Modeling the dissolution behavior of standard clays in seawater

Journal Article · Sat Oct 31 23:00:00 EST 1987 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(87)90369-3· OSTI ID:5255271

Mackin, J E; Swider, K T ^[1]

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1. State Univ. of New York, Stony Brook (USA)

The present investigation tests a model to explain the behavior of dissolved Si during early diagenesis in sediments. The model assumes that low-Fe clays and other minerals can be treated simply as Al hydroxides, having attached silica. When the minerals are placed in seawater solutions, Si is released, causing exposure of fresh Al-octahedra, which are reactive toward Si and other elements in solution. Standard clays (kaolinite, montmorillonite) and solid silicic acid were suspended in seawater solutions in various combinations, and dissolved Al, Si, Ca, pH and alkalinity were determined as a function of time. The theoretical model correctly predicts the behavior of Si in mixtures of the different minerals, based upon the dissolution behavior of the minerals in suspension alone. Further, the decrease in the alkalinity of kaolinite-containing seawater solutions, where carbonate dissolution, organic matter decomposition and reduced sulfur oxidation are apparently unimportant, can be predicted from a simple extrapolation of the silica model results. The alkalinity changes observed in this study, as well as the pH changes observed in standard clay suspensions by other researchers, can be explained simply by equilibration of the charge on exposed Al-octahedra with the pH of the surrounding waters. The results of this study indicate that theoretical models of Si diagenesis in sediments should have general usefulness for predicting the effects of clay dissolution on sediment properties.

• OSTI ID: 5255271
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 51:11; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ACID NEUTRALIZING CAPACITY
ALUMINIUM COMPOUNDS
ALUMINIUM HYDROXIDES
ALUMINIUM SILICATES
CARBONATE MINERALS
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
CHEMISTRY
DIAGENESIS
DISSOLUTION
GEOCHEMISTRY
GEOLOGIC MODELS
HYDROGEN COMPOUNDS
HYDROXIDES
KAOLINITE
KINETICS
MATHEMATICAL MODELS
MINERALOGY
MINERALS
MOLECULAR MODELS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
REACTION KINETICS
SEAWATER
SEDIMENTS
SILICA
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
SOLVENT PROPERTIES
STRUCTURAL CHEMICAL ANALYSIS
WATER
WATER CHEMISTRY