Proportions Of Illite Research Articles

Chemical and Physical Properties of Paleozoic Potassium Bentonites from Kinnekulle, Sweden

The < 1-μm fraction of 17 bentonite samples from Kinnekulle, southwest Sweden, were studied by chemical analysis, X-ray powder diffraction, and cation-exchange capacity. The bentonites are interbedded with undeformed, flat-laying Ordovician and Silurian sediments and were formed by the transformation of volcanic ash (dated at about 450 Ma) into smectite, which later converted to mixed-layer illite/smectite (I/S). The reaction, possibly driven by heat from an overlaying diabase intrusion (about 300 Ma), stopped at different stages of conversion, as evidenced by the I/S which ranges in composition from 60 to 10% smectite layers. A 2-m-thick bed shows zonation, with decreasing smectite proportions towards the upper contact. The zonation is not symmetrical towards the lower contact. In thin beds the illite proportion is higher and the regularity of ordering is inversely proportional to the thickness of the bed. K:Sr and K:Rb ratios follow the illite pattern; the ratios are highest at the contact and in thin beds. The inhibiting effect of Ca and Mg on the smectite-to-illite conversion probably was the cause of less-reacted smectite in the center of the thick bed.

Pulverized-fuel ash for concrete: Compositional characterisation of United Kingdom PFA

Major oxide and component modal analyses show the composition of the pulverized-fuel ash produced over five days from each of 26 U.K. sources to remain virtually constant. Recurrent compositional differences do, however, exist between sources. These largely reflect different proportions of illite and kaolinite in the clay impurity of the coals burnt. Due to the fluxing action of K 2O, there is greater production of silicate glass (pozzolana) from illite than kaolinite. The molar ratio of potash to alumina (K/A) reflects the relative proportions of illite and kaolinite and is directly proportional to the concentration of pozzolana in PFA. It thus provides a Pozzolanic Potential Index (PPI) which allows compositional characterisation of PFA for use in concrete.

Kaolinite and mixed-layer illite–smectite in Lower Cretaceous bentonites from the Peace River coalfield, British Columbia

The X-ray diffraction analysis of 75 thin volcanic clay bands in the Lower Cretaceous of the Peace River coalfield shows kaolinite and mixed-layer illite–smectite to be the two clay minerals present. Kaolinite is dominant in the clay bands (tonsteins) in the coal-bearing Gething and Gates formations, whereas illite–smectite is dominant in the clay bands (K-bentonites) in the marine Moosebar Formation. A complete gradation exists between the two clay minerals, demonstrating their common volcanic origin. Volcanic textures are seen in thin section. The relationship between clay composition and depositional environment corresponds with the clay stability fields with smectite the precursor of the mixed-layer clay. The proportion of illite in the latter averages 22% and corresponds with the coal rank. The major-element analyses mainly reflect the clay composition but with contributions from resistate and diagenetic minerals. Amongst the trace elements there are those that are both immobile in the alteration process and diagnostic of a specific volcanic composition. Based on such trace elements the ash composition is thought to have ranged from rhyolite to dacite, perhaps due in part to original grain-size variation as in tephra beds.

THE MINERALOGY OF BRICKMAKING AT BROOMFLEET, NORTH HUMBERSIDE.

SUMMARY The mineralogy and chemistry of three clay raw materials and three types of brick product have been examined by transmitted light and scanning electron microscopy, X-ray diffraction and X-ray fluorescence analysis. The clays contain varying proportions of illite, kaolinite, vermiculite, quartz, calcite, rutile and hematite. The bricks consists of mullite, cristobalite, quartz, feldspars, spinel, rutile, illite and glass. The calcium-rich brick also contains wollastonite and gehlenite. Electron microprobe analyses of relict feldspars, new pyroxenes and matrix have been made, leading to an estimation of the glass composition. Examination of heated test pieces of each clay has shown the sequences of mineralogical change. This preliminary appraisal provides a basis for further work to elucidate the mineralogical reactions taking place in brickmaking.

