Formation Of Montmorillonite Research Articles

Comparative evaluation of airborne AVIRIS-NG and spaceborne PRISMA hyperspectral data in identification and mapping of altered/weathered minerals in Jahazpur, Rajasthan

The present study addresses a comparative evaluation of airborne AVIRIS-NG and spaceborne PRISMA hyperspectral datasets for mapping hydrothermally altered minerals in Jahazpur town (25°25′23.37″N; 75°06′23.17″E) of Bhilwara district in southeastern Rajasthan. This area is located in Aravalli Craton which host notable base metal mineralization namely Rampura-Agucha, Pur-Banera and Rajpura-Dariba. The hyperspectral datasets were classified using spectral angle mapper which identified talc, soapstone, and kaolinite clay minerals in the study area. The samples were collected from the identified areas. Their spectral signature was compared with AVIRIS-NG, PRISMA, and USGS mineral spectral library and showed greater similarity in spectral absorption features. Conventional geological techniques such as thin section studies and XRD diffraction pattern analysis were carried out to validate the presence of minerals in the study area. Comparative analysis shows AVIRIS-NG and PRISMA sensor capability to identify altered/weathered minerals. The PRISMA dataset did not identify small surface exposure of talc deposit at the Padampura location due to its low spatial resolution (30 m) and SNR values. In contrast, AVIRIS-NG imagery successfully maps this exposure in the classified mineral map. The types of alteration in the area show formation of talc mineral from dolomite and argillic alteration resulting in kaolinite and montmorillonite formation. Therefore, airborne AVIRIS-NG proves its efficiency in mapping of relatively small surface exposure of altered minerals compared with the spaceborne PRISMA hyperspectral dataset.

Rare earth nanominerals in bentonite deposits of the Eocene Texas coastal plains

Mineral phases and modes of occurrence of rare earth elements and yttrium (REE) in weathering environments are poorly understood but constitute a potential economic source. In Texas, deposits of bentonite that formed by alteration of rhyolitic ash in a coastal and marine influenced environment show REE enrichment comparable to some North American coal and deposits that are under consideration for extraction. We investigated the post depositional mineralization and modes of REE occurrence in a bentonite deposit from Gonzales, Texas, in which total REE concentration exceeds 450 ppm.Scanning electron microscopy (SEM) revealed the presence of sub-micron to nano-size REE phosphate particles dispersed in the montmorillonite matrix, aggregated at the edge of incompletely altered phenocrysts, or in the void space separating montmorillonite stacks. Chemical composition distinguishes a prevalent group of phosphate with Ce > La ~ Nd > Y > Pr > Sm, also bearing Ca and trace amounts of Th and U, and a less common Y-phosphate with trace amounts of other REEs. Transmission electron microscopy (TEM) analysis indicated that the most common particles exhibit a platy morphology, with a diameter smaller than 200 nm and a thickness of less than 100 nm. Electron diffraction, 3D electron diffraction, and high-resolution TEM clearly showed that the mineral phase was monazite. We interpreted the observed REE geochemistry and mineralogy as dissolution of volcanic glass deposited in an alkaline aqueous environment that released REEs into pore water that became oversaturated due to precipitation of montmorillonite, the availability of P in the solution prompted precipitation of monazite nanoparticles. The reduction in permeability following formation of montmorillonite and precipitation of opal in void spaces facilitated accumulation.

PH dependent leaching characterization of major and trace elements from fly ash and metakaolin geopolymers

The leaching characteristics of Cl−, SO42−, Na, K, Al, Si, Ca, Mg, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Sr, Tl, V, Zn from fly ash and metakaolin geopolymer mortars were characterized in a broad pH range (1–14) in this work. Apart from revealing the partitioning of chemical species between the solid and aqueous phase, the acid neutralization property of both geopolymers were studied. In contrast with the virtually pH independent characteristic of chloride and sulfate, the leaching of the other elements showed pH dependent features, which can be further divided into amphoteric, cationic and oxyanionic patterns. Formation of montmorillonite and amorphous silica were detected by X-ray diffraction after the leaching. The leaching results and mineralogical measurement were coupled with geochemical modelling to identify the solubility controlling phases of Al, Si, Ca and Mg.

