Abstract The basement under the Late Cretaceous unconformity in New Caledonia consists of three amalgamated terranes. They are all oceanic, arc-related and developed offshore from the eastern Gondwana active margin during periods of marginal basin development. Téremba Terrane is composed of deep sea Permian to Mesozoic arc-derived volcanic rocks and greywackes. The Koh–Central Terrane includes at its base an ophiolite with island arc tholeiites and boninites (Koh Ophiolite) of Late Carboniferous to Early Permian age overlain by a thick sequence of greywacke (Central Range Volcaniclastic Rocks) of Permian to Late Jurassic age. The Téremba Terrane and the Koh–Central Terrane may be part of the same forearc basin, with the rocks from the Koh–Central Terrane deposited in a deeper environment. The Boghen Terrane is a metamorphic complex composed of schists, broken formations and mafic–ultramafic mélange, derived from mixed terrigenous and volcanic sources. The overall fine grain size and laminar bedding suggest deep sea and more distal deposition than the other terranes. The maximum depositional ages from detrital zircons suggest deposition during the Early Jurassic to Early Cretaceous. The terrane is interpreted as a metamorphosed subduction complex that includes blueschist and greenschist facies metamorphic rocks exhumed through the Koh–Central Terrane. At a regional scale, the nature of these three pre-Late Cretaceous terranes confirms the existing palaeogeographical reconstructions, which locate New Caledonia outboard the ocean–continent subduction that surrounded Gondwana during the Paleozoic and Early Mesozoic. A detailed analysis of these terranes and their relationship with East Australian terranes of the same age shows that a marginal basin system probably existed between mainland Gondwana and proto-New Caledonia and closed before the Late Cretaceous. A tentative detailed reconstruction of this margin during the Carboniferous–Early Cretaceous period is proposed.

Abstract The post-obduction formations of Grande Terre, New Caledonia, comprise igneous intrusions, regolith cover, and marine and terrestrial sedimentary rocks. Two restricted Late Oligocene granitoid bodies are intruded into the Peridotite Nappe and its substrate in the south of the island. Thick regolith cover developed over the Peridotite Nappe from the Late Oligocene or earlier. The Népoui Group comprises Late Oligocene–Early Miocene mixed marine carbonate and siliciclastic deposits. It mainly reworks the Peridotite Nappe and its regolith cover. Its development pattern is mainly controlled by tectonic uplift and subsidence. The Gwa N'Doro Formation on the eastern coast and the Fluvio-lacustrine Formation in the south are remnants of the Miocene–Present river network. Offshore, thick Oligocene to Neogene sedimentary successions are imaged by seismic surveys on the margins of Grande Terre, although these successions have not been drilled and remain undated. Several dredges have recovered shallow Miocene sedimentary rocks, indicating substantial Neogene subsidence. Quaternary formations are represented inland by aeolianite, vertisols and calcrete and offshore by the large barrier reef–lagoon complex, the onset of which is dated at c. 400 ka. This chapter discusses the different models proposed for the post-obduction evolution of Grand Terre.

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

Abstract This paper documents the first detailed structural analysis of the Lüliang Massif in the Trans-North China Belt, North China Craton. A nappe, made up of a Terrigeneous and Mafic Unit (TMU) derived from an oceanic basin thrust over gneisses and volcanic-sedimentary rocks, is interpreted as a magmatic arc deposited upon a TTG basement. The nappe is rooted to the west in the Trans-North China Suture that separates the Fuping Block from the Western Block. Nappe stacking, coeval with a top-to-the-SE synmetamorphic D 1 event, is dated around 1890–1870 Ma using chemical U–Th/Pb EPMA datings on monazite and U–Pb LA-ICP-MS dating on zircon. A second D 2 ductile event, characterized by SE-verging folds, reworks the D 1 structures. D 2 is the first event recorded in the late-orogenic sedimentary series that unconformably covers the metamorphic units formed during D 1 . These lithological, structural and geochronological results are correlated with those described in the eastern massifs of Hengshan, Wutaishan and Fuping. The Trans-North China Belt resulted from the collision of the Fuping Block and the Western Block after a westward-directed subduction and subsequent closure of an oceanic basin where the TMU was deposited.

