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Boninites and adakites from the northern termination of the tonga trench: Implications for adakite petrogenesis

journal contribution
posted on 2023-05-16, 23:34 authored by Trevor FalloonTrevor Falloon, Leonid Danyushevsky, Anthony CrawfordAnthony Crawford, Sebastien MeffreSebastien Meffre, Woodhead, JD, Bloomer, Sh
Adakitic rocks were recovered by dredging from the northern termination of the Tonga Trench during the 1984 voyage of the R.V. Natsushima and the 1996 voyage of the R.V. Melville. These contain magmatic zircons that have been dated at 2·5 Ma by U-Pb methods, indicating that they are contemporaneous with boninite magmatism previously described from this area. This is the first time adakites and high-Ca boninites have been reported from the same active tectonic setting. The Tonga adakites are classified as high-SiO2 adakites, and are compositionally consistent with an origin as partial melts of subducted Pacific oceanic crust and sediment. Geochemical modelling suggests that the adakites are not involved in the petrogenesis of the Tongan high-Ca boninites. However, the recovery of adakites and boninites from the termination of the northern Tonga Trench suggests that both magma types are related to the unique tectonic setting of this region, where a transition from steep subduction to a transform fault plate boundary has created a slab window with an associated slab edge. Boninites are generated as a result of hot Samoan plume mantle moving through the slab window and subsequently being fluxed by H2O-rich fluids from the subducting Pacific oceanic crust. The Tonga adakites, in contrast, result from the direct melting of the slab edge as a result of the juxtaposition of the subducting slab against hot mantle derived from the Samoan plume. © The Author 2008. Published by Oxford University Press. All rights reserved.

History

Publication title

Journal of Petrology

Volume

49

Issue

4

Pagination

697-715

ISSN

0022-3530

Department/School

School of Natural Sciences

Publisher

Oxford Univ Press

Place of publication

Oxford, UK

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

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