Geodynamics and Tectonic Processes in Zealandia

Zealandia represents a largely submerged continental fragment rifted from East Gondwana during the Cretaceous, with its present morphology controlled by successive phases of extension, magmatic accretion and subduction. Initial rifting between 100 and 80 Ma separated Lord Howe Rise, Chatham Rise and the Hikurangi Plateau from Antarctica and Australia, while intra‐oceanic plateaus and fracture zones shaped the continental margin. Subduction along the paleo‐Pacific boundary drove Mesozoic arc magmatism, crustal thickening, and periodic magmatic flare-ups. In the mid-Cenozoic, shifts in plate motion induced transpressional deformation, mantle flow perturbations and delamination of dense lower crust. These geodynamic events produced uplift and subsidence patterns observed today, influenced seismic and volcanic hazards, and controlled sedimentary basin evolution. Zealandia thus offers a unique natural laboratory for examining processes of continental breakup, arc construction, slab‐mantle interactions and crustal foundering in a submerged continental setting.

Research from Nature Portfolio

Recent studies have reappraised the Mesozoic cordilleran arc that formed along Zealandia’s paleo‐Pacific margin. Geochemical and zircon Hf isotope data reveal two temporally distinct arc components around 130 Ma, marked by a shift from low to high Sr/Y ratios. Reconstructed crustal thickness doubled to ~80 km during a magmatic flare-up, with addition rates rising from ~14 to ~100 km³ my⁻¹ per km of arc, highlighting upper‐plate processes in crustal growth and matching patterns seen in North and South American Cordilleran arcs. Other work has focused on the metamorphic drivers of crustal foundering in southwestern New Zealand. Detailed pressure–temperature modelling of Cretaceous monzodiorite–gabbro plutons demonstrates that efficient eclogite-facies metamorphism and accumulation of garnet–clinopyroxene cumulates (>75 mol %) are prerequisites for density-driven delamination. The preservation of buoyant monzodioritic units emphasises the role of crustal dismemberment and extensional shear-zone development in facilitating the excision and sinking of dense lower crust.

Geodynamics and Tectonic Processes in Zealandia publication trend

The graph below shows the total number of articles in geodynamics and tectonic processes in zealandia across all publications each year (not limited to Nature Index journals).

Technical terms

Subduction: The process by which one tectonic plate sinks beneath another into the mantle at a convergent boundary.

Arc magmatism: Volcanic and plutonic activity above a subducting slab, generating magmas with characteristic trace-element signatures.

Slab rollback: The retreat of a subducting plate hinge, causing extension in the overriding plate and mantle flow changes.

Delamination (foundering): The detachment and sinking of dense lower crust or lithospheric mantle into the mantle due to metamorphic densification.

Lithospheric keel: A thick, compositionally distinct root of ancient (often Precambrian) lithosphere that underlies and stabilises continental fragments.

Eclogite facies: A high-pressure metamorphic condition in which mafic rocks transform into dense garnet–omphacite assemblages, facilitating crustal foundering.

References

1. Cordillera Zealandia: A Mesozoic arc flare-up on the palaeo-Pacific Gondwana Margin. Scientific Reports (2017).
2. Evaluating the importance of metamorphism in the foundering of continental crust. Scientific Reports (2017).
3. Reconciling the Cretaceous breakup and demise of the Phoenix Plate with East Gondwana orogenesis in New Zealand. Earth-Science Reviews (2023).
4. Detailed 40Ar/39Ar Geochronology of the Loyalty and Three Kings Ridges Clarifies the Extent and Sequential Development of Eocene to Miocene Southwest Pacific Remnant Volcanic Arcs. Geochemistry Geophysics Geosystems (2023).
5. Serpentinites of Different Tectonic Origin in an Exhumed Subduction Complex (New Caledonia, SW Pacific). Geochemistry Geophysics Geosystems (2022).