Bentonites in the Chalk of central eastern England and their relation to the opening of the Northeast Atlantic

Within the post-Cenomanian Chalk sequence of central eastern England about 20 thin persistent marl horizons occur. These marls contain from 30 to 65% non-carbonate material the bulk of which is composed of a well crystallised Mg-rich smectite with a notable paucity of illite and quartz. The Chalk matrix above and below the marls contains up to 2.0% of non-carbonate matter which again is dominated by the presence of an Mg-rich smectite but which contains a larger proportion of illite and quartz than occurs in the marls. For both sets of non-carbonate materials the excellent crystallinity and Mg-rich nature of the smectite strongly suggest that it was formed by the in situ alteration of an aeolian transported volcanic ash, i.e. it is a true bentonite. Quartz and illite in the Chalk matrix are probably detrital components. Relative to a standard shale, non-carbonate materials from the Chalk marl horizons exhibit a highly anomalous trace element pattern with accentuated levels of Zr, Nb and Th but depleted levels of Ba, Rb and K. This trace element chemistry corroborates a volcanogenic origin for the smectite insofar as it is not explicable in terms of any realistic sedimentary process. The chemistry is best interpreted in terms of the magnetic processes responsible for the formation of the original ash precursor of the marls. It appears that this precursor had a pantelleritic composition and therefore originated from a source overlying an area where incipient continental rifting was taking place. Micromorphological examinations prove that residues from the Chalk marls contain small amounts of pyroclastic debris, including pumice and fragments of sideromelane glass. The morphology of the fragments suggests that the volcanic eruptions responsible for the ejection of the original ash into the air were of the shallow-water phreatomagmatic (Surtseyan) type. The distribution of marls in the Chalk of eastern England suggests that the ashfalls responsible for their origin were of the tropospheric type and were drawn by westerly winds from a centre to the west or northwest of mainland Britain. Of the numerous volcanic centres that lie in offshore areas to the west, the Anton Dohrn Seamount in the Rockall Trough appears to a likely centre of origin for the ashfalls. However, ashfalls responsible for the formation of the traces of smectite in the Chalk matrix were probably of the general background (stratospheric) type and may have been drawn from more distant centres. Volcanism at the Anton Dohrn Seamount was related to tensional effects in the continental crust that immediately preceded the formation of the Rockall Trough and the separation of Greenland from northwestern Europe during Tertiary times. Activity at the centre, and Cretaceous bentonites derived therefrom, therefore represent the earliest stages in the development of the Thulean igneous province.

Hydrothermal Alteration of a Serpentinite Near Takovo, Yugoslavia, to Chromium-Bearing Illite/Smectite, Kaolinite, Tosudite, and Halloysite

AbstractHydrothermal alteration products of serpentinite near Takovo, Yugoslavia, were studied by X-ray powder diffraction and chemical analysis. A zone of mainly blue clays adjacent to the hydrothermal vein contains intimately associated chromium kaolinite and tosudite at higher hypsometric levels and chromium halloysite(10Å) form at lower levels. A second zone of green clays contains principally illite/smectites, with predominantly illite layers nearer the first zone and smectite layers at greater distances. The potassium content diminishes as the proportion of illite layers diminishes. The composition of the smectite layers in the illite/smectite with the least proportion of illite is shown to be beidellitic. The mineralogical and chemical changes across the zone of alteration are interpreted in terms of two stages of alteration in which the second is more acidic than the first and is responsible for the inner zone of chromium-bearing kaolinite and tosudite and chromium halloysite.

