Iron-rich Montmorillonite Research Articles

A full factorial design for the decolorization of real textile wastewater using iron-rich montmorillonite by sonocatalytic process

In this study, the sonocatalytic process was used to remove colour from the effluent of a textile factory located in Turkey. Clay from a brick-tile factory located in the city of Eskisehir was used to enhance the effect of ultrasound (US) at 20 kHz frequency and 750 W power. The structure, morphology and composition of the clay were identified by characterization studies including FT-IR, XRD, XRF, SEM and TGA. The clay consists mainly of montmorillonite and iron-rich montmorillonite as smectite minerals, nontronite, quartz minerals, calcite and dolomite as minor clay minerals. In the scope of the study, Design of Experiment (DoE) and a Full Factorial Design (FFD) was used to determine the operating conditions that affect the color removal efficiency of textile industry wastewater. pH, clay amount, time, and H2O2 concentration were determined as critical factors using Analysis of Variance (ANOVA). It has been confirmed that when the critical factors for color removal efficiency—specifically, a pH of 2. 2 grams of clay, a duration of 120 minutes, and 35 ppm of H2O2—are kept constant, the resulting removal percentage was predicted as 94% approximately by using regression model. The optimal levels of factors have been verified by the validation experiments.

Photocatalytic decolourization of the X3B textile dye in aqueous solutions using iron-rich montmorillonite

Photocatalytic decolourization of textile dye X3B in aqueous solutions was investigated, using iron-rich montmorillonite (MMt, 2·24%Fe2O3) under a 15 W low-pressure UV lamp (λ = 254 nm, I = 48·4 μW/cm2). Hydroxyl radicals (•OH) were detected by tert-butyl alcohol (TBA) in aqueous MMt suspensions under UV irradiation and were found to be responsible for the degradation of X3B. Free iron ions dissolved in MMt suspensions, structural iron in the MMt solid, and the charged surface of nano clay are responsible for hydroxyl radical (•OH) production. Low pH values are favorable for the decolourization of X3B. The •OH concentration increased with increasing aqueous MMt concentrations in the range of 0 – 2·0 g/L; higher concentrations, for example, 5·0 g/L MMt, inhibited the •OH production. The addition of oxalate was favorable for X3B photodegradation in acid-washed MMt suspensions. This study shows that iron-rich MMt is a potential photocatalyst for the treatment of dye wastewater.

Conditions and mechanism for the formation of iron-rich Montmorillonite in deep sea sediments (Costa Rica margin): Coupling high resolution mineralogical characterization and geochemical modeling

Iron-rich smectite is commonly described in the diagenetic fraction of deep-sea sediment, as millimeter to centimeter aggregates dispersed in the sediment, or as a coating on sedimentary particles or nodules. This study examines several factors to elucidate formation mechanisms of a particular iron-rich smectite and its potential transformation to glauconite. The study combines a detailed mineralogical investigation on natural samples and a chemical modeling approach to assess mineralogical reactions and pathways. Transmission electron microscopy (TEM) observations and analytical electron microscopy (TEM–AEM) analyses were conducted on microtomed samples of millimeter- to centimeter-long green grains. These grains are widespread in pelagic calcareous sediment from the Costa Rica margin. They are composed of pyrites that are partially dissolved and are surrounded by amorphous or very poorly crystallized iron-rich particles. Iron-rich montmorillonite grows from an amorphous precursor and its formation requires the input of Si, O, Mg, K, Na and Ca; our results suggest that these inputs are supported by the dissolution of sedimentary phases such as volcanic glasses, siliceous fossils and silicates. Thermodynamic modeling of fluid–sediment interactions was conducted with the geochemical computer code PhreeqC, using mineralogical and pore fluid compositions from sediment samples and calculated estimates for thermodynamic constants of smectites that are not maintained by the computer code. Simulations confirm the possibility that the green grains are the product of pyrite alteration by seawater under oxidizing conditions. The extent of smectite production is controlled by the kinetics of pyrite dissolution and fluid migration. The absence of aluminum in the Costa Rica margin system explains the formation of an iron-rich montmorillonite instead of glauconite, whereas the presence of calcite that buffers the system explains the formation of an iron-rich montmorillonite instead of iron oxides.

