University of Illinois Urbana-Champaign

Experimental Determination of Smectite Hydration States Under Simulated Diagenetic Conditions (high-Temperature, X-Ray Diffraction, Dehydration)

Colten, Virginia Ann

This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.

Permalink

https://hdl.handle.net/2142/71138

Description

Title
Experimental Determination of Smectite Hydration States Under Simulated Diagenetic Conditions (high-Temperature, X-Ray Diffraction, Dehydration)
Author(s)
Colten, Virginia Ann
Issue Date
1985
Department of Study
Geology
Discipline
Geology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Geochemistry
Abstract
  • The hydration states of a dioctahedral smectite in contact with saline solutions were determined at temperatures and hydraulic pressures that simulate burial diagenetic environments. A high-pressure high-temperature X-ray cell, mounted on an automated General Electric XRD3 X-ray diffractometer, was used to monitor the basal reflections.
  • Sodium-saturated Cheto montmorillonite exists as a two water layer complex, with basal spacing between 15.2 and 15.7 (ANGSTROM) in 1 and 5 molal NaCl brines at hydraulic pressures to 6700 psi and temperatures to 200(DEGREES)C. No change in hydration state was detected although thermodynamic analysis predicts that loss of interlayer water may occur at temperatures above 63 and 135(DEGREES)C for the 5 and 1 molal NaCl systems, respectively.
  • Na-Cheto exists as a three water layer complex, d(001) = 18.4-18.9 (ANGSTROM), in 0.5 molal NaCl, at pressures to 750 psi and temperatures less than 100(DEGREES)C. Reversible loss of the third water layer occurs between 100 and 175(DEGREES)C. Thermodynamic estimates of the range of temperatures over which the third water layer might be expelled are in good agreement with the experimental results.
  • Cheto montmorillonite exhibits irreversible collapse of 30% of the 12.4 (ANGSTROM) layers upon K-saturation at room temperature and pressure. Experimental X-ray diffraction analyses showed that a mixed-layered clay is present. However, low intensities and lack of the first order reflection preclude further interpretation of the results.
  • The results of this investigation affirm the generally accepted inverse relationship between salinity and swelling. They also demonstrate the inhibiting effect of high layer charge. Within the range of pressures ((LESSTHEQ) 6700 psi), temperatures ((LESSTHEQ) 200(DEGREES)C), and salinities ((GREATERTHEQ) 1 m NaCl) common to areas where illitization of smectite is known to occur, Na-smectite is stable as a two water layer complex. This negates the previously proposed mechanism for stepwise loss of interlayer water at depth. The results of this investigation provide further evidence for the loss of the interlayer water during the illitization reaction, which requires layer charge build-up and fixation of K('+) as the interlayer cation.
Graduation Semester
1985
Type of Resource
text
Permalink
http://hdl.handle.net/2142/71138

Owning Collections

Graduate Dissertations and Theses at Illinois PRIMARY
Graduate Theses and Dissertations at Illinois
Dissertations and Theses - Geology