Contributions to Mineralogy and Petrology

, Volume 30, Issue 3, pp 196–215 | Cite as

Synthesis and stability of micas in the system K2O-MgO-SiO2-H2O and their relations to phlogopite

  • F. Seifert
  • W. Schreyer
Article

Abstract

A series of alumina-free micas was synthesized hydrothermally in the potassium-poor portion of the system K2O-MgO-SiO2-H2O. One end member of this series has the composition KMg2.5[Si4O10](OH)2, which, because of its octahedral occupancy, is intermediate between the dioctahedral and trioctahedral micas.

From this end member a series of mica solid solutions extends towards more Mg-rich compositions. Single phase micas were obtained along the substitution line 2Mg for Si which appears to involve incorporation of part of the Mg in tetrahedral sites. It leads to a theoretical end member with a structural formula KMg3[Si3.5Mg0.5O10](OH)2. Solid solutions containing up to 75 mole % of this theoretical end member could be synthesized. The observed densities, water contents, and a one-dimensional Fourier synthesis are consistent with the assumed substitution.

At 1 kb fluid pressure and 620° C the Si-rich end member KMg2.5[Si4O10](OH)2 decomposes to a more Mg-rich mica, the roedderite phase K2Mg5Si12O30, liquid, and H2O-rich vapor. With increasing Mg-content the thermal stability of the mica solid solutions increases up to 860°C at a composition of about K2O·6.2MgO·7.4SiO2·2H2O, i.e. KMg2.8[Si3.7Mg0.3O10](OH)2. This mica disintegrates directly into forsterite + liquid + H2O-rich vapor. The mica phase richest in Mg with a composition of about K2O·6.5MgO·7.25SiO2·2H2O, i.e. KMg2.875 [Si3.625Mg0.375O10](OH)2, breaks down at 765° C into forsterite, a more Si-rich mica, liquid, and H2O-rich vapor.

This binary series of alumina-free micas forms a complete series of ternary solid solutions with normal phlogopite, KMg3[Si3AlO10](OH)2. Analyses of some natural phlogopites showing Si in excess of 3.0 (up to 3.18) per formula unit can be explained through this ternary miscibility range.

