U–Pb zircon dating of post-obduction volcanic-arc granitoids and a granulite-facies xenolith from New Caledonia. Inference on Southwest Pacific geodynamic models. - INSU - Institut national des sciences de l'Univers Access content directly
Journal Articles International Journal of Earth Sciences Year : 2007

U–Pb zircon dating of post-obduction volcanic-arc granitoids and a granulite-facies xenolith from New Caledonia. Inference on Southwest Pacific geodynamic models.

Abstract

In New Caledonia, the occurrence of one of the World's largest and best-exposed subduction/ obduction complex is a key point for the understanding of the geodynamic evolution of the whole Southwest Pacific region. Within the ophiolite, pre-and postobduction granitoids intrude the ultramafic allochthon and provide new time constraints for the understanding of obduction processes. At 27.4 Ma, a new East-dipping subduction generated the active margin magmatism along the western coast of the island (Saint-Louis massif). At 24.3 Ma, the eastward shift of the magma activity and slightly different geochemical features (Koum-Borindi massif) was either related to the older slab break-off; or alternatively, due to the eastward migration of the mantle wedge following the collision of the eastern margin of the Low Howe rise. Finally, the occurrence of a granulite-facies xenolith in the Koum-Borindi massif with comparable 24.5 Ma U–Pb zircon age and isotopic features (initial eNd = 5.1) suggests that these evolved magmas were generated within the lithospheric mantle beneath a continental crust of normal thickness. Geochronological evidence for continuous convergence during the Oligocene infers an East-dipping Eocene-Oligocene subduction/obduction system to have existed in the Southwest Pacific from the d'Entrecasteaux zone to the North Island of New Zealand.
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Dates and versions

hal-00109994 , version 1 (26-10-2006)

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Jean-Louis Paquette, Dominique Cluzel. U–Pb zircon dating of post-obduction volcanic-arc granitoids and a granulite-facies xenolith from New Caledonia. Inference on Southwest Pacific geodynamic models.. International Journal of Earth Sciences, 2007, 96, pp.613-622. ⟨10.1007/s00531-006-0127-1⟩. ⟨hal-00109994⟩
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