Fluid release during eclogite formation, North Qaidam Terrane, Western China
Fluids in subduction zones enhance element mobility and reaction kinetics and play important roles in arc magmatism, seismicity, and element recycling into the mantle (Austrheim, 1987; Tsujimori et al., 2006; Bebout, 2007), but observational constraints for fluid processes are scarce. Ultrahigh-pressure (UHP, depths ≥100 km) metamorphic rocks preserve a record of fluid in subduction zones and therefore can help close the data gap (Hermann et al., 2013). I propose to use thermodynamic models to determine the fluid release history and pressure-temperature (PT) path of eclogite samples from the Dulan area, North Qaidam terrane. I will combine these results with existing zircon U-Pb ages to link PT with time (t) and calculate rates of PT and fluid content changes; lawsonite pseudomorphs (Fig. 1) provide evidence of fluid release in these samples. Using rare earth element analysis (REE) to link zircon growth to PT + fluid history will also allow me to test the hypothesis that zircon grew during periods of enhanced fluid release.
Full Thesis Proposal (PDF format)