Metastability and HP metamorphism at fluid deficient conditions, an example from the Bergen Arcs (Western Norway)

Abstract

In the Lindæs Nappe, Bergen Arcs Western Norway, Precambrian granulites facies anorthosites (P<10 kbars, T=800°C) and their Caledonian eclogite (P<17 kbars, T=700°C) and amphibolite facies equivalents alternate on meter scale. It has recently been suggested by Camacho et al. (2005) that the granulite facies anorthosites, remained at low temperatures (350°C) and were only locally heated to 700°C and reacted to eclogites by spasmodic hot fluids. This is in contrast to previously published models (Austrheim 1987) where the fluid-triggered mineral reactions in a terrain that was at 700°C during the Caledonian Orogeny. In the latter model the dry granulites metastably survive the Caledonian HP/HT metamorphic event at 425 Ma...