305-2 Insights into the Effects of Deep Underplating on the Subduction Interface from the Exhumed Attic Cycladic Crystalline Complex, Greece.

Session: Subduction Zone Processes: Insights from Geology, Geochemistry, and Petrochronology (Posters)

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Abstract:

Exhumed high-pressure metamorphic rocks formed within subduction zones allow for the investigation of rocks brought to depths of 50-60 km within Earth’s mantle and the structural and petrological processes governing the mechanics and dynamics of the subduction channel. While subduction zones are well-studied through geophysical data and modeling, the rock record provides insights into the evolution of the subduction interface that cannot be determined without a physical record. This includes the impact of the inherited structure of the incoming lower plate prior to subduction and the structural evolution of metamorphic rocks during early subduction, deep subduction, and exhumation. 

The Attic Cycladic Crystalline Complex (ACCC, Aegean Sea, Greece), which was exhumed in the back-arc of the Hellenic Subduction Zone, is a premier natural laboratory to study the structural and metamorphic evolution of the deep subduction channel The islands of Evia, Andros, and Tinos in the Cyclades, are characterized by the Cycladic Blueschist Unit (CBU) and preserve the tectonostratigraphic sequence of the uppermost subducting plate. This allows for structural reconstructions of the subduction interface. On these islands, the CBU has been structurally stacked into a series of underplated slices that were formed during subduction and later exhumed and attenuated during extension accommodated by the North Cycladic Detachment System (NCDS). 

This study investigated the impact of the original stratigraphic sequence and the depths and metamorphic conditions of underplating on duplexing and underplating geometries. This work was completed using a combination of field and micro-structural analysis, integrated with U-Pb geochronology. These data were used to determine the original depositional history and resulting mechanical stratigraphy, the current structural arrangement, and the deformation experienced by each underplated slice within the CBU on the three islands. U-Pb age results show an increased number of stratigraphic units in Tinos, where there is increased underplating present, and fewer stratigraphic units in Evia, where there is less underplating and structural relationships between the mapped units. This implies that original stratigraphy has an impact on the current structural relationships and frequency of underplating within the CBU.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9997

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