Lower plate serpentinite diapirism in the Calabrian Arc subduction complex

Area of Science:

• Geology
• Geophysics
• Tectonics

Background:

• Mantle-derived serpentinites are typically found at magma-poor rifted margins and above subduction zones.
• Their formation is usually attributed to fluids released from the subducting slab to the mantle wedge.

Purpose of the Study:

• To present evidence for a novel class of serpentinite diapirs within the Calabrian Arc's external subduction system.
• To investigate the origin and emplacement mechanisms of these serpentinites, distinguishing them from typical subduction-related serpentinization.

Main Methods:

• Geological mapping and structural analysis of the Calabrian Arc.
• Seismic data interpretation to identify diapiric structures and associated faults.
• Geochemical analysis of serpentinite samples to determine origin and alteration history.

Main Results:

• Identification of serpentinite diapirs originating directly from the lower plate, not the mantle wedge.
• Serpentinite emplacement is linked to lithospheric faulting associated with incipient rifting and accretionary wedge collapse.
• Mantle-derived diapirism in this context is decoupled from active subduction processes.

Conclusions:

• The studied serpentinites likely formed during Mesozoic Tethyan rifting and were transported beneath the subduction system via plate convergence.
• Inherited lower plate serpentinites ascend through lithospheric faults that segment the margin.
• The co-occurrence of seismogenic features and these deep-seated serpentinite diapirs constrains the mechanisms for exposing altered mantle peridotite at the seafloor long after its initial formation.