Dehydration-Induced Supralithostatic Fluid Overpressure in Metapelites from Northern Korea

Abstract

Our understanding of orogenic dynamics largely relies on the lithostatic paradigm, which correlates thermodynamic pressure to burial depths. Deviations from lithostatic conditions often involve fluid overpressure, yet the mechanisms in natural rocks remain elusive. In this study, we integrate petrological analysis, radiometric dating, and diffusion chronology to explore the thermal overprinting on metapelites from a Precambrian orogen caused by ~ 110 Ma andesitic porphyry intrusions in Northern Korea. The metapelites’ mineral assemblages, particularly the dissolution-reprecipitation textures of garnet and monazite, reveal rapid heating, dehydration, and reworking within ~ 300 years, reaching 600‒640°C and 7.5‒8.5 kbar at ~ 110 Ma. The barometric results sharply contrast with the shallow emplacement depths of the andesitic porphyries, indicating supralithostatic fluid overpressure. These findings challenge the lithostatic paradigm and suggest that rapid dehydration and deviation from lithostatic pressures may be more prevalent than previously recognized, with significant implications for orogenic reconstructions and seismogenic behaviors at plate boundaries.