PHOTOCATALYSIS BY IRON-RICH MONTMORILLONITE FOR THE TREATMENT OF DYEING WASTEWATER

This study investigates the photocatalytic degradation of dyeing wastewater by iron-rich montmorillonite (MMt) under a 25 W low-pressure mercury lamp (λ = 254 nm, I = 48.4 μW/cm2). Exposing MMt to UV irradiation worked to catalyze the photobleaching of wastewater used in the dyeing process. COD removal efficiencies of 65.0% and 74.0% were achieved in 1 g/L MMt suspensions at a pH of 3 in the absence and presence of 30 min of UV irradiation, respectively. A decolorization efficiency of 71.4% was reached with 1 g/L MMt suspensions at a pH of 3 after 30 min of UV irradiation, while only 4.9% decolorization was attained in darkness. These results indicate that iron-rich MMt is a good photocatalyst for decolorization and COD removal in wastewater from dyeing processes. A low pH value is beneficial to the decolorization of dyeing wastewater. A preliminary photocatalytic mechanism is proposed: the iron in the MMt is responsible for the decolorization of the wastewater because it produces a highly oxidative species of hydroxyl radicals (•OH).

Photocatalytic decolourization of the X3B textile dye in aqueous solutions using iron-rich montmorilloniteA paper submitted to the Journal of Environmental Engineering and Science.

Photocatalytic decolourization of textile dye X3B in aqueous solutions was investigated, using iron-rich montmorillonite (MMt, 2.24%Fe2O3) under a 15 W low-pressure UV lamp (λ = 254 nm, I = 48.4 μW/cm2). Hydroxyl radicals (•OH) were detected by tert-butyl alcohol (TBA) in aqueous MMt suspensions under UV irradiation and were found to be responsible for the degradation of X3B. Free iron ions dissolved in MMt suspensions, structural iron in the MMt solid, and the charged surface of nano clay are responsible for hydroxyl radical (•OH) production. Low pH values are favorable for the decolourization of X3B. The •OH concentration increased with increasing aqueous MMt concentrations in the range of 0 – 2.0 g/L; higher concentrations, for example, 5.0 g/L MMt, inhibited the •OH production. The addition of oxalate was favorable for X3B photodegradation in acid-washed MMt suspensions. This study shows that iron-rich MMt is a potential photocatalyst for the treatment of dye wastewater.

Photocatalytic Degradation of Orange II in Aqueous Iron-Rich Montmorillonite Solutions

In this work the photodegradation of orange II was carried out in the presence of iron-rich montmorillonite (MMt) (2.24% Fe2O3) using a 15-W low-pressure ultraviolet lamp (λ=254 nm, I=48.4 μW/cm2). The effects of pH, MMt dose, and dye concentration were studied. A low pH value is favorable for the decolorization of orange II. The hydroxyl radical (O•H) concentration increased with increasing concentration of MMt in aqueous solutions in the range of 0–1.5 g/L. Concentrations higher than 5.0 g/L MMt inhibited the O•H production. There was no significant decrease in photocatalytic activity when the catalyst was reused. Hydroxyl radicals were detected by tert-butyl alcohol in aqueous MMt suspensions under ultraviolet irradiation and were responsible for the degradation of orange II. Free iron ions dissolved in MMt suspensions, structural iron in the MMt structural and the charged surface of nanoclay are responsible for the hydroxyl radical (O•H) production. Free iron ions dissolved in solution plays a predominant role in the degradation of orange II. This study shows that iron-rich MMt is a potential photocatalyst for dye wastewater treatment.

Photochemical formation of hydroxyl radicals catalyzed by montmorillonite

In this work, the photooxidation of benzene and the formation of phenol in aqueous suspensions of the iron-rich montmorillonite under irradiation of a 250 W metal halide lamp ( λ ⩾ 365 nm) were investigated. We confirmed that hydroxyl radicals ( OH) were produced by illuminating montmorillonite and was responsible for the photooxidation of benzene in aqueous suspensions of montmorillonite. Low pH value facilitated the formation of hydroxyl radicals in the pH range of 2.0–10.0. The OH concentration increased with increasing the concentration of montmorillonite in aqueous solutions in the range of 0–20.0 g l −1. Higher concentration like 25.0 g l −1 montmorillonite inhibited the OH production. Iron, predominantly free iron in the clays, is believed to be one of the most important factors determining OH formation. Structural irons in montmorillonite have contributions to OH formation, especially in the presence of carboxylate ions. The formation of OH from montmorillonite under irradiation of near UV and visible light indicates that clays might play important role not only in transfer through adsorption but also in transformation through oxidation of organic compounds on the surface of clay particles in air, water, soil or even top sediments.

Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars

Mixtures of a Hawaiian palagonite and an iron-rich, montmorillonite clay (15.8 ± 0.4 wt% Fe as Fe 2O 3) were evaluated as Mars surface spectral analogs from their diffuse reflectance spectra. The presence of the 2.2-μm absorption band in the reflectance spectrum of clays and its absence in the Mars spectrum have been interpreted as indicating that highly crystalline aluminous hydroxylated clays cannot be a major mineral component of the soil on Mars. The palagonite sample used in this study does not show this absorption feature in its spectrum. In mixtures of palagonite and iron-rich montmorillonite, the 2.2-μm AlOH clay lattice band is not seen below 15 wt% montmorillonite. This suggests the possibility that iron-rich montmorillonite clay may be present in the soil of Mars at up to 15 wt% in combination with palagonite, and remain undetected in remotely sensed spectra of Mars.

Iron Substitution in Montmorillonite, Illite, and Glauconite by 57Fe Mössbauer Spectroscopy

AbstractThe 57Fe Mössbauer spectra of an iron-rich montmorillonite, an illite, and two glauconites were measured and computer-fitted with appropriate Fe3+ and Fe2+ doublet resonances. The broad experimental Fe3+ resonance of montmorillonite probably arises from Fe3+ in the octahedral sites and a trans-arrangement of OH groups; however, a large variation in the neighboring environment of these sites exists. In illite this Fe3+ resonance is similar but shows less broadening; it arises from Fe3+ located predominantly in trans-OH octahedral sites, with some Fe3+ being located in cis-OH octahedral sites. Because of the increased iron content less variation exists, compared with montmorillonite, in the neighboring octahedral sites. The Fe3+ resonance is narrower still for the glauconites and represents Fe3+ substituting primarily into cis-OH octahedral sites, similar to that previously reported for nontronite.The tetrahedral Fe3+ content is very low for montmorillonite and increases progressively for illite and glauconite, suggesting that a higher tetrahedral Fe3+ content directs Fe3+ in the octahedral layer into cis-OH sites. In montmorillonite, the Fe2+ is located only in trans-OH sites; in illite Fe2+ is largely in trans-OH sites and only slightly in cis-OH sites; and in glauconite, Fe2+ is located largely in cis-OH sites and only slightly in trans-OH sites. These assignments suggest that for Fe2-, the doublet with the larger quadrupole interaction arises from Fe2+ in trans-OH sites and the doublet with the smaller quadrupole interaction, from Fe2+ in cis-OH sites.

THE NATURE OF SMECTITES IN SOME FINE TEXTURED LACUSTRINE PARENT MATERIALS IN SOUTHERN SASKATCHEWAN

Detailed mineralogy and chemistry of the clay fraction of five glacio-lacustrine deposits and of one Cretaceous marine shale (Ashville) were studied. Fine clay separates (< 0.2 μm) of the five parent materials were predominantly smectite with an average chemical composition:[Formula: see text]X-ray diffraction, dehydration, infrared, and chemical analyses, and the Greene-Kelly test showed that the smectite was an iron rich montmorillonite. Similarities in the crystal structure of the five soil parent material clays suggest that they were likely transported from the same source. Despite the differences in percentage of clay minerals, similarities between chemical composition of the coarse and the fine clays is interpreted as an indication of close diagenetic relationships between the predominant smectite and soil mica. High silicate bound iron may have caused a distortion in the crystal lattice and a slightly favorable weathering condition of smectites. However, presence of high exchangeable and soluble magnesium in the soil complex is likely retarding the smectite alteration. Thus, weathering by elemental substitution may have been restricted to the smectite end member only. Key words: Swelling clay soils, iron montmorillonite, chemical composition of smectites, dehydration of smectites

