• journal_title：American Mineralogist
• Contributor：Anna Yu. Likhacheva ; Sergey V. Goryainov ; Taras A. Bul’bak
• Publisher：Mineralogical Society of America
• Date：2013-01-01
• Format：text/html
• Language：en
• Identifier：10.2138/am.2013.4199
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：98
• issue：1
• firstpage：181
• section：Articles

The elastic and structural behavior of natural cordierite compressed in aqueous medium up to 6 GPa was studied by means of in situ synchrotron powder diffraction with a diamond-anvil cell. In the range between 1–4 GPa the elastic behavior is regular and slightly anisotropic, with linear compressibilities β_a:β_b:β_c = 4:4:5, the most rigid a–b plane coinciding with the orientation of 6-membered rings. A distinct decrease of compressibility in the range of 4–5 GPa indicates a pressure-induced hydration (PIH), which is confirmed by the structure refinements. The addition of about 60% of the initial water content into the cordierite channels proceeds through positional disordering of the H₂O sites inside the channel cavity and a stepwise filling of the H₂O position inside the 6-membered rings, leading to the phase transition at about 4.7 GPa. The appearance of H₂O molecules inside 6-membered rings prevents their contraction and even causes their slight enlargement along the a direction, apparently related to the orientation of H-bonds. This results in an anisotropic deformation of the unit cell and an increase of the a parameter in the HP phase at 4.9 GPa, as well as a decrease of linear compressibility along a upon the further compression up to 6 GPa (β_a:β_b:β_c = 5:9:10).