On pressure-temperature-time paths of crustal metamorphism

Metamorphic P-T-t paths, which delineate the evolution of pressure (P)-temperature (T) conditions through time (t) for crustal rocks during tectonic evolution, have become a pivotal link connecting metamorphism, orogenic evolution, and geodynamic processes. This paper traces the development of metamorphic P-T-t path research, focusing on six landmark publications that illustrate its progression from conceptual origins and model development to methodological implementation, and finally to precise spatiotemporal reconstruction through integration with geochronology. Together, these studies have driven the transformation of metamorphic petrology from static description to the study of dynamic evolution, thereby altering our understanding and approach to investigating orogenic belts. While inevitably constrained by the scientific and technical contexts of their time, these classic studies exhibit certain limitations in aspects such as fluid behavior, diffusion re-equilibration, mineral disequilibrium, and multi-scale coupling. Nevertheless, they have provided a clear direction for the subsequent development of metamorphic studies, such as high-temperature and high-pressure experiments, in-situ microanalysis, and numerical modeling. Probably, P-T-t studies will be further integrated with other disciplines, playing a crucial role in fields such as extreme metamorphic processes and the tectonic evolution of the early Earth.