Mineralogical and chemical properties of smectites in a sediment core from the southeastern Pacific

A sediment core section nearly 80 cm long (50 to 125 cm below the sea bottom) from the southeastern Pacific is largely composed of smectites. X-ray, thermal, infrared, and chemical analyses indicate the smectites to be iron-rich montmorillonite (SiO 2, 50.17%; TiO 2, 0.77%; Al 2O 3, 7.11%; Fe 2O 3, 11.46%; FeO, 0.25%; MnO, 0.09%; MgO, 5.41%; CaO, 0.30%; Na 2O, 2.86%; K 2O, 0.57%; H 2O +, 8.02%; H 2O −, 12.03%; total, 99.04%) and aluminous montmorillonite (SiO 2, 49.39%; TiO 2, 1.18%; Al 2O 3, 14.39%; Fe 2O 3, 4.73%; FeO,—; MnO,—; MgO, 3.61%; CaO, 0.23%; Na 2O, 2.12%; K 2O, 0.34%; H 2O +, 6.86%; H 2O −, 15.20%; total, 98.05%). The iron-rich montmorillonite is rare and similar mineralogically and chemically to that of the northeastern Pacific previously reported by the authors. The aluminous montmorillonite is similar to the common type on land. The hypothesis that the iron-rich montmorillonite could have been formed by the interaction of hydrothermal solutions and seawater is supported by circumstantial evidence, whereas the aluminous montmorillonite was probably altered from volcanic ash transported from some other place.

Origin of Iron-Rich Montmorillonite from the Manganese Nodule Belt of the North Equatorial Pacific

AbstractClay minerals in the upper 50 cm of sediment that surround the Cu- and Ni-rich manganese nodules in the North Equatorial Pacific form two fractions: terrigenous (mostly eolian) illite, chlorite, and kaolinite, and authigenic smectite. Smectite increases with depth in box cores from 26 to 39% and from 53 to 66% in the easternmost and westernmost areas respectively, and with distance seaward from the Americas from 26 to 53% in surface deposits. The change in the amount of smectite relative to other clay minerals is due to dilution by terrigenous debris; smectite probably forms at a uniform rate over much of the North Pacific deep-sea floor. The δO18 value for the smectite is +29.6‰ which suggests that it formed authigenically at a temperature characteristic of the deep-sea floor. The smectite is an Fe-rich montmorillonite that probably forms by the low-temperature chemical combination of Fe hydroxides and silica. Silica is derived from dissolution of biogenic debris, and the Fe hydroxide is from volcanic activity at the East Pacific Rise, 4000 to 5000 km to the east. Al in the authigenic montmorillonite may be derived from the dissolution of large amounts of biogenic silica or from river-derived Al that is adsorbed on Fe-Mn hydroxides in the oceans. The Fe-montmorillonite contains relatively abundant Cu, Zn, and Mn and is of possible economic importance as a source of these and other metals.

Orthopyroxene to talc transformation

Mineralogical transformations that occur during the weathering of rocks are complex processes involving both physical and chemical changes. Although it may be difficult to relate the primary minerals to the secondary phases of the weathering process, there is evidence that certain transformations occur topotaxially. The clinopyroxene, hedenbergite, alters to montronite, an iron-rich montmorillonite mineral, topotaxially; the transformation has been modelled by a crystallographic shear of 1/2[101] on (100) of the pyroxene. This shear mechanism converts the chain silicate into a sheet structure. A similar process may be postulated for several other pyroxene alterations. The commonly observed orthopyroxene to talc transformation has been studied in detail using electron microscopy, electron microprobe, optical microscopy and x-ray diffraction.The process has been studied in an interaction zone that develops between unaltered orthopyroxene and talc layers formed along grain boundaries and within cracks. The growth of the interaction zone occurs by the migration of the interface into the unaltered orthopyroxene-Fig. 1.

