Advantages and Limitations of Combined Diffusion-Phase Equilibrium Modelling for Pressure–Temperature–Time History of Metamorphic Rocks

ABSTRACT This paper presents and discusses the results of phase diagram (Perple_X) diffusion modelling (CZGM, or Compositional Zoning its Modification by diffusion) to constrain P–T path metamorphism. The approach is based on best fits between zoning profile in measured garnet that obtained intersections isopleths calculated using whole rock bulk composition. model was applied garnets natural rocks various metamorphic grades, which were formed within different geotectonic environments. To compare sequence compositional change during Barrovian-type metamorphism, well-studied pelitic from garnet–staurolite, kyanite–sillimanite, sillimanite-K-feldspar zones selected. Garnets with two-stepped core rim profiles two stages events used for pressure–temperature (P–T) constraint each stage event. For high-grade rocks, original severely modified, initial quantified estimate timescale These include high- ultra-high-pressure subjected thermal overprinting collisional orogenesis. application this allow deciphering reason why does not fit low-grade has preserved zoning. includes whose nucleation shifted garnet-in boundary higher temperatures pressures, as well crystallised events. Finally, paths constrained after multicomponent quantified, further P–T-time metamorphism rocks.