Deformation-induced, retrograde transformation of kyanite to andalusite: An example of felsic granulite in the southern Bohemian Massif

0584749 - GLÚ 2025 RIV NL eng J - Článek v odborném periodiku
Yoshioka, T. - Kanagawa, K. - Hiroi, Y. - Hirajima, T. - Svojtka, Martin - Hokada, T. - Wallis, S. R. - Nagaya, T. - Miyake, C.
Deformation-induced, retrograde transformation of kyanite to andalusite: An example of felsic granulite in the southern Bohemian Massif.
Tectonophysics. Roč. 877, April (2024), č. článku 230293. ISSN 0040-1951. E-ISSN 1879-3266
Institucionální podpora: RVO:67985831
Klíčová slova: Kyanite * Andalusite * Phase transformation * Ductile shear zone * Felsic granulite * Southern Bohemian Massif
Obor OECD: Mineralogy
Impakt faktor: 2.9, rok: 2022
Způsob publikování: Open access
https://www.sciencedirect.com/science/article/pii/S0040195124000957?via%3Dihub

Detailed microstructural, microfabric and chemical analyses of felsic granulite within and around a ductile shear zone at the Plešovice quarry in the southern Bohemian Massif revealed deformation-induced, retrograde transformation of kyanite to andalusite. Although andalusite is absent outside the shear zone, its fraction among Al₂SiO₅ polymorphs significantly increases up to ~59% inside the shear zone, while the fraction of kyanite significantly decreases from ~98% outside the shear zone down to ~22% inside the shear zone. Three examples of andalusite and the relict kyanite pair suggest a common topotaxial relationship such that andalusite (010) is parallel to the precursory kyanite (100), while andalusite [100] and [001] are parallel to the precursory kyanite [010] and [001], respectively, indicating that the growth of andalusite was crystallographically controlled by the precursory kyanite. The felsic granulite in the ductile shear zone at the Plešovice quarry has been repeatedly subjected to brittle shearing accompanied by pseudotachylite formation and plastic shearing with mylonitization, suggesting development of the ductile shear zone at the brittle–plastic transition zone. Mylonitization of the felsic granulite was promoted by deformation-induced K-feldspar replacement by myrmekite at temperatures of 390–440 ◦C assuming a pressure of 250 MPa.
Trvalý link: https://hdl.handle.net/11104/0352610