Low-Temperature Hydrothermal Alteration of Trachybasalt at Conical Seamount, Papua New Guinea: Formation of Smectite and Metastable Precursor Phases

AbstractThe conversion of volcanic glass to secondary alteration products is one of the most common mineralogical transformations during low-temperature hydrothermal alteration of submarine basalts. To better understand the mechanism and kinetics of this transformation, porphyritic and formerly glassy trachybasalt, recovered from Conical Seamount, Papua New Guinea, was studied in detail. Low-temperature interaction of trachybasalt with hydrothermal fluids at this submerged volcano occurred in response to the formation of submarine epithermal-style gold mineralization. Alteration of the coherent volcanic rocks is heterogeneous with pronounced differences in alteration intensity occurring between igneous minerals and the surrounding glassy groundmass. In comparison to the volcanic glass, the crystalline phases were less prone to hydrothermal alteration with the alteration susceptibility decreasing from clinopyroxene through biotite to feldspar. Low-temperature alteration of clinopyroxene resulted in the formation of abundant saponite-like smectite with no topotactic relationship being observed between the two phases. In contrast, the conversion of biotite to smectite involved structural inheritance as the orientation of common structural blocks was maintained during alteration. Transmission and analytical electron microscopy revealed that pervasive alteration of interstitial glass in the groundmass of the trachybasalt resulted in the formation of montmorillonite- and saponite-like smectite whereby smectite composition is strongly influenced by the glass chemistry. The occurrence of poorly crystalline domains with a 0.3 to 0.4 nm layer spacing in the altered interstitial glass suggests that the transformation of glass to smectite involved the formation of a transitional alteration product. Comparison with the results of previous studies highlights the fact that the glass-to-smectite transformation can proceed through more than one reaction pathway. Reaction style and reaction progress are controlled by kinetic factors such as the mode of fluid transport triggering alteration in the low-temperature hydrothermal environment. Alteration of the trachybasalt at Conical Seamount is inferred to have taken place at a comparably low fluid-rock ratio as the low permeability and the absence of primary fractures and joints restricted fluid circulation through the coherent volcanic rocks.

The mobility of uranium and other elements during alteration of rhyolite ash to montmorillonite: A case study in the Troublesome Formation, Colorado, U.S.A.

An unusual occurrence of juxtaposed glassy and clay-altered ash was sampled to estimate the degree and type of element mobility during alteration of glass to montmorillonite. The results are particularly interesting in that major mobilization of uranium is indicated. Closely spaced samples of glassy and montmorillonitic ash were collected from the same 20–50 cm thick stratigraphic horizon in the Troublesome Formation (Miocene) of northwestern Colorado. Sharp contacts exist between glassy ash and underlying pink montmorillonite and indicate that water-saturated conditions were restricted to basal ash layers. Formation of montmorillonite instead of zeolites suggests that the water was not highly saline or alkaline. Isotopic and chemical analyses of glassy and clay-altered samples indicate the following: 1. (1) Montmorillonite has U concentrations which are only 10–15% of the concentrations in coexisting glass. Similarly depleted elements include Cs, Rb, Na and K. Much smaller depletions of these elements in some glassy samples serve as sensitive indicators of incipient alteration of glass to montmorillonite. 2. (2) Abundances of relatively insoluble elements such as Th, Ta, Hf and Al are slightly higher (5–50%) in clay-altered ash and serve as indicators of the maximum levels of enrichment in residual material. Greater enrichment of elements such as Ca, Mg, Sr, Sc, P, Cr and Co indicate structural incorporation, adsorption, or ion-exchange uptake by clay or secondary hydrous oxides of Fe and Mn. 3. (3) The rare-earth-element patterns and abundances in glass are sufficiently mimicked by detritus-free montmorillonite to document the compositional equivalency of the two. 4. (4) Radioactive equilibrium exists between 238U and its decay products 234U and 230Th. This documents minimal open-system mobility of U within the last ∼ 0.3 Ma.

CARACTERISTIQUES MINERALOGIQUES ET CHIMIQUES DE QUELQUES SOLS SABLEUX DU QUEBEC EN REGARD DE LEUR EVOLUTION PEDOLOGIQUE

A, B and C horizons of 13 sandy soil series were sampled in the lowlands of southern Quebec. From the amounts of pyrophosphate-extractable Fe and Al and clay contents, nine of these profiles were classified as Podzolic soils while the others were Brunisols. Formation of montmorillonite and dissolution of chlorite in Ae horizons indicate intense weathering of the minerals at this level. In the B horizons, vermiculite that was present in the parent material or resulted from the alteration of illite was often chloritized. Values of pH measured in 1 M NaF were generally higher than 10.2 for the B horizons. The amounts of phosphorus retained by the samples varied in the following ranges: 23–397 μg P/g of soil for A horizons, 301–1578 μg P/g of soil for B horizons and 71–296 μg P/g of soil for C horizons. Cation exchange capacity of the soils was lower than 10 meq/100 g of soil, except in those horizons that contained high amounts of organic matter and where values up to 27.6 meq/100 g were measured. Using regression equations, values were obtained for the CEC of the organic matter and the clay fraction of these sandy soils.

