobic mode of retention. The signal for Co(bpy)33+ is slow to be observed, is diminished with respect to the bare electrode and is shifted positive in potential, all hallmarks of a strong, non-electrostatic mode of binding within the clay.

Aqueous suspensions of allophane show relatively high viscosity, presumably because of strong particle interaction between the unit particles. To test this hypothesis, we measured the particle weight and particle size of allophane during a dispersion using the light scattering method. The particle weight was more than several hundred times larger than that of the unit particle, and the size was 100–400 nm, whereas the Stokes’ diameter of the particles in the sample was less than 50 nm. Particle weight and size varied with the pH of the sample. Particle sizes were cross-checked by ultrafiltration through membrane filters. The experimental findings show that the unit particles of allophane within dilute dispersions appear to be associated like strings of beads, forming domains (primary floccules) about 100 nm in diameter. When these domains coagulate under certain conditions, they do not grow analogously but form clusters, such as secondary floccules, then precipitate. Formation of secondary flocculation of loose structure accounts for the maximum relative viscosity at the transition pH between dispersion and coagulation.

Seven Al-containing lepidocrocite samples, γ-Fe1−xAlxOOH, prepared from FeCl2/Al(N03)3 solutions with initial Al/(Al + Fe) mole ratios Ci of 0.0025, 0.01, 0.025, 0.05, 0.075, 0.10 and 0.15 mol/mol, were examined by means of Mössbauer spectroscopy at room temperature (RT) and at various temperatures in the range of 8 to 80 K. The spectra at RT and 80°K consist of broadened quadrupole doublets and were analyzed in terms of a single doublet and of a model-independent quadrupole-splitting distribution, the latter yielding the best fit. The observed variations of the quadrupole-splitting parameters with increasing Ci are inconclusive as to whether the Al cations are substituting into the structure. The temperature at which the onset of magnetic ordering is reflected in the spectra, was measured by the thermoscan method with zero source velocity. A gradual shift from 50 K for Ci = 0.0025 mol/mol to 44 K for Ci = 0.10 mol/mol was observed for that temperature. As compared to earlier studies of Al-free γ-FeOOH samples with similar morphological characteristics, the fractional doublet area in the mixed sextet-doublet spectra at 35 K is significantly higher for the present lepidocrocites. This observation is ascribed to the substitution of Al cations into the lepidocrocite structure. A similar conclusion is inferred from the variation with Ci of the maximum-probability hyperfine field derived from the spectra recorded at 8 K and fitted with a model-independent hyperfine-field distribution. The magnetic results suggest that for the sample corresponding to Ci = 0.15 mol/mol, not all of the initially present Al has been incorporated into the structure.

The dehydroxylation of a series of the kaolinite clay minerals, kaolinite, halloysite and dickite, has been investigated by Fourier transform in situ infrared emission spectroscopy over a temperature range of 100 to 800°C at both 50 and 5° intervals. Excellent correspondence was obtained between the high temperature emission spectra and FTIR absorption spectra of the quenched clay mineral phases. The major advantage of the technique lies in the ability to obtain vibrational spectroscopic information in situ at the elevated temperature. Dehydroxylation at a number of temperatures was determined by the loss of intensity of hydroxyl bands as indicated by intensity changes of the 3550 cm−1 to 3750 cm−1 emission spectra. As with all clay minerals, kaolinite clay mineral dehydroxylation is structure dependent. No clay phase changes occur until after dehydroxylation takes place. The kaolinite clay mineral loses the inner sheet and inner hydroxyl groups simultaneously, whereas dickite and halloysites are shown to lose the outer hydroxyls, as evidenced by the intensity loss of the ~3684 cm−1 peak, before the inner hydroxyl groups as determined by the intensity loss of the 3620 cm−1 peak. Evidence for a high temperature stable hydroxyl band at 3730 cm−1 for dickite and halloysite was obtained. This band is attributed to the formation of a silanol group formed during the dehydroxylation process. It is proposed that the dehydroxylation process for kaolinite takes place homogenously and involves 2 mechanisms. The dehydroxylation of dickite and halloysite takes place in steps, with the first hydroxyl loss taking place homogenously and the second inhomogenously.

