Episodic behavior of the eastern Gondwanan margin: Insights from detrital zircon petrochronology from the Murihiku Terrane, New Zealand

Abstract

Late Paleozoic and Mesozoic tectonostratigraphic terranes are exposed in New Zealand and New Caledonia but their original positions and tectonic configuration along the eastern Gondwanan margin are not well understood. To better constrain Mesozoic reconstructions, we sampled marine and non-marine sandstones in the Murihiku Terrane (New Zealand) and obtained 935 new UPb detrital zircon ages and trace-element data. Our results show that late Permian to Early Triassic volcaniclastic successions in the Murihiku Terrane are characterized by unimodal age spectra (260–245 Ma), indicating a proximal arc source. In contrast, a mixed provenance is recognized in Middle Triassic to Late Jurassic rocks, containing Devonian–Triassic (380–240 Ma) and Triassic–Jurassic (240–145 Ma), as well as minor early Paleozoic–Proterozoic (500–1000 Ma) detrital zircon ages. The detrital zircon age spectra from the Murihiku Terrane match magmatic pulses in the adjacent Tuhua Intrusives (Median Batholith), which is thus interpreted as the main source of the detrital sediments. Our petrochronological data show that a prominent change in the sandstone provenance occurred at 235–230 Ma, simultaneously with the transition from the Longwood Suite (261–252 Ma) to the Darran Suite (232–125 Ma) magmatism in the Median Batholith. The transitional period at 235–230 Ma also overlaps with an episode of magmatism, deformation, and uplift in New Caledonia and eastern Australia (Hunter-Bowen Orogeny). We therefore conclude that this ubiquitous tectonic episode, during the Late Triassic, marks a large-scale secular change within the Gondwanide Orogen, which was possibly driven by increased convergence rates following a plate reorganization event.