Mobility of Uraniun and Other Elements During Alteration of Air-Fall Ash to Montmorillonite: Case Study: ABSTRACT

An unusual occurrence of juxtaposed glassy and clay-altered ash was sampled to determine the extent of element mobility during glass diagenesis. The results are particularly interesting in that major mobilization of uranium is indicated. Closely spaced samples of glassy and clay-altered ash were collected from the same 20 to 50-cm-thick stratum in the Troublesome Formation (Miocene) of northwestern Colorado. Sharp contacts present between glassy ash and underlying pink montmorillonite may indicate water-saturated conditions restricted to basal ash layers or deposition in a body of water that dried up during the course of the eruption. Formation of montmorillonite instead of zeolites indicates that the water was not highly alkaline or saline. Multielement analysis of glass and clay-altered samples indicates three things. (1) Montmorillonite has 85 to 90% less uranium than the coexisting glass; similarly depleted elements include Cs, Rb, Na, and K; much smaller depletions of these elements in some glassy samples serve as particularly sensitive indicators of incipient alteration of this type. (2) The abundances of relatively insoluble elements such as Th or Ta are slightly higher (5 to 40%) in clay-altered ash and serve as indicators of the maximum levels of element enrichment in residual material; greater enrichment of elements such as Sc, Sr, and Co indicate adsorptive uptake by clay or by secondary oxides of iron and manganese. (3) The rare earth element (REE) patterns and abundances in glass are sufficiently mimicked by detritus-free montmorillonite to ocument the original compositional equivalency of the two. End_of_Article - Last_Page 574------------

規則混合層鉱物の水熱合成

The hydrothermal formation of regularly interstratified mica-montmorillonite and chlorite-montmorillonite was discussed with the following subject; (1) formation of montmorillonite as a preceding phase of regularly interstratified minerals, (2) change from irregular interstratfication to regular one, and (3) influences of kinds of interlayered cations on the formations of interstratified minerals.

Alteration of sandstone intercalation in the Upper Nanakura tuff member occurring at Futatsui district, Yamamot-gun, Akita prefecture, Japan.

The Upper Nanakura tuff member is widely distributed at Futatsui area. This members mainly composed of vitric tuff and altered to clinoptilolite except of the sandstone intercalation. The sandstone is 1-2m thick and contains mainly montmorillonite. Chemicaly this sandstone is abundant in MgO and CaO, and tuff which contains clinoptilolite is abundant in Na2O and K2O. From the laboratory experimental data montmorillonite is easily formed under Mg environment. So the formation of montmorillonite in sandstone intercalation of vitric tuff is supposed to be depended on some affection of Mg rich solution after origination of clinoptilolite by the low grade metamorphism. The solution passed easily through the sandstone intercalation because of better porosity and permeability than tuff, so Mg addition was occurred only in sandstone.

ETUDE COMPARATIVE DE SOLS DES LAURENTIDES, QUEBEC

Five profiles were sampled in the till deposits of the Laurentides Hills. Two were obtained at Duchesnay, near Quebec City and three north of Montreal, including two profiles of the Gatineau and one of the Sainte-Agathe series of soils. Results of the particle-size distribution, morphological and mineralogical analyses suggested that the parent material was similar in all profiles. A high bulk density, about 2.00 g/cm3, was observed in the fragic horizon. Maximum weathering was found in the A horizons resulting in the formation of montmorillonite and kaolinite. The X-ray diffraction patterns obtained for the samples from Duchesnay were better defined than those obtained from the other profiles. In addition to illite, chlorite and vermiculite, two types of interstratified minerals were observed: illite–montmorillonite in the Podzolic-B and illite–vermiculite in the fragic horizons. High values, up to about 700 meq/100 g were obtained for the Al interlayers in the clay fraction. These profiles were classified as fragic ferro-humic Podzols (Sainte-Agathe and the profiles from Duchesnay) and fragic humo-ferric Podzols (Gatineau). The concept of fragic horizon in the soils from the Laurentides is discussed.

Evaluation of clay mineral equilibria in some clay soils (usterts) of the brigalow lands

A model of the thermodynamic stability of the montmorillonite-kaolinitequartz system is constructed on the basis of published values of standard free energies of formation. The effect of differences in stability of montrnorillonite is estimated by considering different montmorillonites. Compositions of soil solutions from soil samples from the brigalow lands of south-east Queensland with a montmorillonite-kaolinite-quartz mineralology are plotted against equations for the montmorillonite-kaolinite, montmorillonite-quartz, and montmorillonite-kaolinite-quartz equilibria. The effect of different assumptions regarding the relation between the composition of saturation extracts and soil solutions is shown. A shallow surface zone is established with a chemical environment favourable to the formation of montmorillonite. In the deeper layers the soil solution is much closer to equilibrium with the mineral constituents, or quartz may be favoured instead of montmorillonite. Kaolinite cannot form in the present chemical environment. The high kaolinite content, therefore, is suggested to be a relict from an earlier phase of soil formation. It is further suggested that the strong gilgai, and the acidity of the deeper soil layers, may be explained by the hypothesis that montmorillonite has formed in originally kaolinitic materials, because the kaolinite to montmorillonite conversion is accompanied by volume increase, and release of H+ ions.

