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Long-range Al,Si equilibrium configuration in Sr feldspar treated at high temperatures

Published online by Cambridge University Press:  05 July 2018

P. Benna  and
E. Bruno
P. Benna*
Affiliation:
Dipartimento di Scienze Mineralogiche e Petrologiche, Via Valperga Caluso 35, I-10125 Torino, Italy
E. Bruno
Affiliation:
Dipartimento di Scienze Mineralogiche e Petrologiche, Via Valperga Caluso 35, I-10125 Torino, Italy
*
*E-mail: [email protected]
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Abstract

Single crystals of Sr feldspar (SrAl2Si2O8, space group: I2/c) were treated isothermally in the temperature range between 1410 and 1640°C, in order to determinate the evolution of the Al,Si configurations at equilibrium with thermal treatments. X-ray intensity data collection and structural refinement were performed on the quenched crystals. Significant modifications were observed in the average tetrahedral distances and therefore in Qod values.

Two different series of thermal treatments were performed: (1) a crystal of ordered Sr feldspar (Qod= 0.85) was progressively disordered at 1560°C (Qod = 0.82), at 1610°C (Qod = 0.74) and at 1640°C (Qod = 0.69); (2) another crystal with Qod = 0.72 (obtained by annealing a glass at T =1625°C), was ordered at T = 1600° (Qod = 0.75).

As already observed in anorthite quenched from 1530°C (Qod = 0.78), also in Sr feldspar, annealing near Tmelt, caused significant disorder in the Al-Si configuration (Qod = 0.69).

Observations by transmission electron microscopy show an increase in the average size of the i-type antiphase domains up to 5000Å in the samples quenched from 1640°C, in comparison with samples annealed at 1450°C (∼ 2000 Å). The modifications observed in the Al,Si configurations are due to intradomain disorder.

Keywords

strontium feldsparcrystal structurethermal treatments
Type
Research Article
Information
Mineralogical Magazine , Volume 70 , Issue 1 , February 2006 , pp. 65 - 71
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2006

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References

Angel, R.J., Carpenter, M.A. and Finger, L.W. (1990) Structural variation associated with compositional variation and order-disorder behavior in anorthite-rich feldspar. American Mineralogist, 75, 150–162.Google Scholar
Bambauer, H.U. and Nager, H.E. (1981) Gitterkonstanten und displazive Transformationen synthetischer Erdalkalifeldspäte. I. System Ca[Al2Si2Og]-Sr[Al2Si2O8]-Ba[Al2Si2O8]. Neues Jahrbuch für Mineralogie Abhandlungen, 141, 225–239.Google Scholar
Bema, P., Zanini, G. and Bruno, E. (1985) Cellparameters of thermally treated anorthite. Al, Si configurations in the average structures of the high temperature calcic plagioclases. Contributions to Mineralogy and Petrology, 90, 381–385.Google Scholar
Benna, P., Tribaudino, M. and Bruno, E. (1995) Al, Si ordering in Sr-feldspar SrAl2Si208: IR, TEM and single-crystal XRD evidences. Physics and Chemistry of Minerals, 22, 343–350.CrossRefGoogle Scholar
Benna, P., Tribaudino, M. and Bruno, E. (1996) The structure of ordered and disordered Pb-feldspar (PbAl2Si2O8). American Mineralogist, 81, 1337–1343.CrossRefGoogle Scholar
Biggar, G.M. and O'Hara, M.J. (1969) A comparison of gel and glass starting materials for phase equilibrium studies. Mineralogical Magazine, 36, 198–205.CrossRefGoogle Scholar
Bruno, E., Chiari, G. and Facchinelli, A. (1976) Anorthite quenched from 1530°C. I. Structure refinement. Ada Crystallographica, B32, 3270–3280.Google Scholar
Carpenter, M.A. (1991a) Mechanisms and kinetics of Al,Si ordering in anorthite: I. Incommensurate structure and domain coarsening. American Mineralogist, 76, 1110–1119.Google Scholar
Carpenter, M.A. (19916) Mechanisms and kinetics of Al,Si ordering in anorthite: H Energetics and a Ginzburg-Landau rate law. American Mineralogist, 76, 1120–1133.Google Scholar
Carpenter, M.A. (1992) Equilibrium thermodynamics of Al/Si ordering in anorthite. Physics and Chemistry of Minerals, 19, 1–24.CrossRefGoogle Scholar
Carpenter, M.A. and Ferry, J.M. (1984) Constraints on the thermodynamic mixing properties of plagioclase feldspars. Contributions to Mineralogy and Petrology, 87, 138–148.CrossRefGoogle Scholar
Carpenter, M.A., Angel, R.J. and Finger, L.W. (1990) Calibration of Al/Si order variations in anorthite. Contributions to Mineralogy and Petrology, 104, 471–480.CrossRefGoogle Scholar
Chiari, G., Facchinelli, A. and Bruno, E. (1978) Anorthite quenched from 1530°C. II. Discussion. Ada Crystallographica, B34, 1757–1764.Google Scholar
Courtial, P., Tequi, C. and Richet, P. (2000) Thermodynamics of diopside, anorthite, pseudowol-lastonite, CaMgGeO4 olivine, and åkermanite up to near the melting point. Physics and Chemistry of Minerals, 27, 242–250.CrossRefGoogle Scholar
Malcherek, T., Carpenter, M.A., Kroll, H. and Salje, E.K.H. (1999) Cation ordering in BaAl2Ge2O8-feldspar: implications for the Iī-Cī phase transition in anorthite. Physics and Chemistry of Minerals, 26, 354–366.CrossRefGoogle Scholar
Malcherek, T., Kroll, H. and Salje, E.K.H. (2000) Al,Ge cation ordering in BaAl2Ge2O8-feldspar: mono-domain ordering kinetics. Physics and Chemistry of Minerals, 27, 203–212.CrossRefGoogle Scholar
North, A.C.T., Phillips, D.C. and Mathews, F.S. (1968) A semi-empirical method of absorption correction. Ada Crystallographica, A24, 351–359.Google Scholar
Phillips, B.L., Kirkpatrick, R.J. and Carpenter, M.A. (1992) Investigation of short-range ALSi order in synthetic anorthite by 29Si MAS NMR spectroscopy. American Mineralogist, 77, 484–494.Google Scholar
Richet, P., Ingrin, J., Mysen, B.O., Courtial, P. and Gillet, P. (1994) Premelting effects in minerals: an experimental study. Earth and Planetary Science Letters, 121, 589–600.Google Scholar
Sheldrick, G.M. (1997) SHELXL-97 - A program for crystal structure refinement. University of Gottingen, Germany, Release 97–2.Google Scholar
Tribaudino, M., Benna, P. and Bruno, E. (1998) Structural variations induced by thermal treatment in Pb-feldspar (PbAl2Si2O8). American Mineralogist, 83, 159–166.CrossRefGoogle Scholar
Wood, B.J. and Holloway, J.R. (1984) A thermodynamic model for subsolidus equilibria in the system CaO-MgO-Al2O3-SiO2 . Geochimica et Cosmochimica Ada, 48, 159–176.CrossRefGoogle Scholar