Lower plate serpentinite diapirism in the Calabrian Arc subduction complex

A Polonia,M Schmidt,M Carlini,E Bonatti,S Romano,F Muccini,L Gasperini,A Artoni,C Hensen,L Torelli,L Cocchi

doi:10.1038/s41467-017-02273-x

Abstract

Mantle-derived serpentinites have been detected at magma-poor rifted margins and above subduction zones, where they are usually produced by fluids released from the slab to the mantle wedge. Here we show evidence of a new class of serpentinite diapirs within the external subduction system of the Calabrian Arc, derived directly from the lower plate. Mantle serpentinites rise through lithospheric faults caused by incipient rifting and the collapse of the accretionary wedge. Mantle-derived diapirism is not linked directly to subduction processes. The serpentinites, formed probably during Mesozoic Tethyan rifting, were carried below the subduction system by plate convergence; lithospheric faults driving margin segmentation act as windows through which inherited serpentinites rise to the sub-seafloor. The discovery of deep-seated seismogenic features coupled with inherited lower plate serpentinite diapirs, provides constraints on mechanisms exposing altered products of mantle peridotite at the seafloor long time after their formation.

Highlights

Mantle-derived serpentinites have been detected at magma-poor rifted margins and above subduction zones, where they are usually produced by fluids released from the slab to the mantle wedge
Whereas Area-2 and -3 are located north and northeast of Alfeo Seamount; the more distal Area-4 is located on a slope terrace of the accretionary complex
We suggest three possible scenarios for serpentinite emplacement in the Ionian Sea: during Pleistocene shear processes and fluid migration along the Alfeo-Etna fault (AEF); as a consequence of Calabrian Arc (CA) subduction; or during the formation of the Tethyan Ocean

Summary

Introduction

Mantle-derived serpentinites have been detected at magma-poor rifted margins and above subduction zones, where they are usually produced by fluids released from the slab to the mantle wedge. Mechanical/numerical models taking into account geometry and strength contrast across the Neo-Tethyan passive margin and major faults, suggest that pre-existing fracture zones and transform faults controlled the subsequent Ionian margin segmentation[17]. In this context, the NW portion of the IF corresponds to basement deformation associated with slab tearing, whereas the AEF might be the result of regional scale dextral shearing

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Conclusion