Thermal transformation of chrysotile from Uruaçu District, state of Goiás, Brazil, heated in dry conditions at temperatures from 600°C to 1300°C was studied by high resolution electron microscopy and selected area electron diffraction (SAD). Up to 600°C, no morphological or SAD pattern changes were observed. At 600°C, the fibrils were still crystalline with the characteristics of the clinochrysotile. In addition, a new fringe system of 10–15 Å spacings appeared sporadically parallel to the 7.3 Å fringes of chrysotile. Areas of these extra fringes seem to constitute favorable sites for the nucleation of forsterite. At 650°C, forsterite nuclei appeared inside the nearly amorphous fibrils in the shape of patches consisting of flaky crystallites. At 700°C the chrysotile structure had disappeared; the new spots present in the SAD pattern were indexed as those of forsterite. Between 800–900°C the crystallinity of the patches was clearly demonstrated. From the lattice images in the patches, topotactic relations between chrysotile and forsterite were analyzed. At 1000°C very tiny grains of enstatite were formed mixed with forsterite grains. The SAD pattern is complex due to the coexistence of forsterite, enstatite, and silica-rich amorphous areas. From 1100°C to 1300°C the tridimensional growth of enstatite was promoted. The present results support the topotactic relations between chrysotile and forsterite found by X-ray analysis although differences up to several degrees may exist when these phases are observed microscopically. Evidence suggesting a topotactic growth between forsterite and enstatite was also obtained.

The Antalya Unit, one of the allochthonous units of the Tauride belt, is of critical, regional tectonic importance because of the presence of rifting remnants related to the break-up of the northern margin of Gondwana during Triassic time. Paleozoic — Mesozoic sedimentary rocks of the Antalya Unit consist mainly of calcite, dolomite, quartz, feldspar, and phyllosilicate (illite-smectite, smectite, kaolinite, chlorite, illite, chlorite-smectite, and chlorite-vermiculite) minerals. Illite-smectite (I-S) was found in all of the sequences from Cambrian to Cretaceous, but smectite was only identified in Late Triassic-Cretaceous sediments. R0 I-S occurs exclusively in early-diagenetic Triassic—Cretaceous units of the Alakırçay Nappe (rift sediments), whereas R3 I-S is present in late-diagenetic to low-anchimetamorphic Cambrian—Early Triassic units of the Tahtalıdağ Nappe (pre-rift sediments). Kübler Index (KI) values and the illite content of I-S reflect increasing diagenetic grades along with increasing depth. Major-element, trace-element, rare-earth-element (REE), and stable-isotope (O and H) compositions were investigated in dioctahedral and trioctahedral smectites and I-S samples from the pre-rift and rift-related formations. Both total layer charge and interlayer K increase, whereas tetrahedral Si and interlayer Ca decrease from smectite to R3 I-S. Trace-element and REE concentrations of the I-S are greater in pre-rift sediments than in rift sediments, except for P, Eu, Ni, Cu, Zn, and Bi. On the basis of North American Shale Composite (NASC)-normalized values, the REE patterns of I-S in the pre-rift and rift sediments are clearly separate and distinct. Oxygen (δ18O) and hydrogen (δD) values relative to SMOW (Standard Mean Oceanic Water) of smectite and I-S reflect supergene conditions, with decreasing δ18O but increasing δD values with increasing diagenetic grade. Lower dD values for these I-S samples are characteristic of rift sediments, and pre-rift sediments have greater values. On the basis of isotopic data from these I-S samples, the diagenesis of the Antalya Unit possibly occurred under a high geothermal gradient (>35ºC/km), perhaps originating under typical extensional-basin conditions with high heat flow. The geochemical findings from I-S and smectites were controlled by diagenetic grade and can be used as an additional tool for understanding the basin maturity along with mineralogical data.