The petrology and alteration of tertiary basalts of the coalgate area, Northwest Canterbury

Abstract Basaltic volcanism in the Coalgate area spans a period from lowermost Eocene to Pliocene times. The oldest basalt rocks emplaced are olivine dolerite dykes of probable Paleocene age. The main period of activity commenced in the lower Miocene with hyaloclastic eruptions of olivine-augite basalt with strong alkaline affinities (Burnt Hill Ash and Sand Pit Tuff). Subsequently intrusives, extrusives, and breccias rich in labradorite ,and of high alumina character were emplaced (Bluff Basalt). The youngest igneous rocks in the area are three tholeiitic flows — the Harper Hills Basalt. Alteration of tuffs to iron-rich montmorillonite under freshwater and heavy leaching conditions supports arguments previously advanced for the basaltic nature of the parent material of the Coalgate Bentonite and the processes involved in its montmorillonitisation.

An iron-rich montmorillonite in a sediment core from the northeastern Pacific

A sediment core section nearly 230 cm long (190–420 cm below the sea bottom) from the northeastern Pacific is largely composed of smectite. X-Ray, thermal, i.r. and chemical analyses indicate the smectite to be an iron-rich montmorillonite (SiO 2, 51·66%; TiO 2, 0·58%; Al 2O 3, 8·13%; Fe 2O 3, 14·08%; FeO, 0·51%, MnO, 0·29%; MgO, 4·21%, CaO, 0·15%; Na 2O, 1·21%; K 2O, 0·71%; H 2O +, 6·74%; H 2O−, 10·13%; total 98·40%). The hypothesis that the Fe-smectite could have been formed by the interaction of hydrothermal solutions and seawater is by circumstantial evidence.

Formation of clay from granite and its distribution in relation to climate and topography

Chemical weathering can be approached from three interpretive points of view: distribution of the secondary minerals in landscapes, weathering of primary minerals and geochemistry of ions in solution. On granitic rocks it is posible to define both climatic and topographic sequences of distribution of clays in association with weathering products: gibbsite - kaolinite - hydrous iron oxides - hydrous manganese oxides - iron-rich montmorillonite - calcium carbonate - calcium sulfate - sodium carbonates and silicates. These stages appear as an absolute accumulation formed by filling of intergranular pores. Another sequence can be found not in intergranular pores but in the cracks and along the cleavages of primary minerals from which they are derived by relative accumulation. The order of appearance of these secondary minerals remains the same regardless of the nature of climates and the topographic position. The conditions of equilibrium are not identical in the interior of grains of different primary minerals nor in the pores outside of them and the secondary minerals found in the different situations are also not identical. This is well demonstrated by the chemistry of waters draining slopes. The equilibrium diagrams and balances between cations and silica sometimes result in disagreement, proving that equilibrium conditions are not satisfied between solutions circulating in the pores and clay minerals found inside the primary minerals.

Origin of Metalliferous Sediments from the Pacific Ocean

Sediments from near the basement of a number of Deep Sea Drilling Project (DSDP) sites, from the Bauer Deep, and from the East Pacific Rise have unusually high transition metal-to-aluminum ratios. Similarities in the chemical, isotopic, and mineralogical compositions of these deposits point to a common origin. All the sediments studied have rare-earth-element (REE) patterns strongly resembling the pattern of sea water, implying either that the REE's were coprecipitated with ferromanganese hydroxyoxides (hydroxyoxides denote a mixture of unspecified hydrated oxides and hydroxides), or that they are incorporated in small concentrations of phosphatic fish debris found in all samples. Oxygen isotopic data indicate that the metalliferous sediments are in isotopic equilibrium with sea water and are composed of varying mixtures of two end-member phases with different oxygen isotopic compositions: an iron-manganese hydroxyoxide and an iron-rich montmorillonite. A low-temperature origin for the sediments is supported by mineralogical analyses by x-ray diffraction which show that goethite, iron-rich montmorillonite, and various manganese hydroxyoxides are the dominant phases present. Sr87/Sr86 ratios for the DSDP sediments are indistinguishable from the Sr87/Sr86 ratio in modern sea water. Since these sediments were formed 30 to 90 m.y. ago, when sea water had a lower Sr87/Sr86 value, the strontium in the poorly crystalline hydroxyoxides must be exchanging with interstitial water in open contact with sea water. In contrast, uranium isotopic data indicate that the metalliferous sediments have formed a closed system for this element. The sulfur isotopic compositions suggest that sea-water sulfur dominates these sediments with little or no contribution of magmatic or bacteriologically reduced sulfur. In contrast, ratios of lead isotopes in the metalliferous deposits resemble values for oceanic tholeiite basalt, but are quite different from ratios found in authigenic marine manganese nodules. Thus, lead in the metalliferous sediments appears to be of magmatic origin. The combined mineralogical, isotopic, and chemical data for these sediments suggest that they formed from hydrothermal solutions generated by the interaction of sea water with newly formed basalt crust at mid-ocean ridges. The crystallization of solid phases took place at low temperatures and was strongly influenced by sea water, which was the source for some of the elements found in the sediments.