Zur Feldspatverwitterung und ihrer Bedeutung für die Tonmineralbildung

Weathering of feldspars and their importance for the formation of clay mineralsIn quaternary sediments weathering and transformation of layer silicates, and in particular of biotites play a dominant role in the formation of clay minerals in soils of the moderately (semi) humid climate. In contrast, conflicting results were published concerning the participation of feldspar weathering for pedogenetic clay mineral formation. Another question is, whether formation of clay minerals in the fractions 0,6–0,2 μ m and&lt;0,2μ m by chemical weathering of micas and feldspars is the dominating process, or the formation of „pseudo clay minerals”︁ in the fraction 2–0,6 μ m by cryoclastic desintegration of micas and feldspars, as proposed by several authors. It is not yet clear, which clay minerals are formed from the weathering products of feldspars. — A necessary condition for a conclusive study of these problems is the vertical sedimentary homogeneity of the soil forming material.In eight loess soils investigated of very different genesis (a syrosem, chernozems, brown forest soils and a „braunlehm”︁) there were no indications for clay formation in the coarse clay fraction (2–0,6μm) by physical weathering of feldspars. This was also true for the loess‐syrosem of young Würm age, where the former climatic conditions should have promoted this process.In the chernozems, the brown forest soils and the braunlehm the proportion of illite and Smectite newly formed were about 25–40% and 45–50% respectively. They are derived mainly from layer silicates but also from feldspars. In the chernozems 15–20%, the recent brown forest soils 20–25%, in a brown forest soil from the last interglacial period more than 30% and in the braunlehm of middle pleistocene age more than 40% of the original feldspars were destroyed by chemical weathering and had participated in clay formation, especially in the formation of smectites.

Discussion of the age of the Ingletonian

D rs J. G. M itchell &amp; P. R. I neson write: We wish to bring to the authors’ ( O’Nions et al. 1973 ) notice K-Ar ages obtained from thirteen clay mineral separates from samples from five localities within the Ingletonian at Ingleton. These ages, summarized in the table below, show a range from 395 m.y. to 414 m.y. with a mean of 405 m.y. The analytical precision of all the data is better than ±2%. Unlike the authors, we observed no correlation between isotopic age and potassium content, nor was the presence of two components of minerals indicated by X-ray diffraction analyses of our samples. The range of potassium contents reflects only the proportion of illite over quartz in the samples. Our interpretation of the mean age of 405 m.y. with such small within site scatter is that it is a consequence of a well-defined thermal event experienced by the rock at this time (close to the Silurian–Devonian boundary). We contend that the spread of K-Ar ages from 419 m.y. to 451 m.y. reported by the authors is due to partial ‘overprinting’ of the age of isoclinal folding and major cleavage in the preAshgillian/Caradocian, by a period of refolding in Siluro-Devonian times, determined more precisely by our data at 405 m.y. It would appear that the response of the illite content of the rocks analysed admits the resolution of this later event better than do whole rock analyses. The authors have also obtained an excellent Rb–Sr isochron from whole rock Ingletonian

The Clay Mineralogy of the Haldon Gravels

AbstractThe less than 10 μm and less than 3 μm fractions of the heterogenous Haldon Gravels have been examined by X-ray diffractometry. Kaolinite of high to low crystallinity is the dominant clay mineral, with variable amounts of illite (clay mica) ; quartz, a little feldspar and anatase also occur. The kaolinite has been ranked using the crystallinity index of Hinckley and also by indices derived from the ratio of peak height to background height for the 10 and 11 peaks.Clay from the matrix of the psaphitic members of the Buller's Hill Gravel contains intermediate grade kaolinite with a little illite, but clay bodies included in this formation contain only low grade kaolinite with a high, but variable proportion of illite. The Tower Wood Gravel contains two distinct populations; one is identical to that of the Buller's Hill Gravel, the other consists of high crystallinity kaolinite with a little illite. Head Gravel formed from the Buller's Hill Gravel by solifluction contains intermediate to low crystallinity kaolinite.