Analyses of samples of kaolinitic, illitic, and montmorillonitic clay materials exposed to artificial sea water for periods of six months to five years have yielded some evidence to support the contention that chloritic and illitic clay types may ultimately develop from montmorillonitic material in the marine environment. However, no indications of the initiation or induction of any major lattice alteration of the original kaolinite and illitic type structures have been recognized on the basis of the data collected.

The techniques of electron diffraction, electron microscopy, x-ray diffraction, and chemical analysis were employed to detect and measure the extent of modification of the clay materials at selected time intervals during the five year period.

Actual separations of illitic-like and chloritic-like materials from treated montmorillonitic material were accomplished by gravitational settling methods. Relative weight percents of 18.2 for chloritic clay separates and 4.4 for illitic clay separates were obtained after more than four years of treatment. Chemical analysis and electron microscopy data suggest that lattice alteration preceded the development of forty to seventy percent of the chloritic and illitic material separated.

The chloritic material apparently developed by initial formation of a magnesium-enriched montmorillonite having a hectoritic appearance. Subsequent development of threadlike extensions from the magnesium montmorillonite is shown by electron micrographs. These threads were observed to decrease or equilibrate in apparent amount within the chloritic separates as platelike forms began to appear after three years. The illitic separates were characterized by fine granulai material with increasing occurrence of larger platelike forms as exposure time increased.

The modification of montmorillonitic clay was observed to be more dependent upon the magnesium-potassium ratio in the sea water than upon the total salt concentration levels. The limiting magnesium-potassium ratio was found to be approximately 9.4 with a limiting low potassium concentration of 0.005 moles per liter for montmorillonitic material of less than 0.5 micron settling diameter. The alteration of the montmorillonitic material was noted only for material that was initially settled through the artificial sea water media. As the potassium concentration level of these media dropped by extraction below 0.005 molar, a bulk effect of the settling material became operative and the relative percent of altered material decreased.

Further, the relative amounts of modified material detected were decreased by the introduction of carbohydrate material into the sea water media. The amounts present after a definite time interval were also observed to be dependent upon the distributive tendencies of the source materials and the physical disturbance of the sea water media. Resuspension of the material by reagitation of the system decreased and significantly governed the rate of diagenetic modification.

Special electron micrographs are presented to illustrate relative stages of flocculation of montmorillonitic material as the ionic concentration of sea water increases. It is suggested that these stages govern to an appreciable extent the extent and rate of initiation of any ionic exchange and lattice changes that occur.

With the current interest in the use of transition metal-exchanged phyllosilicates as catalysts for novel organic syntheses, investigations into the factors which affect the movement of reactant, product, and solvent molecules into and out of their interlamellar region are of considerable importance. Mixed organic-water intercalates of a Wyoming montmorillonite, exemplified by the Na-montmorillonitepyridine-water system which can form four different intercalates exhibiting basal spacing of 29.3, 23.3, 19.4, and 14.8 Å depending on the pyridine: water ratio, have been used as a model system. X-ray and neutron diffraction and quasielastic neutron scattering data relating to the interconversion of interlayer species indicate that access to and exit from the interlayer space is hindered at high partial pressures of water by a water-film diffusion barrier in the interparticulate voids which exist between the aggregated silicate layers. At lower water vapor pressures the rate-limiting step for interconversion from one intercalate to another is the rate of transport of reagents and products to and from the clay particles. Under conditions where these rates are fixed, the rate-limiting step is the rate of diffusion of the pyridine molecule in the lower-spacing intercalate. Processes which involve a change in basal spacing do not necessarily proceed via a single discrete step, but are also affected by the amount of water made available to the system. In organic reactions catalyzed in the interlamellar space of various cation-exchanged montmorillonites (e.g., the conversion of alk-1-enes to di-2,2’-alkyl ethers and the reaction of alcohols to form ethers), rate-determining steps similar to those found above are likely to be operative. In particular, for reactions carried out in the liquid phase, where mass transport is facile and where phase-transfer problems are avoided, such reactions are likely to be diffusion controlled.