Keywords

SiO2 Solid Solution Fluid Pressure Forsterite Formula Unit 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Bailey, D. K.: Temperatures and vapor composition in carbonatite and kimberlite. Carnegie Inst. Wash. Year Book 63, 79–81 (1964).Google Scholar
  2. Carmichael, I. E. S.: The mineralogy and petrology of the volcanic rocks from the Leucite Hills, Wyoming, Contr. Mineral. and Petrol. 15, 24–66 (1967).Google Scholar
  3. Cross, W.: Igneous rocks of the Leucite Hills and Pilot Butte, Wyoming. Am. J. Sci. 4, 115–141 (1897).Google Scholar
  4. Crowley, M. S., Roy, R.: Crystalline solubility in the muscovite and phlogopite groups. Am. Mineralogist 49, 348–362 (1964).Google Scholar
  5. Daimon, N., Suwa, K., Yamamoto, K.: Synthesis of Mn mica. Kogyo Kagaku Zasshi 64, 1906–1908 (1961).Google Scholar
  6. Flink, G.: On the minerals from Narsarsuk on the Firth of Tungdiarfik in southern Greenland. Medd. Groenland 24, 110–115 (1901).Google Scholar
  7. Foster, M. D.: Interpretation of the composition of trioctahedral micas. US Geol. Surv. Profess. Papers 354-B, 1–49 (1960).Google Scholar
  8. Nordenskjöld, G.: Om mineral fran drushal vid Taberg i Vermland. Geol. För. Förh. 12, 348–358 (1890).Google Scholar
  9. Pawlowska, J., Bittmarowa, M.: Phlogopite rock with apatite at Kapaniec (Izerskie Mountains). Prizgl. Geol. 15, 61–63 (1967).Google Scholar
  10. Radoslovich, E. W.: The cell dimensions and symmetry of layer lattice silicates. II. Regression relations. Am. Mineralogist 47, 617 (1962).Google Scholar
  11. Rimsaite, J.: On micas from magmatic and metamorphic rocks. Beitr. Min. Petrol. 10, 152–183 (1964).Google Scholar
  12. Roedder, E. W.: The system K2O-MgO-SiO2. Am. J. Sci. 249, 81–130, 224–248 (1951).Google Scholar
  13. Schairer, J. F., Bowen, N. L.: The system K2O-Al2O3-SiO2. Am. J. Sci. 253, 681–746 (1955).Google Scholar
  14. Sclar, C. B., Carrison, L. C., Schwartz, C. M.: High-pressure synthesis and stability of a new hydronium-bearing layer silicate in the system MgO-SiO2-H2O. Trans. Am. Geophys. Union 46, 184 (1965).Google Scholar
  15. Seifert, F.: X-ray powder data for MgAl-celadonite (leucophyllite) from Barcza, Poland. Contr. Mineral. and Petrol. 19, 93–96 (1968).Google Scholar
  16. —, Schreyer, W.: Synthesis of a new mica, KMg2.5[Si4O10](OH)2. Am. Mineralogist 50, 1114–1118 (1965).Google Scholar
  17. — —: Fluide Phasen im System K2O-MgO-SiO2-H2O und ihre mögliche Bedeutung für die Entstehung ultrabasischer Gesteine. Ber. Bunsenges. Phys. Chem. 70, 1045–1050 (1966).Google Scholar
  18. — —: Die Möglichkeit der Entstehung ultrabasischer Magmen bei Gegenwart geringer Alkalimengen. Geol. Rundschau 57, 349–362 (1968a).Google Scholar
  19. - - Synthesis and stability of micas in the system K2O-MgO-SiO2 -H2O and their relations to phlogopite. International Mineralogical Association, Sixth General Meeting Abstracts 42–43, Prague (1968b).Google Scholar
  20. — —: Stability relations of K2Mg5Si12O30, an end member of the roedderite-merrihueite group of meteoritic minerals. Contr. Mineral. and Petrol. 22, 190–207 (1969).Google Scholar
  21. Smith, J. V., Yoder, H. S., Jr.: Experimental and theoretical studies of the mica polymorphs. Mineral. Mag. 31, 209–235 (1956).Google Scholar
  22. Stirland, D. J., Thomas, A. G., Moore, N. C.: Observations on thermal transformations in alumina. Brit. Ceram. Soc. Trans. 57, 69–84 (1958).Google Scholar
  23. Takeda, H., Donnay, J. D. H.: Structure of a synthetic lithiumfluor mica. (Abstract) Am. Mineralogist 50, 293 (1965).Google Scholar
  24. Velde, B.: Phengite micas: synthesis, stability, and natural occurrence. Am. J. Sci. 263, 886–913 (1965).Google Scholar
  25. Wade, A., Prider, R. T.: The leucite-bearing rocks of the West Kimberley area, Western Australia. Quart. J. Geol. London 96, 39–98 (1940).Google Scholar
  26. Williams, A. F.: The genesis of the diamond I, II. London 1932.Google Scholar
  27. Winchell, A. N.: The biotite system. Am. Mineralogist 20, 773–779 (1935).Google Scholar
  28. Wise, W. S., Eugster, H. P.: Celadonite: synthesis, thermal stability, and occurrence. Am. Mineralogist 49, 1031–1083 (1964).Google Scholar
  29. Wones, D. R., Eugster, H. P.: Stability of biotite: experiment, theory, and application. Am. Mineralogist 50, 1228–1272 (1965).Google Scholar
  30. Yoder, H. S., Jr., Eugster, H. P.: Phlogopite synthesis and stability range. Geochim. Cosmochim. Acta 6, 157–185 (1954).Google Scholar
  31. — —: Synthetic and natural muscovites, Geochim. Cosmochim. Acta 8, 225–280 (1955).Google Scholar

Copyright information

© Springer-Verlag 1971

Authors and Affiliations

  • F. Seifert
    • 1
  • W. Schreyer
    • 1
  1. 1.Institut für Mineralogie der Ruhr-UniversitätBochum

Personalised recommendations