Origin of clay minerals in a Mid-Atlantic Ridge sediment

The coarse and fine-grained mineral fractions of a Mid-Atlantic Ridge sediment (22°N) have been separated and analyzed for Fe and rare-earth elements (REE). Despite changes in Fe abundance, all the chlorites have REE distributions consistent with a derivation from ridge greenstones. The REE distribution of the fine-grained montmorillonite is similar to that of shales, yet differs markedly from that of a coarse locally derived iron-rich montmorillonite. A continental origin for the fine-grained montmorillonite is implied.

Bentonites of Canterbury

Abstract Deposits of Lower Eocene low-grade swelling bentonite of marine origin are widespread in North Canterbury. Large deposits of non-swelling bentonite, of Miocene age and probably formed by the alteration of glassy basalt ash deposited in a freshwater lake, occur in the Harper Hills, 40 miles west of Christchurch. The essential mineral is an iron-rich montmorillonite containing a minor, interlay er ed, non-expanding component and having about 100meq/100g cation exchange capacity saturated with calcium and magnesium ions. The bentonite can be converted to a high-grade swelling form by treatment with sodium carbonate.

GEOCHEMISTRY OF HORNBLENDE ALTERATION IN PLIOCENE RED BEDS, BAJA CALIFORNIA, MEXICO

Research Article| August 01, 1967 GEOCHEMISTRY OF HORNBLENDE ALTERATION IN PLIOCENE RED BEDS, BAJA CALIFORNIA, MEXICO T. R WALKER; T. R WALKER UNIVERSITY OF COLORADO, BOULDER, COLORADO (WALKER AND HONEA) Search for other works by this author on: GSW Google Scholar P. H RIBBE; P. H RIBBE VIRGINIA POLYTECHNIC INSTITUTE, BLACKSBURG, VIRGINIA (RIBBE) Search for other works by this author on: GSW Google Scholar R. M HONEA R. M HONEA UNIVERSITY OF COLORADO, BOULDER, COLORADO (WALKER AND HONEA) Search for other works by this author on: GSW Google Scholar Author and Article Information T. R WALKER UNIVERSITY OF COLORADO, BOULDER, COLORADO (WALKER AND HONEA) P. H RIBBE VIRGINIA POLYTECHNIC INSTITUTE, BLACKSBURG, VIRGINIA (RIBBE) R. M HONEA UNIVERSITY OF COLORADO, BOULDER, COLORADO (WALKER AND HONEA) Publisher: Geological Society of America Received: 27 Jun 1966 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1967, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1967) 78 (8): 1055–1060. https://doi.org/10.1130/0016-7606(1967)78[1055:GOHAIP]2.0.CO;2 Article history Received: 27 Jun 1966 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation T. R WALKER, P. H RIBBE, R. M HONEA; GEOCHEMISTRY OF HORNBLENDE ALTERATION IN PLIOCENE RED BEDS, BAJA CALIFORNIA, MEXICO. GSA Bulletin 1967;; 78 (8): 1055–1060. doi: https://doi.org/10.1130/0016-7606(1967)78[1055:GOHAIP]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The chemical and mineralogical changes that have taken place during intrastratal alteration of hornblende in Pliocene red beds of Baja California, Mexico, were determined by electron-probe microanalysis and X-ray diffraction studies. The hornblende has altered to iron-rich montmorillonite, and thin sections show that this clay ultimately forms hematite-stained matrix. The alteration involves loss of iron, alkalis, alkaline earths, and probably silica. The authigenic clay shows progressive decrease in iron content outward from the decomposing hornblende, indicating selective removal from the clay by intrastratal leaching. The authigenic clay is therefore an important source of iron for hematite pigment, particularly in the matrix of these red beds. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.