Deprotonation and order-disorder reactions as a function of temperature in a phengite 3T (Cima Pal, Western Alps) by neutron diffraction and Mossbauer spectroscopy
Deprotonation and order-disorder reactions as a function of temperature in a phengite 3T (Cima Pal, Western Alps) by neutron diffraction and Mossbauer spectroscopy (in Special issue dedicated to the memory of Luciano Ungaretti, Maria Chiara Domeneghetti (prefacer))
European Journal of Mineralogy (April 2003) 15 (2): 357-363
For a phengite 3T (K (sub 0.94) Na (sub 0.02) )(Al (sub 1.43) Mg (sub 0.33) Fe (sub 0.25) ) (Si (sub 3.47) Al (sub 0.53) )O (sub 10) (OH) (sub 2) , from Cima Pal, order is observed at room T in both tetrahedral (Si fully occupies T1) and octahedral (Al almost fills M2) sites. On heating to 873 K, deprotonation, Fe oxidation and inter-site cation re-ordering reactions occur. Al moves by approximately 0.1 atoms from M2 to M3, and is replaced by Mg and Fe; Fe (super 2+) and Fe (super 3+) occupy different M sites, after cooling, whereas Fe (super 2+) was partitioned on two sites, one shared with Fe (super 3+) , before heating.