Geochemical and stable isotope resetting in shear zones from Täschalp: constraints on fluid flow during exhumation in the Western Alps

摘要: Fluid flow at greenschist facies conditions during exhumation of the western Alps occurred in several penecontemporaneous systems, including shear zones lithological contacts, deformed contacts between serpentinite bodies and metabasalts, albite veins within calcite + quartz calcareous schists. that juxtapose metasediments ophiolitic rocks Piemonte Unit reset O H isotope ratios. δ18O values are buffered by wall rocks; however, calculated fluid δ2H similar all suggesting they formed an interconnected network. The similarity sheared those unsheared schists suggests fluids were derived from, or had equilibrated with, envelop ophiolite rocks. Time-integrated fluxes estimated from changes Si metabasalts up to 105 m3 m−2, with flowing temperature driven either topography seismic pumping. Individual active for c. 2–3 Myr, implying average 10−9 m3 m−2 s−1. Rocks away show much less marked isotopic geochemical changes, volumes decreased into unit, consistent source being metasediments. Fluids generated dehydration reactions intersected and, while many affects fluid–rock interaction, large-scale major units was not common.