Original paper
Mullite-Sillimanite lntergrowth from Pelitic Inclusions in Bergell Tonalite
Wenk, H.-R.
Neues Jahrbuch für Mineralogie - Abhandlungen Band 146 Heft 1 (1983), p. 1 - 14
19 references
published: Mar 10, 1983
ArtNo. ESP154014601000, Price: 29.00 €
Abstract
Submicroscopic mullite (a = 14.9 Å, b = 7.6 Å, c = 5.7 Å) has been found as domains in sillimanite in pelitic inclusions in Bergell tonalite from Vai Sissone (N. Italy). It shows an APB structure, probably with R =1/2 a zigzaging parallel to [210]. Sillimanite contains R = 1/2c APB’s which are due to Al-Si ordering. They are preferentially aligned parallel to (010) thus avoiding Al-O-Al bonds. A structural model is proposed for this mullite showing the probable formation by ordering and exsolution of an originally disordered nonstoichiometric aluminosilicate. Some microstructural observations on other aluminosilicates from the Bergell Alps are added. High dislocation densities are observed in fibrolite, predominantly of screw character with a Burgers vector b = [001].
Keywords
Mullite • sillimanite • intergrowth • alumosilicate • exsolution • order-disorder • antiphase boundaries • TEM data • inclusion • tonalite • Trentino-Alto Adige • Bergell Massif (Vai Sissone)