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 C0,-rich fluids has been invoked to account for mid-to upper amphibolite facies (M2,) 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-M2, fluids in the deepest exposed levels of the metamorphic complex. The results indicate that peak-M2, fluids were spatially and compositionally heterogeneous throughout the high-grade core of the complex, whereas post-peak-M2, fluids were generally water-rich. The observed heterogeneities in syn-M2, fluid composition are inconsistent with pervasive C0,-flushing models invoked by previous workers on the basis of fluid inclusion evidence. It is likely that few C0,-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 C0,-rich fluid inclusions in granulite facies rocks.

Fluid record of rock exhumation across the brittle–ductile transition during formation of a Metamorphic Core Complex (Naxos Island, Cyclades, Greece)

“…, 1976; Baker et al. , 1989; Buick & Holland, 1991). Such metamorphic and igneous dewatering are important sources of fluid and dissolved quartz (Connolly, 1997; Thompson, 1997; Sibson & Scott, 1998).…”

“…Such metamorphic and igneous dewatering are important sources of fluid and dissolved quartz (Connolly, 1997; Thompson, 1997; Sibson & Scott, 1998). Petrographic evidence with respect to metamorphic reactions indicates water infiltration into marbles within the migmatite core under both prograde and retrograde metamorphic conditions (Buick & Holland, 1991). Infiltration of water‐rich fluids into the marbles from dehydrating metapelites has also been supported by stable isotope studies on schists and marbles from the middle unit mantling the core of the dome (Baker et al.…”

CO 2 flow during orogenic gravitational collapse: Syntectonic decarbonation and fluid mixing at the ductile-brittle transition (Lavrion, Greece)

“…In this context, increase in temperature leads to partial melting of the orogenic root as attested by numerous Miocene plutons (Keay et al, 2001;Iglseder et al, 2009;Liati et al, 2009;Bolhar et al, 2010) and by the Naxos and Paros migmatite domes exhumed in the central part of the Attico-Cycladic Metamorphic Complex, ACMC in a context of gravitational collapse ( Fig.1a) (Vanderhaeghe and Teyssier, 2001;Vanderhaeghe, 2004;Duchêne et al, 2006;Kruckenberg et al, 2011). CO 2 -rich fluid inclusions in quartz segregations and pegmatites in Naxos Island testify for large fluid production during high grade conditions (Rye et al, 1976;Schuiling and Kreulen, 1979;Kreulen, 1980Kreulen, , 1988Baker et al, 1989;Buick and Holland, 1991;Siebenaller et al, 2013).…”

Ductile shearing, hydrous fluid channelling and high-pressure metamorphism along the basement-cover contact on Sikinos, Cyclades, Greece

“…Franz et al 1993). On Naxos, the situation is complicated by a late high temperature (amphibolite facies) overprint in the basement that has resulted in migmatization (Jansen & Schuiling 1976;Buick & Holland 1991), and has consequently erased all traces of any earlier high pressure mineralogy. In contrast, the basementcover contact is well-exposed on Ios, but its nature remains controversial.…”