Mineralogical and geochemical variations among the Carboniferous and Cretaceous sedimentary kaolin deposits from Sinai provided an opportunity to examine the effect of the source area on compositions of the deposits. The Carboniferous kaolin deposits are mineralogically and geochemically heterogeneous. The Khaboba and Hasbar deposits consist of kaolinite, quartz, anatase, illite, chlorite, zircon, and leucoxene. The shale-normalized rare earth element (REE) patterns of the Khaboba deposit showed a slight LREE over HREE enrichment ((La/Yb)SN = 1.19–1.51) with a MREE depletion (Gd/Gd*SN = 0.51–0.75), while the Hasbar kaolin had a MREE enrichment. The Abu Natash kaolin deposit consisted of kaolinite, anatase, and a little quartz with larger TiO2, Cr, and V and smaller Zr and Nb contents compared to other Carboniferous deposits. The shale-normalized REE patterns of the Abu Natash deposit exhibited a positive Eu anomaly (Eu/Eu*SN = 1.28–1.40) and a MREE enrichment (Gd/Gd*SN = 1.41–2.05). The Cretaceous deposits were relatively homogeneous in terms of mineralogical composition and geochemistry and are composed of kaolinite, quartz, anatase, rutile, zircon, and leucoxene. The Cretaceous kaolin deposits showed mostly flat shale-normalized REE patterns with a variable LREE depletion.

The presence of illite and chlorite, the absence of rutile, large Zr and Nb contents, and the REE patterns suggested a component of weathered low-grade metasediments as a source for the Carboniferous deposits in the Khaboba and Hasbar areas, while the large Ti, Cr, and V, and small quartz contents indicated mafic source rocks for the Abu Natash deposit. The abundance of high-Cr rutile and the absence of illite and chlorite, and large Zr, Ti, Cr, and V contents suggested a mixture of medium- to high-grade metamafic and granitic rocks as source rocks for the Cretaceous kaolin deposits. The occurrence of alkaline rocks in the source of the deposits studied was identified by high-Nb contents and the presence of bastnaesite. The mineralogical and geochemical heterogeneity and lesser maturity of the Carboniferous deposits suggested local sources for each deposit and their deposition in basins close to the sources. The mineralogical and geochemical homogeneity and maturity of the Cretaceous deposits, on the other hand, indicated common sources for all deposits and their deposition in relatively remote basins.

Iron salts react readily with calcite in oxidizing calcareous environments to produce solid phase Fe-oxides. These reactions represent important processes in aqueous, geologic, and pedogenic environments. In the present investigation, Fe-oxides were precipitated from Fe(ClO4)2 solutions on undisturbed calcite grains in aqueous suspension. In this way it was possible to investigate the sequence of events in the crystallization process. Following an initial precipitation on the calcite grains, a period of slow growth of lepidocrocite was noted wherein 4-μm euhedral platelets formed with uniform orientation perpendicular to the calcite surface. The slow growth and highly crystalline nature of the Fe-oxide product may be partially due to the diffusion barrier formed by the growing oxide crystal mass which influenced rate of movement of HCO3− to the dissolved Fe phase and Fe ions and H+ towards the calcite surface. Upon continued aging, the supernate became noticeably opaque. As the suspended nuclei settled, new surfaces for crystal growth were provided which resulted in somewhat less crystalline lepidocrocite and goethite.

