The island of Holsnøy, just to the north of the city of Bergen, is dominated by granulite facies Svecconorwegian (ca 1000 Ma) anorthosites. This area is a focus of research as the granulite facies rocks have been overprinted by eclogite facies assemblages that seem to be related to deformation and the development of both pseudotachylites and shear zones. This overprinting is inferred to have occurred during the Caledonian orogeny at ca 450 Ma when these rocks were subducted below Laurentia. These rocks have been long studied by Håkon Austrheim and his colleagues and the results of their work have been applied to how the lower crust behaves when it is infiltrated by fluids.
More recently our group has been funded by the Australian Research Council to look at this system with a view to applying our findings to aid in the interpretation of geophysical imagery of the lower crust in an Australian setting. Sometimes we have to go to where the rocks are exposed (wherever that is globally) to understand the rock systems that are beneath our feet in Australia.
Well developed eclogite Granulite raft surrounded by eclogite Coronitic anorthosite Lenses of granuliute wrapped by eclogite facies shear zones Pseudotachylite cutting the granulite fabric Eclogite shear zone Two zones of eclogitisation one associated with shearing and one with a fracture Lense of granulite within well-developed eclogite Eclogite shear zone Typical pavement of granulite and eclogite on Holsnøy Pseudotachylite in granulite Conversion of granulite to eclogite along a fracture
Relevant Publications
Phase equilibria modelling constraints on P–T conditions during fluid catalysed conversion of granulite to eclogite in the Bergen Arcs, Norway by Bhowany et al., 2017 in Journal of Metamorphic Geology