Hostname: page-component-8448b6f56d-42gr6 Total loading time: 0 Render date: 2024-04-23T10:45:25.230Z Has data issue: false hasContentIssue false
  • English
  • Français

Muscovite solid solutions in the system K2O-MgO-FeO-Al2O3-SiO2-H2O: an experimental study at 2 kbar PH2O and comparison with natural Li-Free white micas

Published online by Cambridge University Press:  05 July 2018

Gilles Monier  and
Jean-Louis Robert
Gilles Monier
Affiliation:
Laboratoire de Pérologie, Université d'Orléans, 45046 Orléans Cedex, France Centre de Recherche sur la Synthèse et Chimie des Minéraux, G.I.S.C.N.R.S.-B.R.G.M., 1A rue de la Férollerie, 45071 Orléans Cedex 2, France
Get access Rights & Permissions [Opens in a new window]

Abstract

This paper presents the results of an experimental study of muscovite solid solutions in the system K2O-M2+O-Al2O3-SiO2-H2O-(HF), with M2+ = Mg2+ or Fe2+ in the temperature range 300-700°C under 2 kbar PH2O. Muscovite solid solutions can be described, in this system, as the result of two substitutions. One is the phengitic substitution (x), which preserves the pure dioctahedral character of the mica; the second is the biotitic substitution (y), which leads to trioctahedral micas and does not change the composition of the tetrahedral layer Si3Al. The general formula of muscovite in this system is K(Al2−x−2y∕3M2+x+y□1−y∕3)(Si3+xAl1−x)O10(OH,F)2. Both substitutions x and y are more extensive at lower temperatures. The extent of solid solution decreases drastically with increasing temperature.

For T > 600°C, the phengitic substitution (x) becomes negligible, but some biotitic substitution (y) persists. This unsymmetrical decrease of the solid solution of muscovite with increasing temperature is similar to that previously observed in phlogopite, the micas with a tetrahedral layer composition of Si3Al being the most stable. The behaviour of muscovite solid solutions in the ferrous system is qualitatively identical to that observed in the magnesian one, but the extent of solid solution is smaller than with Mg2+. Fluorine neither changes the size nor the shape of the solid solution fields but increases their stability by about 50°C.

A comparison of these experimental results with data on natural muscovites is presented. Most natural primary (magmatic) granitic muscovites lie very close to the muscovite end member, in agreement with their high-temperature origin. Low-temperature muscovites (300–400°C), typically muscovites from hydrothermally altered granitic rocks, can have high x and y values. The rate of the biotitic substitution y can reach 0.6, which corresponds to an octahedral occupancy of 2.2 atoms per formula unit (based on 11 oxygens), consistent with the experimental data.

Keywords

muscovitephengitesolid solutioncrystal-chemistryexperimental mineralogygraniteshydrothermal alteration
Type
Mineralogy
Information
Mineralogical Magazine , Volume 50 , Issue 356 , June 1986 , pp. 257 - 266
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1986

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Anderson, J.L., and Rowley, M.C. (1981) Can. Mineral, 19, 83-101.Google Scholar
Burnol, L., Le Bel, L., and Lougnon, J. (1980) Chronique de la Recherche Minieie,Ed. B.R.G.M., France, no. 455, 36-59.Google Scholar
Chatterjee, N.D., and Johannes, W. (1974) Contrib. Mineral. Petrol, 48, 89-114.CrossRefGoogle Scholar
Crowley, M.S., and Roy, R. (1964) Am. Mineral, 49, 348-63.Google Scholar
Dudoignon, P., and Meunier, A. (1984) Colloquium ‘Geologie profonde de la France',Doc. B.R.G.M. no. 81-8, Ed. B.R.G.M., France, 87-107.Google Scholar
Floc'h, J.P. (1979) Bull. B.R.G.M.,France, Section 1, no. 2, 89-107.Google Scholar
Green, T.H. (1981) Contrib. Mineral. Petrol, 78, 452-8.CrossRefGoogle Scholar
Hamilton, D.L., and Henderson, C.M.B. (1968) Mineral. Mag, 36, 832-8.Google Scholar
Johan, Z., and Le Bel, L. (1980) Mineralisations liees aux granitoides, 26e C.G.I., Paris, 95–119.Google Scholar
Julliot, J.-Y. Volfinger, M., and Robert, J.-L. (1986) Submitted to Tschermaks Mineral. Petr. Mitt. Google Scholar
Lameyre, J. (1973) Bull. Soc. Geol. France, 7, XV, 3-4, 288-95.CrossRefGoogle Scholar
Le Bel, L. (1979a) These d'Etat, Univ. Lausanne, Switzerland, 160 pp.Google Scholar
Le Bel, L. (1979b) Bull. Mineral, 102, 35-41.Google Scholar
Le Fort, P. (1981) J. Geophys. Res. 86, B 11, 10545-68.Google Scholar
Massonne, H.J. (1981) Thesis, Bochum F.R.G., 211 pp.Google Scholar
Meunier, A., and Velde, B. (1962) Clay Minerals, 17, 285-99.CrossRefGoogle Scholar
Miller, C.F., Stoddard, E.F., Bradfish, L.J., and Dollase, W.A. (1981) Can. Mineral, 19, 25-34.Google Scholar
Monier, G. (1985) These d'Etat, Univ. Orleans, France, 299 pp.Google Scholar
Monier, G. and Robert, J.-L. (1985) Neues Jahrb. Mineral. Abh, 152, 147-61.Google Scholar
Mergoil-Daniel, J., and Labernardiere, H. (1984) Bull. Mineral, 107, 55-68.Google Scholar
Munoz, J.L., and Ludington, S.D. (1977) Am. Mineral, 62, 304-8.Google Scholar
Neiva, A.M.R. (1982) Metallization Associated with Acid Magmatism (A. M. Evans, ed.). Wiley, New York, 243-59.Google Scholar
Robert, J.-L. (1973) These 3e cycle, Univ. Paris Sud, France, 73 pp.Google Scholar
Robert, J.-L. (1976) Chem. Geol, 17, 195-212.CrossRefGoogle Scholar
Robert, J.-L. (1981) These d'Etat, Univ. Paris XI, France, 206 pp.Google Scholar
Rutherford, M.J. (1973) J. Petrol, 14, 159-80.CrossRefGoogle Scholar
Shannon, R.P., and Prewitt, C.T. (1969) Ada Crystallogr. B25, 925-46.CrossRefGoogle Scholar
Shannon, R.P., and Prewitt, C.T. (1970. Ibid. B26, 1046-8.CrossRefGoogle Scholar
Speer, J.A. (1984) Reviews in Mineralogy M.S.A. Micas. Bailey Ed.,13, 299-356.Google Scholar
Velde, B. (1965) Am. J. Sci, 263, 886-913.CrossRefGoogle Scholar
Velde, B. (1967) Contrib. Mineral. Petrol, 14, 250-8.CrossRefGoogle Scholar
Velde, B. (1980) Am. Mineral, 65, 1277-82.Google Scholar
Yoder, H.S., and Eugster, H.P. (1954) Geochim. Cosmochim. Ada, 6, 157-85.CrossRefGoogle Scholar