Modern techniques of stable isotope analysis produce routine high precision analysis of bulk samples, but few studies have successfully determined isotopic ratios with spatial resolution below 5000 pm for silicates or 500 pm for carbonates. Recent developments in laser and ion microprobe techniques allow analysis at the scale of 0.1-50 pm (+ 1 %) and refinements hold promise of precision of + 0.2%. Theoretical considerations and preliminary analytical results predict that sub-millimeter isotopic zonation will be found in many rocks and that analysis of zoning patterns will provide important new evidence regarding fluid migration, recrystallization and diffusion. I propose to use laser microprobe and ion microprobe techniques to study micron-scale zoning in high grade metamorphic rocks. The recently completed (Aug, 1988) laser microprobe system at the University of Wisconsin will provide relatively rapid analysis of samples for O, C, and S isotope ratio at 30-50 pm spatial resolution. I propose to spend my sabbatical (1989-90) using the newly installed (Jan, 1988) Cameca ims/4f ion microprobe at the University of Edinburgh for detailed oxygen and carbon analysis at 0.1-1.0 pm resolution. The principal rocks and to elucidate the causes of such heterogeneity. Samples have been chosen so as to restrict theories of fluid migration in the deep crust, granulite genesis, and cooling/uplift rates.