Thermally induced lamellar structure changes due to phase transition and degradation in organoclays based on a synthetic ‘Somasif’ mineral and two organic surfactants, di-methyl dihydro-ditallow ammonia chloride (DMDTA) and tri-butyl-hexadecyl phosphonium bromide (HTBP) were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, in situ simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) over the temperature range 30–280°C. Results indicated that the surfactant layer in ‘Somasif’-based organoclays underwent thermally induced melting-like order-disorder transition followed by desorption of surfactant molecules, resulting in drastic changes in the character of the layer periodicity. The transition temperature (Ttr), determined from the endothermic transition in DSC, was found to depend strongly on the type and the content of surfactant incorporated. Temperature-resolved SAXS indicated complex intercalated layered structures, containing multiple lamellar stack populations of two different organic layer thicknesses. A weak scattering peak (s0), located at exactly the half angular position of the strong first scattering maximum s1 (s0 = 0.5s1), was found in all tested ‘Somasif’ clays. The presence of this peak can be attributed to a slight breaking of the translational symmetry in the layered structure, causing the 1D repeat period in real space to be doubled. In other words, some portions of layers are grouped into pairs and a single pair forms the new repeat unit. This arrangement is reminiscent of the Peierls-like distortion.

A deposit of kaolin clay, the site of the General Zaragosa Mine, located about 50 km northwest of San Luis Potosi, S. L. P., Mexico, has produced more than 250,000 tons of refractory clay by room and pillar mining methods during the last 32 years. The clay was formed by hydrothermal argillation of part of a fault block of rhyolite flow-breccia and probably welded tuff, presumably lower Tertiary in age. A silica-rich gossan now exposed at the surface caps the clay deposit.

Samples collected sequentially from the fresh rock to the most highly altered kaolin and studied by optical, X-ray, DTA, and chemical methods, show progressively:

1. Bleaching of the breccia matrix accompanied by mobilization of much of the iron, which was concentrated locally as spots of reddish oxide in the least altered areas.

2. Mobilization, and removal of considerable alkali and alkaline earth metals, in excess of that required to form montmorillonite; mobilization of silica, which was redeposited as fine anhedral quartz crystals disseminated within the montmorillonite and associated kaolinite-halloysite, or developed tripolitic, argillized rock peripheral to the clay ore body.

3. Further desilication of the silica and clay yielding relatively pure, but poorly ordered, kaolinite-halloysite as the most intense end product of argillation. Much silica removed during intense argillation was reprecipitated as tripolitic clay, as minor cristobalite in microscopic globules and massive aggregates characteristic of colloform opal, and in vastly larger amounts as opal and chalcedony replacing the rock overlying the clay (forming a silica gossan).

4. Minor amounts of alunite are present at two places in the deposit, which are interpreted tentatively as being the most probable loci of rising solutions.

The influence of cation size on the misfit between the tetrahedral and the octahedral sheets of serpentine layers, and thus on the curvature of serpentine minerals, has been studied using an experimental approach, based on scanning and high-resolution transmission electron microscopies (SEM and HRTEM, respectively) coupled with analytical electron microscopy (AEM), and a theoretical approach, based on the elastic theory of thin plates and the surface stress concept.

Various Ni3(Si,Ge)2O5(OH)4 serpentine syntheses were prepared, with progressive tetrahedral substitution for Si by the larger Ge ion, the ratio Ge/(Si + Ge) ranging from 0 to 100%. Other parameters (temperature, time duration, water pressure) were fixed. From SEM-HRTEM observations and AEM analyses of all samples, two types of serpentine minerals were characterized: (1) curved structures of tubular or ‘roman-tile’ shape (curvature radius of 10 nm for 0% Ge, increasing with the Ge content), when the Ge tetrahedral content is <25%; (2) perfectly plane structures, with hexagonal or triangular shape (view normal to the layers), for greater Ge contents. These results prove the direct influence of cation size on the crystal curvature.

From a theoretical point of view, a single serpentine layer with a misfit between its tetrahedral and octahedral sheets can be considered as an elastic thin plate subjected to two different surface stresses, σ+ and σ−, on its two faces. The difference σ+ − σ− between these two surface stresses was calculated from the above geometrical misfit, and the curvature of the serpentine layer was related to σ+ − σ−, according to the elastic theory of thin plates. The calculated curvature radii, and the Ge content of transition from curved to plane structures, are in agreement with the above observed values. Curved serpentine crystals may then be considered as a stacking of such elastically curved single serpentine layers.

