Alkalinity and Formation of Zeolites in Saline Alkaline Lakes

Mariner, R.H.; Surdam, Ronald C.

doi:10.1126/science.170.3961.977

Cited by 121 publications

(73 citation statements)

References 10 publications

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“…Leaching of alkalis and a high Mg activity promote the formation of smectite (Hay, 1977;Senkayi et al, 1984). When leaching is not effective, zeolites crystallize, usually from precursor gels (Mariner and Surdam, 1970;Steefel and van Cappellen, 1990). Smectite generally forms in the initial stages of the alteration, where the (Na + + K+)/H + activity ratio of the fluid phase is low (Sheppard and Gude, 1973;Hay and Guldman, 1987).…”

Section: Introductionmentioning

confidence: 99%

Formation and Growth of Smectites In Bentonites: A Case Study From Kimolos Island, Aegean, Greece

Christidis

2001

Clays and clay miner.

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Abstract--The low-temperature alteration of a rhyolitic rock from Kimolos Island, Aegean, Greece, yielded an alteration profile characterized by gradual transition from fresh glass to bentonite containing homogeneous Chambers-type montmorillonite and then to a mordenite-bearing bentonite. Both mordenite and smectite were formed from poorly crystalline precursors, which probably had compositions comparable to that of the crystalline end-product. However, their composition may have been modified to some degree after reaction with the fluid phase. Particle length and width measurements of smectite crystals yielded lognormal profiles, which suggest supply-controlled crystal growth in an open system or random ripening in a closed system. The former mechanism is in accordance with the observed sustained supply of Mg and Fe by the fluid phase throughout the alteration profile and is believed to be the dominant formation mechanism of smectites in bentonites in general. In the mordenite-bearing zone, random ripening is expected in domains with low permeability, in which the system was essentially closed, favoring the formation of mordenite. The level of supersaturation with respect to smectite was probably lower in the mordenite-bearing zone. Smectite probably affected pore-fluid chemistry either through ion exchange or via dissolution of initially formed K-bearing smectite. The latter process raised the K+/(Na + + Ca 2+) activity ratio of the pore-fluid favoring K-bearing mordenite.

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Section: Introductionmentioning

confidence: 99%

Formation and Growth of Smectites In Bentonites: A Case Study From Kimolos Island, Aegean, Greece

Christidis

2001

Clays and clay miner.

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“…Kinetic effects (e.g., low temperatures, short alteration times) influence the formation of poorly crystalline phases such as hydrotalcite (Abdelouas et al, 1994) and allophane Tomita, 1992, 1995;Kawano et al, 1993). Low pH promotes the formation of halloysite and kaolinite (Nagasawa, 1978;Kawano and Tomita, 1995), neutral and slightly basic conditions favor smectite formation Ghiara et al, 1993;, and basic pH values promote zeolite formation (Mariner and Surdam, 1970;Hall, 1998). Na availability may be a factor, with higher Na concentrations in solution favoring smectite over zeolite (Keene et al, 1976;Tomita et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Electron Microscopy Study of Volcanic Tuff Alteration to Illite-Smectite Under Hydrothermal Conditions

Fuente

Cuadros

Fiore³

et al. 2000

Clays and clay miner.

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Abstract--Experimental alteration of volcanic tuff from Almeria, southeastern Spain, was performed in solutions with different Na/K ratios (0.01, 1, 10, and 100), different total salt concentrations (0.01, 0.1, 0.2, 0.33, and 1 M), and in deionized water, at 60, 80, 120, and 160~ for periods of 60, 90, 180, and 360 d. Two particle size fractions of volcanic tuff were used: 10-200 and 20-60 p,m. Alteration products were examined by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), laser-particle size analysis, scanning electron microscopy equipped with an energy dispersive X-ray spectrometer (SEM-EDS), image computer analysis, and transmission electron microscopy with microanalysis (TEM-AEM). XRD detected neoformed phases only in the products from experiments of 180-360 d at high temperatures (120-160~and with Na/K ratios above unity and in deionized water. The synthesized phase is a random mixed-layer illite-smectite (I-S) with 75% smectite. The quantity of newly formed I-S, determined by FTIR, ranged between 3-30%. There was no apparent change in grain size and shape of the grains after the experiments as compared to before.SEM-EDS and TEM-AEM revealed the following alteration sequence: 1) intense etching on glassgrain surfaces; 2) formation of hemispherical morphologies on grain surfaces; 3) precipitation of very thin, individual flakes of illite-smectite on glass-grain surfaces; 4) development of I-S at the edges of glass grains; and 5) development of I-S honeycomb structures either covering large areas of the glass grains or resulting from the complete alteration of glass grains. A direct transformation of glass to I-S seems to be the major reaction mechanism, although there also is evidence of glass dissolution and subsequent I-S precipitation.

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“…The high alkalinity is caused by bicarbonate concentration by way of sulfate reduction process. Mariner and Surdam (1970) noted that the activity of silica was high in alkali solutions, but the activity of alumina increased more rapidly with increase in alkalinity. The Si/Al ratio is the controlling factor for the zeolite formation and the concentration of alumina would be favored in the Hole 400A environment.…”

Section: Origin Of Clinoptilolite and Opal-ctmentioning

confidence: 99%

Transformation of Opaline Silica in Sediments from Bay of Biscay and Rockall Bank

Kagami¹

1979

Initial Reports of the Deep Sea Drilling Project

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X-ray powder diffraction analyses of sponge spicules and radiolarians taken from cores drilled at the Bay of Biscay and Rockall Bank in the northeast Atlantic show marked changes in silica minerals. In Hole 400A, opal-A exists in the Miocene-Oligocene sequence, opal-A coexists with clinoptilolite which shows pseudomorph from biogenous shells in the Eocene-Paleocene sequence, and opal-CT coexists with the clinoptilolite in the Albian sequence. Formation of the clinoptilolite may be controlled by concentration of aluminum and alkali ions which is supported by silicate reactions observed in the interstitial water of the site.The mode of occurrence indicates that opal-CT alone occurs when calcium carbonate in sediments is over 80 per cent. The marked depletion of alkalinity in Site 406 and the scarcity of aluminum and metallic cations in interstitial solutions seems to favor precipitation of opal-CT.The origin of the bedded cherts in the Miocene-Oligocene and Eocene sequences at Hole 400A may be explained by the sedimentary processes such as turbidity currents and winnowing currents, for example, contour currents. A nodular type porcelanite at Site 406 may be formed by the deposition of silica as colloidal state which have been dissolved from the nearby diatomite layer.

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Alkalinity and Formation of Zeolites in Saline Alkaline Lakes

Cited by 121 publications

References 10 publications

Formation and Growth of Smectites In Bentonites: A Case Study From Kimolos Island, Aegean, Greece

Formation and Growth of Smectites In Bentonites: A Case Study From Kimolos Island, Aegean, Greece

Electron Microscopy Study of Volcanic Tuff Alteration to Illite-Smectite Under Hydrothermal Conditions

Transformation of Opaline Silica in Sediments from Bay of Biscay and Rockall Bank

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