INSIGHTS INTO SUBDUCTION ZONE FLUID CHEMISTRIES FROM FLUID INCLUSIONS IN BLUESCHIST FROM SIFNOS, GREECE
Previous petrological and geochronological work on Sifnos and surrounding Aegean islands has provided insight into the metamorphic history of the Hellenic subduction zone, but temporal and compositional constraints on syn-subduction fluids are currently limited. This study thus focuses on two blueschist samples from Sifnos, Greece. The majority of the primary fluid inclusions examined are hosted in epidote, which mineral textures and thermodynamic modeling suggest is a relatively late-stage, retrograde phase. The fluid inclusions are thus interpreted to record high-pressure metamorphic fluids trapped during early stages of exhumation. Additionally, secondary, quartz-hosted inclusions containing halite daughter crystals are present. The halite crystals indicate that the initial fluid was a high salinity brine, containing at least 30 wt% NaCl equivalent. Raman spectroscopy and microthermometry provides information to constrain the P-T conditions of fluid trapping. Combining fluid inclusion data with thermodynamic modeling of major phase stability provides a more complete understanding of the P-T-t history of the system. By building models that predict the stable mineralogy along a subduction and exhumation path, and coupling these models with constructed isochores, inferences can be made about fluid origin, trapping location, and the chemical evolution of fluids through time.