Pre‐Subduction Architecture Controls Coherent Underplating During Subduction and Exhumation (Nevado‐Filábride Complex, Southern Spain)

Abstract

AbstractThe interplay between structural and metamorphic processes operating along the deep plate interface in subduction zones remains elusive as much of the geologic record is recycled into the mantle. In some cases, metamorphosed subducted rocks are underplated and exhumed to the surface, providing critical constraints on structural processes and the rheological evolution of subduction interfaces at convergent margins. One such exhumed high‐pressure/low‐temperature subduction complex is the Cenozoic Nevado‐Filábride Complex (NFC) in Southern Spain. This study presents new data from the NFC that elucidate the syn‐metamorphic deformation, stacking, and underplating of continental slivers along the subduction interface. The structurally lowest NFC dominantly comprises lithologically monotonous Paleozoic metamorphic basement rocks recorded by apatite U‐Pb ages and shows no evidence for large‐scale internal duplications suggesting it behaved as a coherent basement succession during subduction. In contrast, structurally higher levels of the NFC are characterized by the stacking of older‐on younger coherent slices and distinctly different metamorphic ages. These relationships document syn‐subduction structural repetitions and tectonic stacking of imbricate thin slivers (∼100s m) during subduction underplating. Structurally higher levels of the NFC exhibit both Eocene and Miocene metamorphic zircon rims and apatite ages, along with microstructures indicative of relatively higher temperature metamorphism. Large‐scale underplating and antiformal stacking of slivers in the subduction channel can provide buoyancy forces to underplate and assist exhumation. We demonstrate that the presubduction stratigraphic architecture is a key control on the style and timing of deformation and metamorphism, facilitating coherent subduction underplating.