| Evidence for metamorphic fluids is abundant in subduction zones, yet the nature of fluid flow in these settings is not well constrained. The goal of this study is to characterize fluid flow processes in three paleo-subduction zones using field and analytical techniques that take advantage of the different scales of fluid-rock interactions preserved in each setting. The three regions studied are New Zealand, Scotland, and Greece. Chemical, isotopic, and mineralogical changes preserved adjacent to fluid conduits at each field site are investigated to develop models for fluid flow at various levels within subduction zones and evaluate the role that fluids play in the long-term geochemical evolution of the continents.; Chemical mass-balance analysis in the New Zealand accretionary prism reveals that dehydration of altered oceanic crust subducting beneath the prism is the most likely source for fluids that deposited quartz veins in the prism. SiO2 transfer from subducting slabs into accretionary prisms may result in the long-term, bulk-silica enrichment of the continents. At similar depths of subduction in Barrow's garnet zone in Scotland, sub-micron-scale isotopic alteration of zircons by fluids yields a precise age for the timing of fluid infiltration and indicates that syn-metamorphic fluid flow caused the growth and/or recrystallization of zircon along grain surfaces and fractures.; Mapping of mineral assemblage distributions in retrograded high pressure, low temperature (HP-LT) metamorphic rocks from Tinos, Greece, reveals that fluids were channelized into lithologic contacts during exhumation and suggests a significant component of slab-parallel flow within the subduction zone preserved on Tinos. From a similar, but relatively unretrograded suite of HP-LT rocks from Syros, Greece, chemical interactions between fluids within a mafic-ultramafic melange zone and adjacent metasedimentary rocks indicate that melange-equilibrated fluids can extract K, Ba, Rb, Cs, Ca, Sr, U, and Pb from metasediments without the need for sediment melting. These elements are typically enriched in arc magmas, strongly suggesting that fluidmetasediment interactions near the slab-mantle interface may be responsible for the U/Th disequilibrium and elevated K/Th, U/Th, Ba/Th, and Sr/Th ratios that are diagnostic of are magmatism. |