An organophilic bentonite was prepared by means of a reaction of natural Na-montmorillonite with trimethyldococylammonium which has an especially long n-alkyl chain. The addition of trimethyldococylammonium to montmorillonite was in the range 0.25–3.0 times the cation exchange capacity (CEC) of the clay (i.e. 0.23–2.82 mmol/g clay). The particle morphology in organic liquid suspensions of organoclay complexes was studied by measuring the viscosity based on Eyring’s rate process and Robinson’s relative sediment volume. In toluene, montmorillonite with 1.17 mmol/g clay trimethyldococylammonium (1.25 times the CEC) had the largest specific gel volume, relative sediment volume, and K-factor. The results of the stoichiometry for trimethyldococylammonium-montmorillonite show that practically all of the quaternary ammonium was adsorbed to montmorillonite. Maximum half widths of 001 reflections from X-ray diffraction patterns were obtained in the range 0.74–1.17 mmol/g clay, indicating a disordered arrangement of the organic cation molecules intercalated between the layers. Appreciable shifts to lower-frequency regions in the Fourier transform infrared absorption spectra as a result of CH2-stretching vibrations were observed with increasing amounts of the organic cation. When increasing the amount of organic cation added to the clay from 0.94 to 1.41 mmol/g clay, a large shift occurred to the lower-frequency side, approaching the frequency of the organic cation alone. This indicates that the interaction between adjacent hydrocarbon chains becomes progressively stronger, due to van der Waals attraction, with increases in the amount of organic cation. Interactions of the alkyl chains in trimethyldococylammonium-montmorillonite complexes with irregularly distributed and randomly arranged alkyl chains between the silicate layers were weak, and, as a result, solvation with external organic liquids occurred and gel formation developed through macroscopic swelling of the organoclay.

The morphology, dehydroxylation, and dissolution properties of single- and multi-metal (Cr, Zn, Cd, and Pb)-substituted goethites prepared using hydrothermal methods are reported. The crystal morphology varied with the nature and the number of metals present in the system. The presence of Cr produced broader crystals while Zn, Cd, and Pb produced narrower crystals than pure goethite. The presence of multiple metals retards the crystal growth of the mineral. Metal substitution caused changes in the unit-cell parameters and the infrared (IR) spectra of the samples. The IR spectra were also sensitive to the morphology of the crystals. The separation of γO and δOH bending frequencies increased with increase in area and aspect ratio of the (100) crystal face. The dissolution-kinetics studies (1 M HCl, 40ºC) of single-metal-substituted goethite provided the following dissolution rate order: Zn- > Pb(II)- ≥ Pb(IV)- > unsubstituted > Cd- > Cr-goethite. More complex results were obtained for the multi-metal-substituted samples. In the di-metal-substituted goethites, incorporation of Cr suppressed the dissolution rate of Zn-substituted goethite by 85% and Cd suppressed the dissolution rate of Zn-substituted goethite by 53%. Similarly, incorporated Cr and Cd suppressed the dissolution rate of Pb(II)-substituted goethite by 50%. The dissolution rates of multi-metal-substituted goethite were linearly related to the steric strains derived from the lattice parameters of the mineral. Dissolution studies also showed that Cr, Zn, Cd, and Pb(IV) were distributed homogeneously throughout goethite crystals while Pb(II) was enriched in the near-surface regions of the crystals. Incorporation of Cr and Pb(II) increased, while Zn and Pb(IV) decreased the dehydroxylation temperature of single-metal-substituted goethites. Incorporation of Zn suppressed the effect of Cr on the dehydroxylation temperature in multi-metal-substituted goethites.

The name volkonskoite was first used in 1830 to describe a bright blue-green, chromiumbearing clay material from the Okhansk region, west of the Ural Mountains, U.S.S.R. Since that time, the name has been applied to numerous members of the smectite group of clay minerals, although the reported chromium content has ranged from 1% to about 30% Cr2O3. The name has also been applied to some chromian chlorites. Because volkonskoite has been used for materials that differ not only in their chromium content but also in their basic structure, the species status of the mineral has been unclear.

