title: Field measurement of slow metamorphic reaction rates at temperatures of 500 degrees to 600 degrees C
abstract: High-temperature metamorphic reaction rates were measured using strontium isotopic ratios of garnet and whole rock from a field site near Simplon Pass, Switzerland. For metamorphic conditions of cooling from 612 degrees +/- 17 degrees C to 505 degrees +/- 15 degrees C at pressures up to 9.1 kilobars, the inferred bulk fluid-rock exchange rate is 1.3(-0.4)(+1.1) x 10(-7) grams of solid reacted per gram of solid per year, several orders of magnitude lower than laboratory-based estimates. The inferred reaction rate suggests that mineral chemistry may lag the evolving conditions in Earth's crust during mountain building.
authors.affiliation: Department of Geology and Geophysics, University of California, 301 McCone Hall, Berkeley, CA 94720, USA.
authors.initials: EF
authors.lastname: Baxter
authors.initials: DJ
authors.lastname: DePaolo