We review the tectonic evolution of the southwest Pacific east of Australia from ca 120 Ma until the present. A key factor that developed early in this interval and played a major role in the subsequent geodynamic history of this region was the calving off from eastern Australia of several elongate microcontinental ribbons, including the Lord Howe Rise and Norfolk — New Caledonia Ridge. These microcontinental ribbons were isolated from Australia and from each other during a protracted extension episode from ca 120 to 52 Ma, with oceanic crust accretion occurring from 85 to 52 Ma and producing the Tasman Sea and the South Loyalty Basin. Generation of these microcontinental ribbons and intervening basins was assisted by emplacement of a major mantle plume at 100 Ma beneath the southern part of the Lord Howe Rise, which in turn contributed to rapid and efficient eastward trench rollback. A major change in Pacific plate motion at ca 55 Ma initiated east-directed subduction along the recently extinct spreading centre in the South Loyalty Basin, generating boninitic lithosphere along probably more than 1000 km of plate boundary in this region, and growth of the Loyalty-D'Entrecasteaux arc. Continued subduction of South Loyalty Basin crust led to the arrival at about 38 Ma of the 70–60 million years old western volcanic passive margin of the Norfolk Ridge at the trench, and west-directed emplacement of the New Caledonia ophiolite. Lowermost allochthons of this ophiolite are Maastrichtian and Paleocene rift tholeiites derived from the underthrusting passive margin. Higher allochthonous sheets include a poorly exposed boninitic lava slice, which itself was over-ridden by the massive ultramafic sheets that cover large parts of New Caledonia and are derived from the colliding forearc of the Loyalty-D'Entrecasteaux arc. Post-collisional extensional tectonism exhumed the under thrust passive margin, parts of which have blueschist and eclogite facies metamorphic assemblages. Following locking of this subduction zone at 38-34 Ma, subduction jumped east-ward, to form a newwest-dipping subduction zone above which formed the Vitiaz arc, that contained elements which today are located in the Tongan, Fijian, Vanuatu and Solomons arcs. Several episodes of arc splitting fragmented the Vitiaz arc and produced first the South Fiji Basin (31-25 Ma) and later (10 Ma to present) the North Fiji Basin. Collision of the Ontong Java Plateau, a large igneous province, with the Solomons section of the Vitiaz arc resulted in a reversal of subduction polarity, and growth of the Vanuatu arc on clockwise-rotating, older Vitiaz arc and South Fiji Basin crust. Continued rollback of the trench fronting the Tongan arc since 6 Ma has split this arc and produced the Lau Basin-Havre Trough. This southwest Pacific style of crustal growth above a rolling-back slab is applied to the 600-220 Ma tectonic development of the Tasman Fold Belt System in southeastern Australia, and explains key aspects of the geological evolution of eastern Australia. In particular, collision between a plume-triggered 600 Ma volcanic passive margin and a 510–515 Ma boninitic forearc of an intra-oceanic arc had the same relative orientation and geological effects as that which produced New Caledonia. A new subduction system formed probably at least several hundred kilometres east of the collision zone and produced the Macquarie Arc, In which the oldest lavas were erupted ca 480 Ma. Continued slab rollback induced regional extension and the growth of narrow linear troughs in the Macquarie Arc, which persisted until terminal deformation of this fold belt in the late-Middle to Late Devonian. A similar pattern of tectonic development generated the New England Fold Belt between the Late Devonian and Late Triassic. Parts of the New England Fold Belt have been broken from Australia and moved oceanward to locations in New Zealand, and on the Lord Howe Rise and Norfolk – New Caledonia Rise, during the post-120 Ma breakup. Given that the Tasman Fold Belt System grew between 600 and 220 Ma by crustal accretion like the southwest Pacific since 120 Ma, facing the open Pacific Ocean, we question whether the eastern (Australia–Antarctica) part of the Neoproterozoic Rodinian supercontinent was Joined to Laurentia.