To resolve this uncertainty, two specimens of volkonskoite from (1) Mount Efimiatsk, the type locality in the Soviet Union (USNM 16308) and (2) the Okhansk region in the Perm Basin, U.S.S.R. (USNM R4820), were examined by several mineralogical techniques. Neotype sample 16308 has the following structural formula:

$({\text{Ca}}_{0.11}{\text{Mg}}_{0.11}{\text{Fe}}^{2+}{\hspace{0.17em}}_{0.03}{\text{K}}_{0.02})({\text{Cr}}_{1.18}{\text{Mg}}_{0.78}{\text{Fe}}^{3+}{\hspace{0.17em}}_{0.29}\text{Ca}{}_{0.02})({\text{Si}}_{3.50}{\text{Al}}_{0.51}){\text{O}}_{10}{(\text{OH})}_2\cdot 3.64{\text{H}}_2\text{O}.$

Sample R4820 has the following structural formula:

$({\text{Ca}}_{0.25}{\text{Mg}}_{0.05}{\text{Fe}}^{2+}{\hspace{0.17em}}_{0.01}{\text{K}}_{0.03}{\text{Mn}}_{0.01})({\text{Cr}}_{1.07}{\text{Mg}}_{0.75}{\text{Fe}}^{3+}{\hspace{0.17em}}_{0.35}({\text{Si}}_{3.59}{\text{Al}}_{0.43}){\text{O}}_{10}{(\text{OH})}_2\cdot 4.22{\text{H}}_2\text{O}.$

Mössbauer spectroscopy indicates that 91% and 98% of the iron is present as Fe3+ in samples 16308 and R4820, respectively. X-ray powder diffraction patterns of both samples have broad lines corresponding to minerals of the smectite group.

On the basis of these data, volkonskoite appears to be a dioctahedral member of the smectite group that contains chromium as the dominant cation in the octahedral layer. Smectites containing less than this amount of octahedral chromium should not be called volkonskoite, but should be named by chemical element adjectives, e.g., chromian montmorillonite, chromian nontronite.

Rb-Sr and oxygen isotope studies, in addition to K-Ar isotopic determinations published previously, are reported on diagenetic and hydrothermal fundamental particles (particle thickness of 0.03 to 0.05 nm and particle ab size of 0.02–0.05 µm) of the East-Slovak Basin. The combined data set allows us to ascertain the crystallization conditions of the illite material from two bentonite units collected at two basinal sites located ~20 km apart, and characterized by prolonged diagenetic conditions induced by progressive burial. A bentonite rock characterized by a short hydrothermal event from the Zempleni mountains to the SW of the East-Slovak basin is also studied.

For the two first sites, the δ18O values increase in one case and decrease in the other, when the size of the diagenetic fundamental particles from bentonite samples increases. These variations suggest that temperature increased in one and decreased in the second of the two samples collected in the basin, while the particles were growing. In the case of the hydrothermal bentonite, the δ18O values of the different size-fractions consisting of fundamental particles remain about constant, suggesting constant temperature and fluid chemistry.

The Rb-Sr dates of the fundamental particles of the three bentonite rocks were systematically higher than the corresponding K-Ar ages. The 87Sr/86Sr ratios, which are initially involved in the particle nucleation, appeared higher than that of contemporaneous sea-water. In all cases, the initial 87Sr/ 86Sr ratio decreases when particle size increases, which implies supply of external Sr into the bentonite units. This external Sr seems to have had an 87Sr/86Sr ratio close or identical to that of the contemporaneous sea water. This means that Sr, probably of sea-water origin, progressively diffused from host shales into the bentonite units, during burial diagenesis. In turn it favors the suggestion made previously about diffusion of K from shales into the bentonite layers during illitization of the smectite from these units.

