Advertisement

Clays and Clay Minerals

, Volume 40, Issue 5, pp 547–554 | Cite as

Diagenetic Illite-Chlorite Assemblages in Arenites. II. Thermodynamic Relations

  • P. Aagaard
  • J. S. Jahren
Article

Abstract

The internal equilibrium status among chlorite-illite pairs has been evaluated through coupled substitution reactions. Compositional data of chlorites and illites from arenites at present burial temperatures between 90° and 180°C have been used to calculate end member activities and reaction quotients of the combined Tschermak reaction:
$$Muscovite\;+\;Clinochlore\;=\;MgAl-celadonite\;+\;Amesite.$$

The reaction quotient data in the 90° to 180°C temperature range have then been compared with the equilibrium curve for the same reaction, and found to be in reasonable agreement. This indicates that chlorites and illites in these arenites grow at near equilibrium conditions.

The data set has also been compared with chlorite-illite pairs from hydrothermally altered arenites of the Salton Sea area. For chlorite-illite containing assemblages, these data agree well with the diagenetic ones. The introduction of biotite at higher temperatures alters with the iron-magnesium distribution and breaks down the substitution relationship between chlorite and illite.

The model predicts an increasing stability of muscovite and clinochlore components with increasing temperature, while celadonite and amesite would be stabilized with increasing pressure. This is consistent with high pressure occurrences of phengite. However, at the low pressure region of diagenesis and hydrothermal alteration, the temperature effect is dominant.

