Tectonics of the Isua Supracrustal Belt 1: P?T?X?d Constraints of a Poly?Metamorphic Terrane

The Eoarchean Isua supracrustal belt (ISB) has been interpreted as one of the earliest records subduction processes, leading to conclusion that a plate tectonic geodynamic system was likely operating since early Archean. However, proposed models remain difficult evaluate our understanding metamorphic and structural evolution remains fragmentary. Here, we present study rocks ISB. We used petrographic microstructural observations, phase equilibria, isopleth geothermobarometry, conventional thermometry explore prograde, peak, retrograde northeastern Our results show ISB syn-tectonic, amphibolite facies event (M1) with peak conditions 550°C–600°C 0.5–0.7 GPa. M1 followed by static, lower (M2; <540°C <0.5 GPa). Published constraints suggest M2 occurred in late (>3.5 Ga) Neoarchean (<2.9 Ga), respectively. These events are partially overprinted low temperature (<500°C) retrogression (M3) is most intensely developed part belt; it typically overprints some mineral phases while preserving fabric. findings consistent spatially homogeneous syn-tectonic metamorphism macroscale folding. Such features predicted heat-pipe model. Therefore, permit interpretation record nonuniformitarian processes.