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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, S
Amphibolite 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

AngloGold Ashanti Australia Limited

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

Teck Cominco Limited

University of Melbourne

University of Queensland

Zinifex Australia Ltd

History

Publication title

Tectonics

Volume

31

Article number

TC3016

Number

TC3016

Pagination

1-18

ISSN

0278-7407

Department/School

School of Natural Sciences

Publisher

Wiley-Blackwell Publishing, Inc.

Place of publication

111 River St, Hoboken, NJ 07030 United States

Rights statement

Copyright 2012 American Geophysical Union

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

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