Abstract
A member of the grunerite series (Fe6.685Mn0.142Ca0.110Mg0.096) (Si7.968Al0.016)O22(OH)2, has been transformed to clinoferrosilite, amorphous silica and water at 775° C and 500 bars Argon pressure. Single crystal photographs of an oriented intergrowth of the amphibole and pyroxene show that the clinoferrosilite retains the cristallographic a, b and c axes of the original grunerite in the I2/m orientation and has the cell dimensions: a=9.77, b=9.08, c=5.30 Å, β=109.5°; space group P21/c. Mössbauer resonance spectroscopy confirmed the identity of the olinoferrosilite.
A transformation mechanism requires a minimum of ionic movements in an acceptor region (7/8 of the total crystal), where pyroxene is formed by expulsion of protons and acceptance of Fe2+ ions; simultaneous destruction of donor regions provide the Fe2+ ions, the residue being silica and water. The formation of metastable clinoferrosilite rather than fayalite and quartz indicates the strong structural control imposed by the host grunerite structure on the nature of the transformation products.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Akimoto, S., Katsura, T., Syono, Y., Fujisawa, H., Komada, E.: Polymorphic transition of pyroxenes FeSiO3 and CoSiO3 at high pressures and temperatures. J. Geophys. Res. 70, 5269–5277 (1965).
Burnham, C. W.: Ferrosilite. Geophys. Lab. Annual Rep., Carnegie Institution Y. B. 64, 202–204 (1965).
—: Ferrosilite. Geophys. Lab. Annual Rep., Carnegie Institution Y.B. 65, 285–290 (1966).
Dundon, R., Lindsley, D. H.: Mössbauer study of synthetic Ca-Fe-clinopyroxenes. Geophys. Lab. Annual Rep., Carnegie Institution Y.B. 66, 366–369 (1968).
Freeman, A. G., Frazer, F. W.: A pseudo polymorphic transition: the amphibole→pyroxene reaction. Nature 220, 67–68 (1968).
—, Taylor, H. F. W.: Die Entwässerung von Tremolit. Silikat Tech. 11, 390–392 (1960).
Ghose, S., Hafner, S. S.: Application of 57Fe Mössbauer resonance to silicates, in Application of Nuclear and Electronic Resonance Spectroscopy in Mineralogy. Am. Geol. Inst., Washington, D. C. GH1–31 (1968).
Hodgson, A. A., Freeman, A. G., Taylor, H. F. W.: The thermal decomposition of amosite. Mineral. Mag. 35, 445–463 (1965).
Lindsley, D. H.: Pressure-temperature relations in the system FeO-SiO2. Geophys. Lab. Annual Rep., Carnegie Institution Y.B. 65, 226–230 (1966).
Marzolf, J. G., Dehn, J. T., Salmon, J. F.: Mössbauer studies of tektites, pyroxenes, and olivines. Advanc. Chem. Ser. 68, 61–85 (1967).
Mueller, R. F.: Compositional characteristics and equilibrium relations in mineral assemblages of a metamorphosed Iron Formation. Am. J. Sci. 258, 449–497 (1960).
Schoen, R., Lee, D. E.: Successful separation of silt-size minerals in heavy liquids. U. S. Geol. Surv. Profess. Papers 501-B, B 154–157 (1964).
Smith, D.: Stability of iron-rich orthopyroxenes. Geophys. Lab. Annual Rep., Carnegie Institution Y. B. 68, 229–231 (1970).
Tuttle, O. F.: Two pressure vessels for silicate-water studies. Bull. Geol. Soc. Am. 60, 1727–1739 (1949).
Viswanathan, K., Ghose, S.: The effect of Mg2+-Fe2+ substitution on the cell dimensions of cummingtonites. Am. Mineralogist 50, 1106–1112 (1965).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Ghose, S., Weidner, J.R. Oriented transformation of grunerite to clinoferrosilite at 775° C and 500 bars Argon pressure. Contr. Mineral. and Petrol. 30, 64–71 (1971). https://doi.org/10.1007/BF00373369
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00373369