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A high-pressure structural study of lawsonite using angle-dispersive powder-diffraction methods with synchrotron radiation

Published online by Cambridge University Press:  05 July 2018

A. R. Pawley*
Affiliation:
Department of Earth Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK
D. R. Allan
Affiliation:
Department of Physics and Astronomy, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, UK
*

Abstract

Structural refinements of lawsonite have been obtained at pressures up to 16.5 GPa using angle-dispersive powder diffraction with synchrotron radiation on a natural sample contained in a diamond anvil cell. Lawsonite compresses smoothly and relatively isotropically up to 10 GPa. Its bulk modulus is 126.1(6) GPa (for K’ = 4), consistent with previous results. A trend of decreasing Si–O–Si angle indicates that compression is accommodated partly through the narrowing of the cavities containing Ca and H2O in the [001]ortho direction. At 10–11 GPa there is a phase transition from Cmcm to P21/m symmetry. The occurrence of a mixed-phase region, spanning >1 GPa, indicates that the transition is first order in character. The phase transition occurs through a shearing of (010)ortho sheets containing AlO6 octahedral chains in the [100]ortho direction, which causes an increase in βmono. Across the transition, the number of oxygens coordinated to Ca increases from 8 to 9, causing an increase in the average Ca–O bond length. The compressibility of P21/m lawsonite could not be determined due to solidification of the methanol/ethanol pressure-transmitting medium. On the basis of an experiment in which the P21/m lawsonite structure was heated to 200°C at 12.0 GPa, we predict a shallow positive P-T slope for the phase transition, and therefore no stability field for P21/m lawsonite in the Earth.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2001

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References

Baur, W.H. (1978) Crystal structure refinement of lawsonite. Amer. Mineral., 63, 311–5.Google Scholar
Brunet, F., Allan, D.R., Redfern, S.A.T., Angel, R.J., Miletich, R., Reichmann, H.J., Sergent, J. and Hanfland, M. (1999) Compressibility and thermal expansivity of synthetic apatites, Ca5(PO4)3X with X = OH, F and Cl. Eur. J. Mineral., 11, 1023–35.CrossRefGoogle Scholar
Chinnery, N.J., Pawley, A.R. and Clark, S.M. (2000) The equation of state of lawsonite to 7 GPa and 873 K and calculation of its high pressure stability. Amer. Mineral., 85, 1001–8.CrossRefGoogle Scholar
Comodi, P. and Zanazzi, P.F. (1996) Effects of temperature and pressure on the structure of lawsonite. Amer. Mineral., 81, 833–41.CrossRefGoogle Scholar
Daniel, I., Fiquet, G., Gillet, P., Schmidt, M.W. and Hanfland, M. (1999) P-V-T equation of state of lawsonite. Phys. Chem. Miner., 26, 406–14.CrossRefGoogle Scholar
Daniel, I., Fiquet, G., Gillet, P., Schmidt, M.W. and Hanfland, M. (2000) High-pressure behaviour of lawsonite: a phase transition at 8.6 GPa. Eur. J. Mineral., 12, 721–33.CrossRefGoogle Scholar
Grevel, K.D., Nowlan, E.U., Fasshauer, D.W. and Burchard, M. (2000) In situ X-ray diffraction investigation of lawsonite and zoisite at high pressures and temperatures. Amer. Mineral., 85, 206–16.CrossRefGoogle Scholar
Hazen, R.M. and Finger, L.W. (1979) Polyhedral tilting: A common type of pure displacive phase transition and its relationship to analcite at high pressure. Phase Trans., 1, 122.CrossRefGoogle Scholar
Hazen, R.M. and Finger, L.W. (1983) High-pressure and high- temperature crystallographic study of the gillespite I-II phase tranistion. Amer. Mineral., 68, 595603.Google Scholar
Hazen, R.M. and Prewitt, C.T. (1977) Effects of temperature and pressure on interatomic distances in oxygen- based minerals. Amer. Mineral., 62, 309–15.Google Scholar
Holland, T.J.B., Redfern, S.A.T. and Pawley, A.R. (1996) Volume behavior of hydrous minerals at high pressure and temperature: II. Compressibilities of lawsonite, zoisite, clinozoisite and epidote. Amer. Mineral., 81, 341–8.CrossRefGoogle Scholar
Larson, A.C. and Von Dreele, R.B. (1994) GSAS, General Structure Analysis System. Los Alamos National Laboratory, LAUR, 86748.Google Scholar
Libowitzky, E. and Armbruster, T. (1995) Low-temperature phase transitions and the role of hydrogen bonds in lawsonite. Amer. Mineral., 80, 1277–85.CrossRefGoogle Scholar
Libowitzky, E. and Rossman, G.R. (1996) FTIR spectroscopy of lawsonite between 82 and 325 K. Amer. Mineral., 81, 1080–91.CrossRefGoogle Scholar
Nelmes, R.J. and McMahon, M.I. (1994) High-pressure powder diffraction on synchrotron sources. J. Synch. Radiat., 1, 6973.CrossRefGoogle ScholarPubMed
Pawley, A.R. (1994) The pressure and temperature stability limits of lawsonite: Implications for H2O recycling in subduction zones. Contrib. Mineral. Petrol., 118, 99108.CrossRefGoogle Scholar
Pawley, A.R., Redfern, S.A.T. and Holland, T.J.B. (1996) Volume behavior of hydrous minerals at high pressure and temperature: I. Thermal expansion of lawsonite, zoisite, clinozoisite and diaspore. Amer. Mineral., 81, 335–40.CrossRefGoogle Scholar
Pawley, A.R., Chinnery, N.J. and Clark, S.M. (1998) Volume measurements of zoisite at simultaneously elevated pressure and temperature. Amer. Mineral., 83, 1030–6.CrossRefGoogle Scholar
Piltz, R.O., McMahon, M.I., Crain, J., Hatton, P.D., Nelmes, R.J., Cernik, R.J. and Bushnell-Wye, G. (1992) An Imaging Plate System for High-Pressure Powder Diffraction: The Data Processing Side. Rev. Sci. Instrum., 63, 700.CrossRefGoogle Scholar
Schmidt, M.W. (1995) Lawsonite: upper pressure stability and formation of higher density hydrous phases. Amer. Mineral., 80, 1286–92.CrossRefGoogle Scholar
Scott, H.P. and Williams, Q. (1999) An infrared spectroscopic study of lawsonite to 20 GPa. Phys. Chem. Miner. 26, 437–45.CrossRefGoogle Scholar