Fiamme degassing structures and their implications for the post-emplacement temperatures and H2O contents of high-grade ignimbrites

Abstract

Abstract A new process in post-emplacement ignimbrite degassing is proposed from observations of unusual structures in a high-grade ignimbrite in Sardinia. The structures consist of fiamme decorated above and below by vesicles, termed here Fiamme Degassing Structures (FDS). The relative volumes of vesicles and fiamme have a positive, linear correlation, and the ratio between the volume of vesicles above and below fiamme (asymmetry ratio) is \u202f1\u202fwt% at