Exhumation Mechanisms of High-Pressure Rocks With High-Temperature Overprinting: Insights From Eclogites of the Baie Verte Peninsula, Newfoundland

Abstract

This study presents a comprehensive examination of exceptionally preserved eclogites from the Baie Verte Peninsula, Newfoundland Appalachians, which display a high-temperature overprint, thus offering insights into the metamorphic evolution and exhumation mechanisms of such terrains. Through an integrated approach combining field observations, petrographic analysis and thermodynamic modelling, we unravel the tectonometamorphic history of the Taconic eclogites within the East Pond Metamorphic Suite. The eclogites record a complex multistage metamorphic path characterized by initial A-subduction at ~2.7 GPa at ~640°C, followed by near-isothermal decompression to ~2 GPa at ~660°C, and significant heating during exhumation to the metamorphic peak (~1.5 GPa, ~800°C). We highlight the pivotal role of fluids in facilitating metamorphic reactions and influencing the rheology and buoyancy of subducting slabs. We propose a two-stage exhumation model for these eclogites: (1) initial ascent driven by buoyancy forces within a low-density and low-viscosity mantle wedge and (2) subsequent exhumation to shallower crustal levels, aided by external tectonic forces, such as shear zone displacement, erosion or extension. The relationship between the hydration history and the reconstructed pressure–temperature path, featuring a β-shaped trajectory, underscores the significance of thermal perturbations and fluid migration in the exhumation history of HP–UHP terrains in subduction–collision zones.