Abstract We present the results of U–Pb dating of zircons of two Late Permian igneous rocks from the Dun Mountain–Maitai and Brook Street terranes of New Zealand's South Island. A conglomerate clast of hornblende diorite from the Early–Middle Triassic Stephens Subgroup, Maitai Group, gives an age of 251.1 ± 1.6 Ma. A sample of hypabyssal andesite–microdiorite (Weetwood Formation) that intrudes the Late Permian Productus Creek Group of the Brook Street Terrane gives an age of 258.8 ± 7.9 Ma. The intermediate and subalkaline geochemistry of the two samples is not distinctive of specific tectonic settings, but their ages match plutons of the I-type, subduction-related Longwood Suite of the nearby Median Batholith. Assuming that correlation with the Longwood Suite is correct, the Weetwood sample increases the known areal extent of intrusion of the Longwood Suite; and the Stephens Subgroup Formation clast is consistent with a detrital link between Gondwana and the Dun Mountain–Maitai Terrane by the Middle Triassic. However, because of uncertainties regarding the timing of magmatism along other parts of the Gondwana margin, the data in this paper do not establish any specific provenance links.

Abstract: Volcanism of Late Cretaceous–Miocene age is more widespread across the Zealandia continent than previously recognized. New age and geochemical information from widely spaced northern Zealandia seafloor samples can be related to three volcanotectonic regimes: (1) age-progressive, hotspot-style, low-K, alkali-basalt-dominated volcanism in the Lord Howe Seamount Chain. The northern end of the chain ( c. 28 Ma) is spatially and temporally linked to the 40–28 Ma South Rennell Trough spreading centre. (2) Subalkaline, intermediate to silicic, medium-K to shoshonitic lavas of >78–42 Ma age within and near to the New Caledonia Basin. These lavas indicate that the basin and the adjacent Fairway Ridge are underlain by continental rather than oceanic crust, and are a record of Late Cretaceous–Eocene intracontinental rifting or, in some cases, speculatively subduction. (3) Spatially scattered, non-hotspot, alkali basalts of 30–18 Ma age from Loyalty Ridge, Lord Howe Rise, Aotea Basin and Reinga Basin. These lavas are part of a more extensive suite of Zealandia-wide, 97–0 Ma intraplate volcanics. Ages of northern Zealandia alkali basalts confirm that a late Cenozoic pulse of intraplate volcanism erupted across both northern and southern Zealandia. Collectively, the three groups of volcanic rocks emphasize the important role of magmatism in the geology of northern Zealandia, both during and after Gondwana break-up. There is no compelling evidence in our dataset for Late Cretaceous–Paleocene subduction beneath northern Zealandia. Supplementary material: Trace element compositions of zircons and whole-rock chemical compositions obtained by previous studies are available at: https://doi.org/10.6084/m9.figshare.c.3850975