Studi sperimentali sui pirosseni onfacitici: sintesi idrotermali a moderate pressioni. Parte II. Soluzioni solide $CaMgSi_{2}O_{6} \rightleftharpoons ^ Na(Al,Fe^{3+})Si_{2}O_{6}$

Bondi, Mirella ; Morten, Lauro ; Mottana, Annibale

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 71 (1981) no. 6, pp. 191-202

Résumé

Experimental studies have been carried out along the diopside-jadeite join and along ternar13y compositions diopside-jadeite with 10 mol % acmite added, using coprecipitated gels as starting materials. Pressures between 1 and 30 kbar $P(H_{2}O)$ at temperatures 450 to 1200 °C were used. The solid solution limit between Di and Jd is $13 \pm 1$ mol % for pressures 1, 2 an d 3 kbar $P(H_{2}O)$. The ternary compositions vary widely in their cell parameters as a consequence of experimental difficulties encountered in sealing the capsules to outside components (oxygen mainly), as well as a result of the fact that starting materials were mixes of diopsidic pyroxene and jadeitic/acmitic glasses, the production of homogeneous gels having proved to be impossible. The synthesis of stoichiometric chloromelanite $(Di_{33}Jd_{33}Ac_{33})$ did not succeed for the same reason, in spite of the use of solid-state buffers.