FLUID-FLOW DURING DEEP CRUSTAL METAMORPHISM, AN INTRODUCTION TO NEW DATA FROM THE SOUTHERN MARGINAL ZONE OF THE LIMPOPO BELT

New data on fluid flow through the Southern Marginal Zone of the Limpopo Belt are in the papers for this volume by Baker et al., Hoerns and Van Reenen, Vennemann and Smith and Van Schalkwyk et al. These data appear to support an hypothesis that a small amount of CO2-rich fluid entered the Southern Marginal Zone at high (but subsolidus) temperatures and participated in retrograde reactions. However, there remain unexplained inconsistencies between conclusions based on the petrologic results and those based on the stable isotopic results. The new data are here reviewed and are considered in the context of contemporary discussions on the origins and roles of fluids in high-grade metamorphism.