A-Na B-(NaMg) C-Mg5 Si8 O22 (OH,D)2 amphibole was hydrothermally synthesized at 850 °C and 0.3 GPa. SEM, EPMA, and X-ray powder-diffraction data showed the experimental product to consist of a high amphibole yield (90–95%), plus minor quartz and rare enstatite. Neutron powder diffraction data were collected using a time-of-flight diffractometer at room T and at 8 K, respectively, and structure refinement was carried out using the Rietveld method. The space group of the amphibole is P21/m at both temperatures, as confirmed by the presence of b-type reflections (h + k= 2n+ 1). FTIR OH- and OD-stretching spectra at both room and low T(30 K) show two main absorptions, which are assigned to two non-equivalent OH groups in the struc-ture, and a third lower-frequency band, assigned to A-site vacant environments (local cummingtonite environments). At room- and low-T, the cell parameters are (in Å): a 9.7188(1) and 9.7016(2), b 17.9385(3) and 17.8953(4), c 5.2692(1) and 5.2574(1); beta (°) is 102.526(1) and 102.597(2). Cell volumes (Å3) are 896.78(2) at room T and 890.80(2) at 8 K, with a relative reduction of less than 1%. Accurate structural positions for the hydrogen atoms were obtained from diffraction data. The O5A-O6A-O5A and O5B-O6B-O5B angles, diagnostic of the A- and B-chains kinking along c, are 190.0° and 159.2° at 293 K and 193.8° and 156.8° at 8 K, respectively. The orientation of the thermoelastic strain ellipsoid was calculated and the principal unit-strain tensor components are reported. A comparison between the low-temperature data reported here and the high-temperature data for a similar amphibole composition, reported by Cámara et al. (2003) up to 643 K, is presented.

Low-T neutron powder-diffraction and synchrotron-radiation IR study of synthetic amphibole Na(NaMg)Mg5Si8O22(OH)2 / G. Iezzi, G.D. Gatta, W. Kokelmann, G. Della Ventura, R. Rinaldi, W. Schäfer, M. Piccinini, F. Gaillard. - In: GEOPHYSICAL RESEARCH ABSTRACTS. - ISSN 1607-7962. - 7:(2005), pp. 10955-10955.

Low-T neutron powder-diffraction and synchrotron-radiation IR study of synthetic amphibole Na(NaMg)Mg5Si8O22(OH)2

G.D. Gatta
Secondo
;
2005

Abstract

A-Na B-(NaMg) C-Mg5 Si8 O22 (OH,D)2 amphibole was hydrothermally synthesized at 850 °C and 0.3 GPa. SEM, EPMA, and X-ray powder-diffraction data showed the experimental product to consist of a high amphibole yield (90–95%), plus minor quartz and rare enstatite. Neutron powder diffraction data were collected using a time-of-flight diffractometer at room T and at 8 K, respectively, and structure refinement was carried out using the Rietveld method. The space group of the amphibole is P21/m at both temperatures, as confirmed by the presence of b-type reflections (h + k= 2n+ 1). FTIR OH- and OD-stretching spectra at both room and low T(30 K) show two main absorptions, which are assigned to two non-equivalent OH groups in the struc-ture, and a third lower-frequency band, assigned to A-site vacant environments (local cummingtonite environments). At room- and low-T, the cell parameters are (in Å): a 9.7188(1) and 9.7016(2), b 17.9385(3) and 17.8953(4), c 5.2692(1) and 5.2574(1); beta (°) is 102.526(1) and 102.597(2). Cell volumes (Å3) are 896.78(2) at room T and 890.80(2) at 8 K, with a relative reduction of less than 1%. Accurate structural positions for the hydrogen atoms were obtained from diffraction data. The O5A-O6A-O5A and O5B-O6B-O5B angles, diagnostic of the A- and B-chains kinking along c, are 190.0° and 159.2° at 293 K and 193.8° and 156.8° at 8 K, respectively. The orientation of the thermoelastic strain ellipsoid was calculated and the principal unit-strain tensor components are reported. A comparison between the low-temperature data reported here and the high-temperature data for a similar amphibole composition, reported by Cámara et al. (2003) up to 643 K, is presented.
Settore GEO/09 - Georisorse Miner.Appl.Mineral.-Petrogr.per l'amb.e i Beni Cul
Article (author)
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/7772
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus ND
  • ???jsp.display-item.citation.isi??? ND
social impact