The crystallochemical features of Co in Co-substituted goethite solid-solutions prepared by two different procedures have been studied using infrared, X-ray photoelectron and electron energy loss spectroscopies. It was found that the path followed for the synthesis of Co-substituted goethite determines the oxidation state of Co in the goethite structure. Thus, in the solid-solution prepared by precipitation with Na2CO3 of an Fe(II) aqueous solution containing Co(II) cations, followed by the aerial oxidation of the precipitate, the Co cations were found to be divalent, whereas trivalent Co was incorporated into the goethite obtained by ageing a solution containing Fe(III) and Co(II) cations precipitated by the addition of KOH. This different behavior is explained by the higher pH of goethite formation in the latter case, which favors the oxidation of the Co(II) cations.

The thermal effects, as well as the survivability and origins of microorganisms in Cretaceous rocks, are evaluated from the timing and extent of the smectite to illite transformation in Cretaceous bentonites collected from cores outside the thermal aureole of the Pliocene Cerro Negro volcanic neck. Overall, randomly ordered mixed-layered illite-smectite (I-S) is the predominant clay mineral in these bentonites, and the K-Ar ages of I-S range from 36 to 48 Ma (21 analyses, two additional analyses were outside this range). Increased temperature from burial is thought to be the primary factor forming I-S in these bentonites. Kinetic model calculations of the smectite to illite transformation are also consistent with I-S formed by burial without any appreciable thermal effects due to the emplacement of Cerro Negro. In a core angled toward Cerro Negro, the percentages of illite layers in I-S from the bentonite closest to Cerro Negro are slightly higher (32-37%) than in most other bentonites in this study. The K-Ar ages of the closest I-S are slightly younger as a group (38-43 Ma; Average = 41 Ma; N = 4) than those of I-S further from Cerro Negro in the same core (41-48 Ma; Average = 44 Ma; N = 6). A small amount of illite in this I-S may have formed by heat from the emplacement of Cerro Negro, but most illite formed from burial. Vitrinite reflectance, however, appears to record the effects of heating from Cerro Negro better than I-S. Tentatively, the temperature of this heat pulse, based on vitrinite data alone, ranged from 100 to 125°C and this is most evident in the CNAR core. The upper temperature, 125°C, approximates the sterilization temperatures for most microorganisms, and these temperatures probably reduced a significant portion of the microbial population. Thermophiles may have survived the increased temperatures from the combined effects of burial and the intrusion of Cerro Negro.

The mineralogy of partially kaolinized strata interbedded with lignite at the San Miguel mine, Atascosa County, Texas, was investigated by X-ray powder diffraction and optical and scanning electron microscopy. The San Miguel lignite occurs in the lower Jackson Group (late Eocene) of southern Texas. Based on mineralogical and micromorphological data, some of these clay partings are probably volcanic in origin and were exposed to variable degrees of in situ kaolinization in a swamp environment. Coexistence of kaolinite, clinoptilolite, and opal-CT in several of these strata suggests that the partially kaolinized volcanic layers were subjected to a subsequent resilication process following burial. Kaolinite is the dominant mineral in the oldest and most kaolinized volcanic layer (underclay) below the lowest lignite bed (seam D). The kaolinite exhibits a well-developed vermicular morphology. The youngest volcanic layer, which occurs stratigraphically above the uppermost lignite seam, is characterized by pseudomorphs of volcanic glass shards and consists mainly of clinoptilolite. Movement of siliceous ground water from this layer to the underlying strata apparently provided silica-rich solutions from which opal-CT and large (as long as 300 μm) euhedral crystals of clinoptilolite precipitated in the fossilized plant roots, veinlets, and fractures within the underlying strata. Micromorphological relationships between the Sirich (opal-CT and clinoptilolite) and sulfide (marcasite and pyrite) minerals in the fossil roots and fractures suggest that the marcasite formed before and pyrite after the resilication process.

