Calcite marbles as records of episodic deformation during exhumation of high-pressure rocks (Syros Island, Aegean region)

This is supplementary material for the manuscript submitted to Tectonics titled "Calcite marbles as records of episodic deformation during exhumation of high-pressure rocks (Syros Island, Aegean region)".We present new calcite microstructural, petrofabric, and grain size data from high-pressure marbles, integrated with microstructural observations from associated greenschists, to investigate spatio-temporal variations in deformation intensity during the exhumation of the Cycladic Blueschist Unit in southern Syros Island (Cycladic Massif, Aegean region). Our results reveal a pronounced spatial and temporal heterogeneity in deformation intensity across different structural levels and metamorphic conditions. Intense deformation occurred under eclogite- to early blueschist-facies conditions was followed by a period of deformation cessation, marked by the widespread development of columnar aragonite microstructure, indicative of static conditions. Deformation resumed during continued exhumation at lower-pressure blueschist-facies conditions, becoming increasingly localized in the lower structural levels, where the columnar fabric underwent dynamic recrystallization, while the upper levels remained undeformed. At greenschist-facies conditions, deformation ceased and was restricted to narrow, foliation-parallel bands, with no direct link to major tectonic structures. Our results suggest an early exhumation characterized by intense top-to-SE deformation, possibly related to internal imbrication of the rock pile. Subsequently, rocks were exhumed as a coherent body via a top-to-NE extrusion mechanism that operated from blueschist- to greenschist-facies conditions with the deformation becoming progressively localized along the bounding faults of the wedge. High-pressure marbles provide robust markers of deformation heterogeneity and play a critical role in distinguishing discrete deformation phases from eclogite- to greenschist-facies conditions. Our findings underscore the value of integrating calcite microstructures with mineral and structural data to resolve the complex deformation histories associated with the exhumation of high-pressure rocks.