Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by PAVESE, A. Articles by IBBERSON, R. Search for Related Content GeoRef GeoRef Citation

Deprotonation and order-disorder reactions as a function of temperature in a phengite 3T (Cima Pal, western Alps) by neutron diffraction and Mössbauer spectroscopy

¹ Dipartimento Scienze della Terra, Università degli Studi di Milano, Via Botticelli 23, I-20133 Milano, Italy
² National Research Council, IDAP, Via Mangiagalli 34, I-20133 Milano, Italy
³ Dipartimento Scienze Mineralogiche e Petrologiche, Università degli Studi di Torino, Via Valperga Caluso 35, I-10125 Torino, Italy
⁴ Dipartimento di Chimica Inorganica, Metallorganica e Analitica, Università di Padova, Via Loredan 4, I-35131 Padova, Italy
⁵ Rutherford Appleton Laboratory — ISIS — Chilton, Didcot - Oxfordshire, OX11 0QX UK

^* E-mail: alessandro.pavese{at}unimi.it

The results on deprotonation and cation partitioning as a function of temperature in the tetrahedral and octahedral sites of a phengite 3T, (K_0.94Na_0.02)_0.96 (Al_1.43Mg_0.33Fe_0.25)_2.01(Si_3.47Al_0.53)₄O₁₀(OH)₂, from Cima Pal (western Alps) are presented and discussed. They have been obtained by a synergic approach based on neutron powder diffraction from 293 K to 873 K, and on Mössbauer spectroscopy at ambient conditions, of the sample before and after heating. Order is observed at room temperature in both tetrahedral (Si fully occupies T1) and octahedral (Al almost fills M2) sites. Upon heating, deprotonation [mainly according to the reaction 2[(OH)^- + Fe²⁺] 2O^2- + 2Fe³⁺ + H₂], Fe oxidation and inter-site cation re-ordering reactions take place. Al moves by ~ 0.1 atoms from M2 to M3, and is replaced by Mg and Fe; Fe²⁺ and Fe³⁺ occupy different M-sites, after cooling, whereas Fe²⁺ was partitioned on two sites, one site shared with Fe³⁺, before heating.

Key-words: phengites, neutron powder diffraction, Mössbauer spectroscopy, cation partitioning..

This article has been cited by other articles:

				G. Cibin, G. Cinque, A. Marcelli, A. Mottana, and R. Sassi The octahedral sheet of metamorphic 2M1-phengites: A combined EMPA and AXANES study American Mineralogist, February 1, 2008; 93(2-3): 414 - 425. [Abstract] [Full Text] [PDF]

				N. Curetti, G. Ferraris, and G. Ivaldi Correlation between crystallization pressure and structural parameters of phengites American Mineralogist, February 1, 2008; 93(2-3): 451 - 455. [Abstract] [Full Text] [PDF]

				A. Pavese, N. Curetti, V. Diella, D. Levy, M. Dapiaggi, and U. Russo P-V and T-V Equations of State of natural biotite: An in-situ high-pressure and high-temperature powder diffraction study, combined with Mossbauer spectroscopy American Mineralogist, July 1, 2007; 92(7): 1158 - 1164. [Abstract] [Full Text] [PDF]