Quasi-spherical particles (7-µm mean diameter) were prepared from cross-linked hydroxy-Al-montmorillonite (basal spacing =15.3 and 18.6 Å) by spray-drying. These particles (SP-CLM) were used as a packing material for columns in high-pressure liquid chromatography (HPLC). Aromatic phosphate esters, chlorosubstituted phenyl-ureas, monosubstituted benzenes, and the o-, m-, and p-isomers of disubstituted benzenes were separated on the columns, using isopropanol and hexane. Alkyl and alkoxy groups in the solute molecules sterically hindered the interaction of these molecules with the solid phase. The retention of the isomers of disubstituted benzenes that possess one electronegative (or dipolar) and one nonpolar substituent increased in the order: o- < m- < p-. In contrast, for all investigated disubstituted benzenes containing two electronegative (or dipolar) substituents, the o-isomer was retained on the 18.6-Å SP-CLM more strongly than the m- and p-isomers. The chromatographic data suggest that the strength of the interaction of phenolic groups with the solid phase increased with the acidity of these groups. The o-isomers of phenols that contained an additional electronegative (or dipolar) substituent displayed an exceptionally strong adsorption. The capacity of the o-isomers of disubstituted benzenes containing two electronegative (or dipolar) substituents to form chelates with Al probably was responsible for the strong retention of such o-isomers compared with the retention of the corresponding m- and p-isomers.

Cross-linked hydroxy-Al-montmorillonite acted as a strong and selective adsorbent for many families of organic compounds. It was used successfully as the solid phase in HPLC separations with eluents ranging from nonpolar (e.g., hexane) to highly polar (e.g., water).

Solubility diagrams defined by log [Al3+] and log [H4SiO4] are given for hydrous alumina or aluminum silicate minerals which appear in bauxite, kaolin and pyrophyllite-diapore deposits. They are constructed based on thermodynamic data of relevant reactions both at the room temperature and at elevated temperatures.

An aqueous solution reacts to a mineral, in this case K-feldspar, and, by dissolving it, becomes saturated with respect to a certain mineral. This mineral begins to be precipitated and the solution changes its composition as a result of the precipitation as well as further dissolution of the original mineral. Then, it attains saturation with respect to another mineral, which is precipitated thereafter. Thus, different minerals are precipitated in turn.

The sequences of precipitation of minerals can be shown on the diagrams under different conditions. A sequence, aluminum hydroxide → kaolinite or pyrophyllite → silica mineral plus kaolinite or pyrophyllite is expected in a weakly acid solution. In contrast, a sequence, silica mineral → silica mineral plus kaolinite or pyrophyllite is expected in a strongly acid solution. The possibility of application of the sequence of precipitation thus expected to alteration zoning is also discussed.

KCl-, KBr-, and KI-kaolinite intercalation complexes were synthesized by gradually heating potassium-halide discs of the dimethylsulfoxide (DMSO)-kaolinite intermediate at temperatures to 330°C. Two types of complexes were identified by infrared spectroscopy: almost non-hydrous, obtained during thermal treatment of the DMSO complex; and hydrated, produced by regrinding the disc in air. The former showed basal spacings with integral series of 00l reflections indicating ordered stacking of parallel 1:1 layers. Grinding resulted in delamination and formation of a disordered “card-house” type structure. The frequencies of the kaolinite OH bands show that the strength of the hydrogen bond between the intercalated halide and the inner-surface hydroxyl group decreases as Cl > Br > I. The positions of the H2O bands imply that halide-H2O interaction decreases in the same order. Consequently, the strength of the hydrogen bond between H2O and the oxygen atom plane increases in the opposite sequence.

In the non-hydrous KCl-kaolinite complex the inner hydroxyl band of kaolinite at 3620 cm-1 is replaced by a new feature at 3562 cm-1, indicating that these OH groups are perturbed. It is suggested that Cl ions penetrate through the ditrigonal hole and form hydrogen bonds with the inner OH groups. In contrast, Br and I ions are too large to pass into the ditrigonal holes and do not form hydrogen bonds with the inner hydroxyls.