Chapter 3: Pre-Late Cretaceous basement terranes of the Gondwana active margin of New Caledonia
Published:June 16, 2020
P. Maurizot, D. Cluzel, S. Meffre, H. J. Campbell, J. Collot, B. Sevin, 2020. "Chapter 3: Pre-Late Cretaceous basement terranes of the Gondwana active margin of New Caledonia", New Caledonia: Geology, Geodynamic Evolution and Mineral Resources, P. Maurizot, N. Mortimer
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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.
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New Caledonia: Geology, Geodynamic Evolution and Mineral Resources
CONTAINS OPEN ACCESS
This memoir summarizes current knowledge on the geology of New Caledonia, its geodynamic evolution and mineral resources, based on published and unpublished information. It comprises ten research papers, each addressing a particular geological assemblage or topic. After an introductory chapter and a review of the published geodynamic models of evolution of the SW Pacific, Chapters 3-5 focus on the main geological assemblages of Grande Terre: the pre-Late Cretaceous basement terranes, the Late Cretaceous to Eocene cover, and the Eocene Subduction-Obduction Complex, one of the largest and best-preserved in the world. Chapter 6 is devoted to the Loyalty Islands and Ridge. Chapter 7 deals with the mostly terrestrial post-obduction units, including regolith. Chapter 8 deals with palaeobiogeography and discusses plausible scenarios of biotic evolution. Chapters 9 and 10 provide a comprehensive review of New Caledonia's mineral resources. The volume will be of interest to stratigraphers, sedimentologists, marine geologists, palaeontologists, palaeogeographers, igneous and metamorphic petrologists, geochemists, geochronologists, and specialists in tectonics, geodynamic evolution, regoliths, ophiolites and economic geology.