The nature and distribution of fluids during amphibolite facies metamorphism, Naxos (Greece)

Abstract

On the basis of fluid inclusion evidence, pervasive influx of deep‐seated CO2‐rich fluids has been invoked to account for mid‐ to upper amphibolite facies (M2B) metamorphism on the island of Naxos (Cyclades, Greece). In this paper, mineral devolatilization and melt equilibria are used to constrain the composition of both syn‐ and post‐peak‐M2B fluids in the deepest exposed levels of the metamorphic complex. The results indicate that peak‐M2B fluids were spatially and compositionally heterogeneous throughout the high‐grade core of the complex, whereas post‐peak‐M2B fluids were generally water‐rich. The observed heterogeneities in syn‐M2B fluid composition are inconsistent with pervasive CO2‐flushing models invoked by previous workers on the basis of fluid inclusion evidence. It is likely that few CO2‐rich fluid inclusions on Naxos preserve fluids trapped under peak metamorphic conditions. It is suggested that many of these inclusions have behaved as chemically open systems during the intense deformation that accompanied the uplift of the metamorphic complex. A similar process may explain the occurrence of some CO2‐rich fluid inclusions in granulite facies rocks.