Stephen Centrella, 2019. "The granulite- to eclogite- and amphibolite-facies transition: a volume and mass transfer study in the Lindås Nappe, Bergen Arcs, west Norway", Metamorphic Geology: Microscale to Mountain Belts, Silvio Ferrero, Pierre Lanari, Philippe Goncalves, Eugene G. Grosch
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This study is focused on a specific outcrop in the Bergen Arcs, Norway where the transition between dry granulite and the hydrated eclogite and amphibolite is exposed. In this outcrop the foliation in the granulite is continuous as it passes through eclogite- and amphibolite-facies rocks, presenting a challenge to understanding the nature of these spatial relationships. Although there is no major change in the bulk chemical composition of all three metamorphic-facies rocks, the loss of ignition (LOI) content increases from granulite to the eclogite and to the amphibolite. During hydration and metamorphism, the density changes from c. 3 g cm−3 for the anorthositic granulite to 3.2 g cm−3 for the eclogite, and 2.75 g cm−3 for the amphibolite. Based on the mass balance equation, eclogitization of the granulite shows a reduction of volume of c. 3% whereas amphibolitization of the granulite gains c. 5% in volume. By assuming equilibrium, modelling the phase equilibria provides estimates of the amount of fluid necessary to form the eclogite and the amphibolite assemblages. Results show that both assemblages can be stable at similar temperature and a similar fluid composition but differ in pressure by c. 10 kbar. This study suggests that the stress generated during hydration of the granulite may influence the local mineral assemblage equilibrium.
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Metamorphic Geology: Microscale to Mountain Belts
CONTAINS OPEN ACCESS
In Earth evolution, mountain belts are the loci of crustal growth, reworking and recycling. These crustal-scale processes are unravelled through microscale investigations of textures and mineral assemblages of metamorphic rocks. Multiple episodes of metamorphism, re-equilibration and deformation, however, generally produce a complex and tightly interwoven pattern of microstructures and assemblages. Over the last two decades, the combination of advanced computing and technological capabilities with new concepts has provided a vast array of novel petrological tools and high-resolution/high-sensitivity techniques for microanalysis and imaging. Such novel approaches are proving fundamental to untangling the enigma represented by metamorphism with an unprecedented level of detail and confidence. As a result, the first decade and a half of this century has already seen the tumultuous development of new research avenues in metamorphic petrology. This book aims to provide a timely overview of the state of the art of this field, of newly developed petrological techniques, future advancements and significant new case studies.