Iron‐Rich Montmorillonite Formation in Soils Derived from Serpentinite

AbstractMontmorillonite, identified by X‐ray diffraction, is the predominant clay mineral in the B horizons of four widely separated California soils (Henneke, Dubakella, and Fancher series and one from the New Idria area) derived from serpentinite. The < 0.2µ fractions contain respectively, 81, 68, 71, and 33% montmorillonite as determined by CEC determination. These fractions contain 57.5, 54.9, 62.5, and 50.0% SiO2; 17.2, 18.4, 17.6, and 7.5% combined Fe2O3 (by chemical analysis after removal of free Fe2O3); 7.2, 4.3, 8.7, and 25.0% MgO; and 4.3, 10.4, 1.0, and 6.1% Al2O3. Much of the MgO can be attributed to < 0.2µ serpentine minerals, identified by electron microscopy. The montmorillonite has a high content of Fe in octahedral position, represented by the range in octahedral sheet formula, Fe1.8–2.7Al0.2–1.8Mg0–1.1, calculated for the four soil clays. Mg is the predominant exchangeable cation in the < 2 mm soil (67–96% of the total exchangeable cations). The parent serpentinite contrasts with the soil clays in having lower SiO2 (43.3, 38.1, 40.0, and 39.8%) and Fe2O3 (6.6, 3.6, 8.9, and 3.1%, after magnetite removal from the parent rock samples), higher MgO (33.7, 41.0, 42.2, and 40.3%), and lower Al2O3 (0.4, 2.4, 1.5 and 0.7%). Leaching of serpentinite removed much of the Mg; concurrently Si, Fe, and Al were enriched in the pedogenic montmorillonite which formed.

Determination of Silica in Citrate‐Bicarbonate‐Dithionite Extracts of Soils

AbstractA procedure was developed for the determination of Si directly in citrate‐dithionite extracts of soils. The procedure, which provides for noninterference by citrate, dithionite, Fe, and P was developed for measurement of the absorbance of the reduced β‐molybdosilicic acid in the working range of 5 to 25 µg of Si in 50 ml. Interference by unoxidized dithionite was eliminated by bubbling air through the extract. The interference by citrate was prevented by an excess of molybdate; that by Fe and P by tartaric acid addition.The citrate‐dithionite treatment released, per gram of soil, 3 to 174 mg of Fe2O3, 0.8 to 42 mg of Al2O3, and 0.1 to 3.8 mg Si(OH)4. The water‐soluble silica ranged from 0 to 26 µg of Si(OH)4 per ml of solution before removal of reductantsoluble Fe2O3 and Al2O3; it increased into the range of 5 to 58 after removal. At any given pH of Henry soil (in the pH range of 4 to 7), the water‐soluble silica increased markedly as a result of previous citrate‐bicarbonate‐dithionite extraction. The release of Fe, Al, and Si that occurred with the various soils on reduction indicates a possible mechanism by which these constituents may increase sufficiently to support the well‐known formation of montmorillonite from soluble and alluviated materials moved into positions of slow drainage. These constituents in solution would also favor preservation of any montmorillonite present in soil parent materials.

Petrogenesis of Bentonites

AbstractThe formation of typical bentonites occurs in two stages. The first stage comprises the development, transportation, and deposition of the volcanic ash, which determines the geometry and structure of the bentonite rock and influences the alteration of the ash during the second stage. The second stage encompasses the alteration of volcanic glass to montmorillonite and other minerals.The distribution of ash particles in the bentonite beds of Wyoming is satisfactorily explained by a theoretical model based on equations similar to heat flow equations. An extended model, assuming a disk-shaped volcanic cloud containing ash particles, also accounts for the geometrical shapes and geographic variations of the textural parameters of the bentonite beds.The alteration of Wyoming bentonite ashes to montmorillonite occurred undoubtedly at low temperatures in an aqueous environment. Petrologic evidence indicates that all of the Wyoming ashes and many ashes deposited elsewhere contained sufficient magnesium to form montmorillonite with no addition necessary from without. Also evidence indicates variations of pH of perhaps 5 to 8 made little difference in the alteration products of the ashes.Laboratory evidence of the processes and products of alteration of ashes to bentonite accord with field observation. With simplifying assumptions, the formation of montmorillonite from volcanic glass may be elucidated from the viewpoint of the stability of montmorillonite with respect to other similar minerals. The results of theoretical calculations of the mineral stabilities will be presented. Three energy parameters will be considered: the Coulomb energy, Van der Waals’ repulsion, and the London energy Thermal motion of the atoms will be taken into account.