To study the physico-chemical activity of lichens on micaceous components of granitic rocks, samples covered by thalli of Parmelia conspersa (Ehrht) Ach. and Aspicilia intermutans (Nyl.) Arn. were collected and examined with Scanning Electron Microscopy (SEM) equipped with a Back Scattered Electron (BSE) detector and an Energy Dispersive Spectroscopy (EDS) microanalytical system. The bio-physical activity of both lichen species leads to a deep alteration of biotite, which results in detachment, separation and exfoliation of biotite plates. Chemically, the bioweathering process of biotite in the lichenmineral contact zone involves considerable depletion of potassium (K) from interlayer positions in biotite and removal of several elements, corresponding to a 9.7% loss in matter. The sequence of the loss of elements is: K+ » Fetot > Ti4+ ≅ Mg2+. There are also some gains in the order: Ca2+ > Na+ » Al3+ > Si4+ attributed to dissolution of co-existing Ca and Na rich minerals. Geochemical mass balance results suggest the transformation of K-rich biotite to scarcely altered biotite interstratified with a biotite-vermiculite intermediate phase in the lichen bioweathered contact zones.

In an attempt to resolve the structure of opal-CT and opal-C more precisely, 24 opal samples from bentonites, Fuller's Earths, zeolite tuffs, biogenic silicas and silicified kaolins have been analyzed by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Results of this examination demonstrate that opal-C and opal-CT are part of a continuous series of intergrowths between end-member cristobalite and tridymite stacking sequences.

These findings are consistent with Flörke's (1955) interpretation of the most intense opal peak at ~4 Å as a combination of the (101) cristobalite and (404) tridymite peaks. The position and width of this peak are controlled by the relative volume of the two stacking types and the mean crystallite size. Direct evidence obtained by HRTEM provides data showing various stacking sequences in opals. Broadening due to crystallite size alone was determined by directly measuring crystallite size by TEM and comparing the measured size to the apparent size calculated using the Scherrer equation. XRD peak broadening is also described in terms of various contributions from structural disorder. The mean opal crystallite size ranges from 120 to 320 Å. For samples at either end of the size range, the crystallite size plays a larger role, relative to stacking disorder, in controlling peak broadening.

The retention of hazardous species, including many of the lanthanides, on soils and sediments is vital for maintaining environmental quality. In this study, high-resolution transmission electron microscopy (HRTEM) was used to identify surface precipitates of La and their degree of atomic ordering on oxides of Mn (birnessite), Fe (goethite) and Ti (rutile) over a pH range of 3 to 8. At pH >5.5, the aqueous concentration of La was fully depleted by all three metal-oxides. On birnessite, surface precipitation of La-hydroxide occurred at pH = 5 and appears to be the dominant sorption mechanism on this mineral. Surface precipitation was not observed on rutile or goethite until much higher pH values, 6.5 for rutile and 8.0 for goethite. Precipitation is thus correlated with the points of zero charge (PZC) of the minerals, 6.3 for rutile and 7.8 for goethite, and in each case was observed only at pH values above the PZC. Although La sorption was extensive on all of the minerals at the higher pHs, the depletion of La from solution by rutile and goethite at pH values well below the PZC indicates that the sorption mechanism differs from that on birnessite. While surface precipitation was found to be the dominant sorption mechanism of La on birnessite, surface complexation of monomelic or small multinuclear species appears to predominate in La retention on rutile and goethite at most commonly encountered pH values.

The response of two swelling clays (SWy-1 and SAz-1) and of one non-swelling clay (KGa-1) and of a series of mixtures of these clays to different electrolyte concentrations was examined using clay-modified electrode techniques. A non-interacting probe ion, Fe(CN)63−, was monitored via reduction for its arrival at a Pt electrode coated with thin films of the clay mixtures. The three clays had both different temporal responses and different equilibrium currents. For SWy-1 the currents were developed over time and were dependent upon the electrolyte of the bathing solution, which was consistent with X-ray diffraction data literature for the interlayer dimension. Similar behavior was found for SAz-1, but for KGa-1, currents were instantaneous and were independent of the bathing electrolyte. This suggests that the pores controlling the probe ion transport were between particle or pinhole in nature. When mixtures of the clays were examined, it was found that KGa-1 caused defects within the structures of the mixed clay films. The SWy-1 mixture was not as affected by these disruptions as was the SAz-1 mixture.