Geochemical Zoning in Metamorphic Minerals

Geochemical zoning of major and trace elements, as well as stable and radiogenic isotopes in metamorphic minerals, is reviewed, emphasizing theoretical models of compositional zoning and classic or particularly illustrative examples from the literature. Chemical and isotopic implications of Rayleigh distillation, equilibrium partitioning and growth zoning, diffusion, kinetic limitations within the rock matrix, and dissolution-reprecipitation are explored. Implications for geospeedometry and thermobarometry are also developed. Major elements and stable isotopes commonly conform well to equilibrium models of crystal growth and diffusional reequilibration during cooling, but trace elements and by extension radiogenic isotopes are strongly affected by reactions involving accessory minerals and kinetic limitations.