The life cycle of subcontinental peridotites: From rifted continental margins to mountains via subduction processes

Abstract

Serpentinization greatly affects the physical and chemical properties of lithospheric mantle. Here we address the fate of serpentinized peridotites and their influence over an entire Wilson cycle. We document the near-surface journey of serpentinized subcontinental peridotites exhumed during rifting and continental breakup, reactivated as buoyant material during subduction, and ultimately emplaced as “ophiolite-like” fragments within orogenic belts. This life cycle is particularly well documented in former Tethys margins, where recent studies describe the ongoing incorporation of Mesozoic serpentinized subcontinental peridotites that diapirically rise from a subducting lower plate’s mantle to be emplaced into the accretionary prism in front of a continental arc. This newly recognized mode of subduction-linked serpentine diapirism from the downgoing lithospheric slab is consistent with the origin of some exhumed serpentinized subcontinental peridotites in the Apennines (Italy), these assemblages reaching their present locations during Alpine orogenesis. Transfer of serpentinized subcontinental peridotites from the downgoing to the overriding plate motivates the concept of a potentially “leaky” subduction channel. Weak serpentine bodies may in fact rise into, preferentially migrate within, and eventually leave the intraplate shear zone, leading to strong lateral heterogeneities in its composition and mechanical strength.

The lifecycle of sub-continental peridotites: From rifted continental margins to mountains via subduction processes: REPLY

“…In figure 4b, below the topmost ~4 km of crystalline basement, the green profiles have seismic velocities midway between continental and oceanic crust. The brown profiles at the northern end of the seismic line are compatible with either oceanic crust or more heavily serpentinized peridotites than those inferred at analogous depths in the Tyrrhenian, for example those linked to continental rifting in western Iberia (Vannucchi et al, 2020).…”

Modification of Lithospheric Mantle by Melts/Fluids With Different Sulfur Fugacities During the Wilson Cycle: Insights From Lesvos and Global Ophiolitic Peridotites

“…As remnants of past oceanic lithosphere, ophiolites could potentially record the life cycles of ocean basins from their rift‐drift and seafloor spreading to subduction initiation and terminal closure (Dilek & Furnes, 2011, 2014; Xu et al., 2020; Vannucchi et al., 2020). Different types of ophiolites formed in various tectonic environments, such as ocean‐continent‐transition (OCT), mid‐ocean‐ridges (MOR), and supra‐subduction‐zone settings (SSZ; Dilek & Furnes, 2014 and references therein), are believed to represent different phases of the Wilson Cycle (Burke, 2011; Wilson, 1968).…”