High pressure-low temperature metamorphism in the Gran Paradiso basement, Western Alps

Autor: J. R. Vearncombe
Rok vydání: 1983
Předmět:
Zdroj: Journal of Metamorphic Geology. 1:103-115
ISSN: 1525-1314
0263-4929
DOI: 10.1111/j.1525-1314.1983.tb00267.x
Popis: The Gran Paradiso basement complex of the French and Italian Alps is composed of metasediments, termed the gneiss minuti, and metabasic rocks, both of which are intruded by a late Hercynian granite. The Bonneval gneiss, which crops out at the western edge of the complex, is composed of highly deformed metasediments, volcanics and volcaniclastic rocks. Eclogites, now highly altered, occur in the metabasic rocks. Kyanite and blue-green amphibole are locally present in the gneiss minuti and aegirine plus riebeckite occur in the Bonneval gneiss. A moderately high pressure - low temperature metamorphic event of probable Alpine age occurred in the basement complex. This metamorphic event differs from that in the overlying Sesia unit and ophiolites of the Schistes lustres nappe in being at lower pressures (below the ab = jd100+ qz transition) and post-dating the major (D2A) deformation. The origin of the metamorphism is discussed and interpreted as a probable consequence of the overlying nappe pile which was emplaced during the D2A event. Subsequent greenschist facies metamorphism in the basement complex is a consequence of thermal relaxation during uplift.
Databáze: OpenAIRE
Externí odkaz: