The early P-T evolution of a garnet-kyanite gneiss from the Variscan Ulten Zone has been defined by detailed petrographic observations leading to the detection of chlorite-epidote- and staurolite-bearing assemblages enclosed in kyanite porphyroblasts. Calculations of P-T pseudosections in the system NaCaKFeMgAlSiHO allowed us to constrain the evolution for these relics from the earliest metamorphic stages. The overall path shows a P-T increase to a peak of 11-12 kbar and 600-650ºC followed by decompressional heating to 720ºC and 9-10 kbar and final cooling at 7 kbar, 550-600ºC. This clockwise P-T path reflects crustal thickening and subsequent thermal decay related to the continental collision of the Variscan orogeny 330-340 Ma ago. Our study demonstrates that large kyanite porphyroblasts may preserve assemblages related to prograde metamorphic stages. As a result, the detection of mineral inclusions in kyanite can complement many similar studies on mineral suites hosted in garnet and zircon.

An early metamorphic stage for the Variscan Ulten Zone gneiss (NE Italy): evidence from mineral inclusions in kyanite.

BRAGA, ROBERTO;MORTEN, LAURO
2007

Abstract

The early P-T evolution of a garnet-kyanite gneiss from the Variscan Ulten Zone has been defined by detailed petrographic observations leading to the detection of chlorite-epidote- and staurolite-bearing assemblages enclosed in kyanite porphyroblasts. Calculations of P-T pseudosections in the system NaCaKFeMgAlSiHO allowed us to constrain the evolution for these relics from the earliest metamorphic stages. The overall path shows a P-T increase to a peak of 11-12 kbar and 600-650ºC followed by decompressional heating to 720ºC and 9-10 kbar and final cooling at 7 kbar, 550-600ºC. This clockwise P-T path reflects crustal thickening and subsequent thermal decay related to the continental collision of the Variscan orogeny 330-340 Ma ago. Our study demonstrates that large kyanite porphyroblasts may preserve assemblages related to prograde metamorphic stages. As a result, the detection of mineral inclusions in kyanite can complement many similar studies on mineral suites hosted in garnet and zircon.
2007
Braga R.; Massonne H.-J.; Morten L.
File in questo prodotto:
Eventuali allegati, non sono esposti

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/61514
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 26
  • ???jsp.display-item.citation.isi??? 25
social impact