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The metamorphic sole of New Caledonia ophiolite: 40Ar/ 39Ar, U-Pb, and geochemical evidence for subduction inception at a spreading ridge
journal contribution
posted on 2023-05-17, 14:54 authored by Cluzel, D, Jourdan, F, Sebastien MeffreSebastien Meffre, Maurizot, P, Lesimple, SAmphibolite lenses that locally crop out below the serpentinite sole at the base of the ophiolite of New Caledonia (termed Peridotite Nappe) recrystallized in the high-temperature amphibolite facies and thus sharply contrast with blueschists and eclogites of the Eocene metamorphic complex. Amphibolites mostly display the geochemical features of MORB with a slight Nb depletion and thus are similar to the youngest (Late Paleocene-Eocene) BABB components of the allochthonous Poya Terrane. Thermochronological data from hornblende ( 40Ar/ 39Ar), zircon, and sphene (U-Pb) suggest that these mafic rocks recrystallized at ∼56Ma. Using various geothermobarometers provides a rough estimate of peak recrystallization conditions of ∼0.5GPa at ∼800-950C. The thermal gradient inferred from the metamorphic assemblage (∼60°Ckm -1), geometrical relationships, and geochemical similarity suggest that these mafic rocks belong to the oceanic crust of the lower plate of the subduction/obduction system and recrystallized when they subducted below young and hot oceanic lithosphere. They were detached from the down-going plate and finally thrust onto unmetamorphosed Poya Terrane basalts. This and the occurrence of slab melts at ∼53Ma suggest that subduction inception occurred at or near to the spreading ridge of the South Loyalty Basin at ∼56Ma. © 2012. American Geophysical Union. All Rights Reserved.
Funding
Australian Research Council
AMIRA International Ltd
ARC C of E Industry Partner $ to be allocated
Anglo American Exploration Philippines Inc
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Australian National University
BHP Billiton Ltd
Barrick (Australia Pacific) PTY Limited
CSIRO Earth Science & Resource Engineering
Mineral Resources Tasmania
Minerals Council of Australia
Newcrest Mining Limited
Newmont Australia Ltd
Oz Minerals Australia Limited
Rio Tinto Exploration
St Barbara Limited
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University of Melbourne
University of Queensland
Zinifex Australia Ltd
History
Publication title
TectonicsVolume
31Article number
TC3016Number
TC3016Pagination
1-18ISSN
0278-7407Department/School
School of Natural SciencesPublisher
Wiley-Blackwell Publishing, Inc.Place of publication
111 River St, Hoboken, NJ 07030 United StatesRights statement
Copyright 2012 American Geophysical UnionRepository Status
- Restricted