Colloidal Soap as Proposed Primary Migration Medium for Hydrocarbons

Aqueous solution of hydrocarbons appears necessary to explain primary migration of liquid hydrocarbons in argillaceous source beds. However, relatively high solubility within the depth ranges of origin and primary migration (5,000-10,000 ft or more) is necessary to account for the known crude oil reserves. Colloidal soap greatly enhances hydrocarbon solubility, but its role has been questioned for several reasons: (1) lack of observations of micelles in the sedimentary section; (2) requirement of many times more soap than hydrocarbons for hydrocarbon solubilization; (3) problem of explaining the fate of the large quantities of soap required; (4) adsorption of soap on host rocks in specific cases; (5) doubt that soap concentrations in fluids at depth are sufficiently high for micelle formation; (6) conclusion by some authors that the more acidic, potentially soap-forming bitumen remains in source beds; (7) the extremely small interstitial pore spaces of fine-grained sediments, which constitute a mechanical barrier to micellar migration; and (8) an electrical barrier to migration due to n gative charges on both the ionic micelles and clay minerals. It is concluded that (1) search for micelles in presumed source beds has not yet been attempted; (2) a potential source of large amounts of soap exists in source beds; (3) after entering the reservoir, soap could be transformed to intermediate- and high-molecular-weight hydrocarbons and the asphaltenes and resins of crude oil; (4) relatively high temperature and electrolytic character of source-bed fluids at depth should promote solubility of soap; (5) soap concentrations in source-bed fluid should be sufficiently high for micelle formation; and (6) patterns with depth of organic elements (C, H, N, S, O, etc.), hydrocarbons, and acidic bitumen are compatible with soap formation. The most perplexing problems are the extremely small pore spaces and the electrical barrier in clayey source beds. Pore sizes are so minute that even the small ionic micelles and large hydrocarbon molecules would encounter difficulty in migrating during late compaction. The semi-permeable membrane effect on electrolytic fluids during late compaction apparently is caused by negative charges on closely spaced clay-mineral grains. Hence pore-to-pore migration of the negatively charged ionic micelles would be resisted. Clay mineral transformations, accompanied or followed by microfracture formation, perhaps could overcome these barriers. This postulate needs further testing by experimental and subsurface investigations. The large amounts of bitumen generated from kerogen contain high percentages of acid-enriched asphaltenes and resins. Known depth patterns of increasing amounts of asphaltenes and resins in organic matter, coupled with decreasing O+N+S content, could reflect, in part, a transfer of acids to interstitial waters by saponification. The higher the soap concentration, the larger would be the hydrocarbon solubilization capacity of each mole of soap present. Moderately high temperatures and release of bound water from clays should increase true solution of hydrocarbons which further enhances soap micelle formation. Transformation with depth of montmorillonite to increasing proportions of illite in mixed-layer clays should release additional saponifiable organic matter. Experiments demonstrate an adequate degree of hydrocarbon solubilization in concentrated soap solutions. Increases in salinity to above normal marine values progressively enhance micelle generation and hydrocarbon solubilization. Variations from brackish to well above normal marine salinities apparently exist at depth in marine source bed section. The accompanying moderately high temperature would promote transformation of the organic component, desorption of organic matter and water for migration, and decrease in micellar size. Eh, pH, and cation content of fluids in the major hydrocarbon migration depth intervals should be suitable for soluble soap formation. The low Eh is related to fine-grained character, clay content, and amounts and types of organic matter. In downdip Gulf Coast areas of Louisiana, pH is about 8.0, or between 8.0 and 9.0, at depths of several thousand feet and more. Calcium and magnesium cation concentrations are quite low and pore waters are of the sodium bicarbonate type. After source-bed fluids enter a reservoir system, several mechanisms could be responsible for breaking the soap colloid and freeing hydrocarbons. The most probable mechanisms are dilution of soap, decrease in pH, and increase in alkali-earth cation concentrations. If micelles persist until the moving reservoir fluid reaches a trap, the predominant mechanisms, triggered by water leakage into the caprock, would be increase in salinity, increase in calcium-ion concentration, and decrease in pH. Future research should assess the simultaneous effects of temperature, pressure, salinity, and other factors on micelle formation, hydrocarbon solubilization, and primary migration. Modeling should simulate subsurface conditions as closely as possible.