Tectonic Processes in Accreted Terranes

Accreted terranes are distinct fragments of crust—often island arcs, oceanic plateaus or microcontinents—that become welded onto the margins of larger continental blocks through subduction and collision. As oceanic lithosphere descends, buoyant fragments resist complete subduction and are scraped off the downgoing slab, forming accretionary prisms. Continued convergence drives underplating of these terranes beneath the forearc, localised metamorphism and crustal thickening. Strike-slip faults and translational shearing may then dismember once coherent terrane assemblages, imparting kilometric displacement and complex geometries. Subsequent exhumation exposes high-pressure metamorphic rocks and thrust slices, offering a window into deep crustal processes. Across the Pacific margin of North America, for example, multiple terranes have successively accreted since the Mesozoic, generating orogenic belts rich in mineral deposits, seismic hazards and topographic relief. Modern seismic tomography and thermochronology elucidate slab geometry and the timing of terrane burial and uplift, while structural mapping reveals discrete sutures and fault-bounded slices. Understanding these processes is essential both for reconstructing past plate motions and for assessing the distribution of geothermal resources, metallogenesis and earthquake risk along active continental margins.

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Tectonic Processes in Accreted Terranes publication trend

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Technical terms

Accreted terrane: A crustal fragment—such as an island arc or microcontinent—that has been tectonically joined to a continental margin.

Subducted slab: The portion of oceanic lithosphere that sinks into the mantle at convergent plate boundaries.

Suture zone: A structural boundary marking the collision and welding of two distinct crustal blocks.

Underplating: The emplacement of material—sedimentary, volcanic or metamorphic—beneath the overriding plate at a convergent margin.

Exhumation: The process by which deep-seated rocks are returned to shallower crustal levels through uplift and erosion.

References

1. Mantle and geological evidence for a Late Jurassic–Cretaceous suture spanning North America. Geological Society of America Bulletin (2017).
2. Raising the Resurrection plate from an unfolded-slab plate tectonic reconstruction of northwestern North America since early Cenozoic time. Geological Society of America Bulletin (2020).
3. Tectonic Underplating and Dismemberment of the Maclaren‐Kluane Schist Records Late Cretaceous Terrane Accretion Polarity and ~480 km of Post‐52 Ma Dextral Displacement on the Denali Fault. Tectonics (2021).