Key Words

Arenites Diagenesis Illite/Chlorite Tschermak reaction 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Aagaard, P., and Helgeson, H. C. (1983) Activity/composition relations among silicates and aqueous solutions: II. Chemical and thermodynamic consequences of ideal mixing of atoms on homological sites in montmorillonites, illites, and mixed-layer clays: Clays & Clay Minerals 51, 207–217.CrossRefGoogle Scholar
  2. Aagaard, P., Egeberg, P. K., and Jahren, J. S. (1992) North Sea clastic diagenesis and formation water constraints: in Water-Rock Interaction, Y. K. Kharaka and A. S. Maest, eds., Balkema, Rotterdam, 2, 1147–1152.Google Scholar
  3. Bishop, B. P., and Bird, D. K. (1987) Variation in sericite compositions from fracture zones within the Coso Hot Springs geothermal system: Geochim. Cosmochim. Acta 51, 1245–1256.CrossRefGoogle Scholar
  4. Cathelineau, M. (1988) Cation site occupancy in chlorites and illites as a function of temperature: Clay Miner. 23, 471–485.CrossRefGoogle Scholar
  5. Cathelineau, M., and Izquirdo, G. (1988) Temperature-composition relationships of authigenic micaceous minerals in the Los Azufres geothermal system: Contrib. Mineral. Petr. 100, 418–428.CrossRefGoogle Scholar
  6. Cathelineau, M., and Neiva, D. (1985) A chlorite solid solution geothermometer. The Los Azufres (Mexico) geothermal system: Contrib. Mineral. Petr. 91, 235–244.CrossRefGoogle Scholar
  7. Curtis, C. D., Hughes, C. R., Whiteman, J. A., and Whittle, C. K. (1985) Compositional variations within some sedimentary chlorites and some comments on their origin: Mineral. Mag. 49, 375–386.CrossRefGoogle Scholar
  8. Egeberg, P. K., and Aagaard, P. (1992) Formation water chemistry in relation to the stability of detrital and authigenic minerals in clastic reservoirs from offshore Norway: Marine Petr. Geol. (in press).Google Scholar
  9. Fawcett, J. J., and Yoder Jr., H. S. (1966) Phase relations of chlorites in the system MgO-Al2O3-SiO2-H2O: Amer. Mineral. 51, 353–380.Google Scholar
  10. Guidotti, C. V. (1984) Micas in metamorphic rocks: in Micas, Reviews in Mineralogy, S. W. Bailey, ed., Mineralogical Society of America, Washington, D. C., 13, 357–467.Google Scholar
  11. Helgeson, H. C., and Aagaard, P. (1985) Activity/composition relations among silicates and aqueous solutions. I. Thermodynamics of intrasite mixing and substitutional order/disorder in minerals: Amer. J. Sci. 285, 769–844.CrossRefGoogle Scholar
  12. Helgeson, H. C., Delany, J. M., Nesbitt, H. W., and Bird, D. K. (1978) Summary and critique of the thermodynamic properties of rock forming minerals: Amer. J. Sci. 267, 729–804.CrossRefGoogle Scholar
  13. Hillier, S., and Velde, B. (1991) Octahedral occupancy and the chemical composition of diagenetic (low-temperature) chlorites: Clay Miner. 26, 149–168.CrossRefGoogle Scholar
  14. Jahren, J. S. (1991) Evidence of Ostwald ripening related recrystallization of chlorites from reservoir rocks offshore Norway: Clay Miner. 26, 169–178.CrossRefGoogle Scholar
  15. Jahren, J. S., and Aagaard, P. (1989) Compositional variations in diagenetic chlorites and illites, and relationships with formation-water chemistry: Clay Miner. 24, 157–170.CrossRefGoogle Scholar
  16. Jahren, J. S., and Aagaard, P. (1992) Diagenetic illite-chlorite assemblages in arenites. I. Chemical evolution: Clays & Clay Minerals, this issue.Google Scholar
  17. Jenkins, D. M., and Chernosky, J. V. (1986) Phase equilibria and crystallo-chemical properties of Mg-chlorite: Amer. Mineral. 71, 924–936.Google Scholar
  18. Johnson, J. W., Oelkers, E. H., and Helgeson, H. C. (1992) SUPCRT92: A Software Package for Calculating the Standard Molal Thermodynamic Properties of Minerals, Gases, Aqueous Species, and Reactions from 1 to 5000 bars and 0° to 1000°C: Computers and Geosciences (submitted).Google Scholar
  19. Kotov, N. V. (1974) Muscovite-chlorite paleothermometer: Dokl. Akad. Nauk SSSR 222, 701–704.Google Scholar
  20. McDowell, S. D., and Elders, W. A. (1980) Authigenic layer silicated minerals in borehole Elmore 1, Salton Sea Geothermal field, California, USA: Contrib. Mineral. Petr. 74, 293–310.CrossRefGoogle Scholar
  21. Roots, M. (1991) Molar volume and pressure-dependent non-ideality of the clinochlore-amesite solid solution: Uppsala University, Department of Mineralogy and Petrology, Uppsala, Research Report no. 65, 22 p.Google Scholar
  22. Smith, J. T., and Ehrenberg, S. N. (1989) Correlation of carbon dioxide abundance with temperature in clastic hydrocarbon reservoirs: Relationship to inorganic chemical equilibrium: Marine Petr. Geol. 6, 129–135.CrossRefGoogle Scholar
  23. Stoessel, R. K. (1979) Refinements in a site-mixing model for illites: Geochim. Cosmochim. Acta 43, 1151–1159.CrossRefGoogle Scholar
  24. Stoessel, R. K. (1981) A regular solution site-mixing model for illites: Local electrostatic balance and the quasichemical approximation: Geochim. Cosmochim. Acta 45, 1733–1741.CrossRefGoogle Scholar
  25. Stoessel, R. K. (1984) Regular solution site-mixing model for chlorites: Clays & Clay Minerals 32, 205–212.CrossRefGoogle Scholar
  26. Tardy, Y., and Fritz, B. (1981) An ideal solid solution model for calculating solubility of clay minerals: Clay Miner. 16, 361–373.CrossRefGoogle Scholar
  27. Velde, B., and Medhioub, M. (1988) Approach to chemical equilibrium in diagenetic chlorites: Contrib. Mineral. Petr. 98, 122–127.CrossRefGoogle Scholar
  28. Walshe, J. L. (1986) A six-component chlorite solid solution model and conditions of chlorite formation in hydrothermal and geothermal systems: Econ. Geol. 81, 681–703.CrossRefGoogle Scholar
  29. Wiewiora, A., and Weiss, Z. (1990) Crystallochemical classification of phyllosilicates based on the unified system of projection of chemical composition: II. The chlorite group: Clay Miner. 25, 83–92.CrossRefGoogle Scholar

Copyright information

© The Clay Minerals Society 1992

Authors and Affiliations

  • P. Aagaard
    • 1
  • J. S. Jahren
    • 1
  1. 1.Department of GeologyUniversity of OsloOslo 3Norway

Personalised recommendations