The University of Southampton
University of Southampton Institutional Repository

From rifting to active spreading in the Lau Basin – Havre Trough backarc system (SW Pacific): Locking/unlocking induced by seamount chain subduction

From rifting to active spreading in the Lau Basin – Havre Trough backarc system (SW Pacific): Locking/unlocking induced by seamount chain subduction
From rifting to active spreading in the Lau Basin – Havre Trough backarc system (SW Pacific): Locking/unlocking induced by seamount chain subduction
Associated with Pacific-Australia plate convergence, the Lau Basin – Havre Trough is an active back-arc basin that has been opened since ?5.5 Ma by rifting and southward propagating oceanic spreading. Current back-arc opening rates decrease from 159 mm yr?1 in the northern Lau Basin to 15 mm y?1 in the southern Havre Trough. Major tectonic changes occur at the transition between Havre Trough rifting and full oceanic spreading of the Eastern Lau Spreading Center (ELSC), where the oblique-to-trench, westward subducting Louisville Seamount Chain (LSC) sweeps southwards along the Tonga trench. New swath bathymetry, seismic reflection data, and limited rock sampling in this area constrain a tectonic and kinematic back-arc model that incorporates the effects of LSC subduction. The ELSC, which extends southward to 24°55?S, forms a deep rift valley propagating southward through older, rifted arc basement. Present-day seismicity and fresh and fractured pillow lavas at 23°42?S are consistent with rift valley neovolcanism. Conversely, the northern Havre Trough has low seismicity and rifted volcanic basement ridges trending 25–45° oblique to the basin axis consistent with low levels of extensional tectonism and volcanism. This latter structural fabric is interpreted as an early stage of rifting that is now “locked” due to compression on the arc exerted by LSC subduction, while in the Lau Basin such effects have passed as the LSC swept along the Tonga Trench. It is proposed that the Lau-Havre back-arc opening is controlled by tectonic constraints exerted at the limits of the system by the LSC subduction, which determines the southward migration of the Tonga Arc pole of rotation and associated Lau Basin opening. A discrete three-stage back-arc opening evolution is proposed, comprising: (1) an initial phase of back-arc rifting along the whole length of the plate boundary, beginning at ?6–5 Ma; (2) a subsequent phase, mostly present in the southern part of the back-arc domain and still active in the Havre Trough, of transpression and transtension, starting at ?4 Ma in the north, as the LSC starts to subduct and sweeps southward along the Tonga trench; and (3) a renewed opening phase in the northern segment of the back-arc domain, with rifting and spreading, starting at ?3.5 Ma, as subduction of the LSC along the northern Tonga trench is progressively completed.
1525-2027
art.8909
Ruellan, E.
efd7b2cb-ff69-4199-aabc-f6d5e7ef9113
Delteil, J.
94a263c6-14df-4bca-aa2a-bcc68714a6fb
Wright, I.
be2a8931-3932-4f1e-b387-43e3652bf3fc
Matsumoto, T.
7d7d9ed5-6095-4b70-b822-d64a3c8889f7
Ruellan, E.
efd7b2cb-ff69-4199-aabc-f6d5e7ef9113
Delteil, J.
94a263c6-14df-4bca-aa2a-bcc68714a6fb
Wright, I.
be2a8931-3932-4f1e-b387-43e3652bf3fc
Matsumoto, T.
7d7d9ed5-6095-4b70-b822-d64a3c8889f7

Ruellan, E., Delteil, J., Wright, I. and Matsumoto, T. (2003) From rifting to active spreading in the Lau Basin – Havre Trough backarc system (SW Pacific): Locking/unlocking induced by seamount chain subduction. Geochemistry, Geophysics, Geosystems, 4 (5), art.8909. (doi:10.1029/2001GC000261).

Record type: Article

Abstract

Associated with Pacific-Australia plate convergence, the Lau Basin – Havre Trough is an active back-arc basin that has been opened since ?5.5 Ma by rifting and southward propagating oceanic spreading. Current back-arc opening rates decrease from 159 mm yr?1 in the northern Lau Basin to 15 mm y?1 in the southern Havre Trough. Major tectonic changes occur at the transition between Havre Trough rifting and full oceanic spreading of the Eastern Lau Spreading Center (ELSC), where the oblique-to-trench, westward subducting Louisville Seamount Chain (LSC) sweeps southwards along the Tonga trench. New swath bathymetry, seismic reflection data, and limited rock sampling in this area constrain a tectonic and kinematic back-arc model that incorporates the effects of LSC subduction. The ELSC, which extends southward to 24°55?S, forms a deep rift valley propagating southward through older, rifted arc basement. Present-day seismicity and fresh and fractured pillow lavas at 23°42?S are consistent with rift valley neovolcanism. Conversely, the northern Havre Trough has low seismicity and rifted volcanic basement ridges trending 25–45° oblique to the basin axis consistent with low levels of extensional tectonism and volcanism. This latter structural fabric is interpreted as an early stage of rifting that is now “locked” due to compression on the arc exerted by LSC subduction, while in the Lau Basin such effects have passed as the LSC swept along the Tonga Trench. It is proposed that the Lau-Havre back-arc opening is controlled by tectonic constraints exerted at the limits of the system by the LSC subduction, which determines the southward migration of the Tonga Arc pole of rotation and associated Lau Basin opening. A discrete three-stage back-arc opening evolution is proposed, comprising: (1) an initial phase of back-arc rifting along the whole length of the plate boundary, beginning at ?6–5 Ma; (2) a subsequent phase, mostly present in the southern part of the back-arc domain and still active in the Havre Trough, of transpression and transtension, starting at ?4 Ma in the north, as the LSC starts to subduct and sweeps southward along the Tonga trench; and (3) a renewed opening phase in the northern segment of the back-arc domain, with rifting and spreading, starting at ?3.5 Ma, as subduction of the LSC along the northern Tonga trench is progressively completed.

This record has no associated files available for download.

More information

Published date: 2003

Identifiers

Local EPrints ID: 54960
URI: http://eprints.soton.ac.uk/id/eprint/54960
ISSN: 1525-2027
PURE UUID: 89536835-b4eb-4b48-93af-536ac6418093

Catalogue record

Date deposited: 23 Jul 2008
Last modified: 15 Mar 2024 10:51

Export record

Altmetrics

Contributors

Author: E. Ruellan
Author: J. Delteil
Author: I. Wright
Author: T. Matsumoto

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×