Abstract
Dominantly Mesozoic to Proterozoic xenocrystic zircons extracted from Tiébaghi chromitite coexist with a well-defined population (30%) of Eocene magmatic grains (U-Pb: 48.2 ± 1.1 Ma). Since Eocene zircons are absent in the peridotite host rock and are accompanied by rare rutiles with the same age range, it is suggested that both are derived from the circulating melt from which the chromite ore was generated. This hypothesis is strengthened by a similar 40Ar/39Ar age of 46 ± 2 Ma on amphibole that is closely associated with chromitite. These data confirm the Eocene age and supra-subduction setting of the Tiébaghi podiform chromitite, which thus was formed by interaction of peridotite and mafic melt in the final stage of the forearc magmatic event that occurred between 55 Ma and 47 Ma. Modelling the melt associated with chromite formation using zircon trace-elements and REE-zircon partitioning coefficients suggests forearc basalt as a likely candidate and the felsic by-product of peridotite-melt interaction a source for early Eocene magmatic zircons.
Original language | English (US) |
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Article number | 104873 |
Journal | Ore Geology Reviews |
Volume | 145 |
DOIs | |
State | Published - Jun 2022 |
Bibliographical note
Funding Information:The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jonathan C. Aitchison reports financial support was provided by Australian Research Council.
Funding Information:
This article is a contribution to the ARC program DP190100814 “Diamonds In Ophiolites: Recycling Deep Mantle Into Supra-Subduction Zones” and to IGCP 649 Project “Diamonds and Recycled Mantle”. We thank Dr. Anette Von der Handt for microprobe analyses at the University of Minnesota. D.C. and J.C.A. thank M. Henri Reuillard, M. Marc Akaro and the Tiébaghi Historical Society for arranging access to the mine wash-plant. Dr. Anastassia Borisova and two anonymous reviewers are warmly thanked for thorough and constructive reviews.
Publisher Copyright:
© 2022 The Authors
Keywords
- Ar/Ar amphibole
- Chromite
- New Caledonia
- Podiform
- U-Pb zircon