Dioctahedral smectite reactions at elevated temperatures: Effects of K-availability, Na/K ratio and ionic strength
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Abstract
Hydrothermal experiments were conducted to measure the effects of K availability, Na/K ratio and ionic strength in chloride solutions on the rate and extent of the reaction of smectite to interstratified illite/smectite. The < 2 μm fraction of a bentonite was treated hydrothermally at temperatures of 200, 250, 300, 350, 400 and 450°C for run times of up to 30 days in the presence of 0.33, 0.66 and 1.00 equivalents of K per O10(OH)2. The effect of K-content on reaction progress is dramatic at low (0.33 eq.) K concentrations, but diminishes above a concentration of 0.66 equivalents. The effect of K-content is also more important at lower temperatures than at higher temperatures. Addition of K above that required to satisfy the cation exchange capacity of the smectite reduced the amount of chlorite byproduct and produced authigenic K-feldspar at the highest K-concentration.
Similar experiments were run using Na/K equivalent ratios of 0 to 25 and total solution molalities of 0 to 3.75 molal. Because these experiments were small fixed-volume experiments, it was necessary to vary two of the three key variables (K-content, Na/K ratio, ionic strength simultaneously. The data suggest, however, that K-content has a much stronger effect than either Na/K ratio or ionic strength on illitization reaction progress.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Dioctahedral smectite reactions at elevated temperatures: Effects of K-availability, Na/K ratio and ionic strength |
| Series title | Applied Clay Science |
| DOI | 10.1016/0169-1317(92)90032-I |
| Volume | 7 |
| Issue | 1-3 |
| Year Published | 1992 |
| Language | English |
| Publisher | Elsevier |
| Description | 16 p. |
| First page | 97 |
| Last page | 112 |
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