The University of Southampton
University of Southampton Institutional Repository

Backarc rifting, constructional volcanism and nascent disorganised spreading in the southern Havre Trough backarc rifts (SW Pacific)

Backarc rifting, constructional volcanism and nascent disorganised spreading in the southern Havre Trough backarc rifts (SW Pacific)
Backarc rifting, constructional volcanism and nascent disorganised spreading in the southern Havre Trough backarc rifts (SW Pacific)
High resolution multibeam (EM300 and SEABEAM) data of the Southern Havre Trough (SHT), combined with observations and sample collections from the submersible Shinkai6500 and deep-tow camera, are used to develop a model for the evolution and magmatism of this backarc system. The Havre Trough and the associated Kermadec Arc are the product of westward subduction at the Pacific–Australian plate boundary. Detailed studies focus on newly discovered features including a seamount (Saito Seamount) and a deep graben (Ngatoroirangi Rift, > 4000 m water depth floored with a constructional axial volcanic ridge > 5 km in length and in excess of 200 m high), both of which are characterised by pillow and lobate flows estimated at < 20,000 years old based on sediment cover, high reflectivity and thin Mn crusts on recovered glassy olivine basalts and basaltic andesites.

Elongate volcanic ridges at 35°15?S and 34°30?S, and backarc seamounts (35°30?S, 178°30?E) occur at the eastern margin of the SHT. Similar seafloor morphology is observed in the central and western portions of the basin, suggesting that recent volcanism may be broadly distributed across the backarc. Mass balance modelling indicates a maximum crustal thickness of ~ 11 km to < 6 km, similar to estimates of crustal thickness in the Lau Basin to the north. Given such high crustal attenuation and extensive backarc mafic magmatism within deep SHT rifts, we propose that the SHT is in an incipient phase of distributed and “disorganised” oceanic crustal accretion in multiple, ephemeral, and short but deep (> 4000 m) spreading systems. These discontinuous spreading systems are characterised by failed rifts, rift segmentation, and propagation. Successive episodes of magmatic intrusion into thinned faulted arc basement results in defocused asymmetrical accretion. Cross-arc volcanic chains, isolated volcanoes and underlying basement plateaus are interpreted to represent a “cap” of recent extrusives. However, they may also be composed entirely of newly accreted crust and the spatially extensive basement fabric of elongated volcanic ridges may be the surface expression of pervasive dike intrusion that has thoroughly penetrated and essentially replaced the original arc crust with newly accreted intrusives.

back arc basin, SW Pacific, bathymetry, tectonics, magmatism, spreading
0377-0273
39-57
Wysoczanski, R.J.
4fc6c0ac-f2ae-4df1-a161-2b97ecaa9f9a
Todd, E.
ae30eb1e-f5b2-4511-a001-b3949b474d7a
Wright, I.C.
be2a8931-3932-4f1e-b387-43e3652bf3fc
Leybourne, M.I.
ce62e938-0230-4a4e-ad12-3645858fb0c6
Hergt, J.M.
7a515189-bc9f-4701-9fd1-a5cfab91e664
Adam, C.
27292e51-0e0d-414d-b0a9-f6789d0428c3
Mackay, K.
75acea3e-41ec-4ad6-bb80-74308324c6c5
Wysoczanski, R.J.
4fc6c0ac-f2ae-4df1-a161-2b97ecaa9f9a
Todd, E.
ae30eb1e-f5b2-4511-a001-b3949b474d7a
Wright, I.C.
be2a8931-3932-4f1e-b387-43e3652bf3fc
Leybourne, M.I.
ce62e938-0230-4a4e-ad12-3645858fb0c6
Hergt, J.M.
7a515189-bc9f-4701-9fd1-a5cfab91e664
Adam, C.
27292e51-0e0d-414d-b0a9-f6789d0428c3
Mackay, K.
75acea3e-41ec-4ad6-bb80-74308324c6c5

Wysoczanski, R.J., Todd, E., Wright, I.C., Leybourne, M.I., Hergt, J.M., Adam, C. and Mackay, K. (2010) Backarc rifting, constructional volcanism and nascent disorganised spreading in the southern Havre Trough backarc rifts (SW Pacific). Journal of Volcanology and Geothermal Research, 190 (1-2), 39-57. (doi:10.1016/j.jvolgeores.2009.04.004).

Record type: Article

Abstract

High resolution multibeam (EM300 and SEABEAM) data of the Southern Havre Trough (SHT), combined with observations and sample collections from the submersible Shinkai6500 and deep-tow camera, are used to develop a model for the evolution and magmatism of this backarc system. The Havre Trough and the associated Kermadec Arc are the product of westward subduction at the Pacific–Australian plate boundary. Detailed studies focus on newly discovered features including a seamount (Saito Seamount) and a deep graben (Ngatoroirangi Rift, > 4000 m water depth floored with a constructional axial volcanic ridge > 5 km in length and in excess of 200 m high), both of which are characterised by pillow and lobate flows estimated at < 20,000 years old based on sediment cover, high reflectivity and thin Mn crusts on recovered glassy olivine basalts and basaltic andesites.

Elongate volcanic ridges at 35°15?S and 34°30?S, and backarc seamounts (35°30?S, 178°30?E) occur at the eastern margin of the SHT. Similar seafloor morphology is observed in the central and western portions of the basin, suggesting that recent volcanism may be broadly distributed across the backarc. Mass balance modelling indicates a maximum crustal thickness of ~ 11 km to < 6 km, similar to estimates of crustal thickness in the Lau Basin to the north. Given such high crustal attenuation and extensive backarc mafic magmatism within deep SHT rifts, we propose that the SHT is in an incipient phase of distributed and “disorganised” oceanic crustal accretion in multiple, ephemeral, and short but deep (> 4000 m) spreading systems. These discontinuous spreading systems are characterised by failed rifts, rift segmentation, and propagation. Successive episodes of magmatic intrusion into thinned faulted arc basement results in defocused asymmetrical accretion. Cross-arc volcanic chains, isolated volcanoes and underlying basement plateaus are interpreted to represent a “cap” of recent extrusives. However, they may also be composed entirely of newly accreted crust and the spatially extensive basement fabric of elongated volcanic ridges may be the surface expression of pervasive dike intrusion that has thoroughly penetrated and essentially replaced the original arc crust with newly accreted intrusives.

This record has no associated files available for download.

More information

Published date: 1 February 2010
Keywords: back arc basin, SW Pacific, bathymetry, tectonics, magmatism, spreading
Organisations: Marine Geoscience

Identifiers

Local EPrints ID: 66099
URI: http://eprints.soton.ac.uk/id/eprint/66099
ISSN: 0377-0273
PURE UUID: 2ecbae32-10be-4697-9c37-c07568b63e62

Catalogue record

Date deposited: 28 Apr 2009
Last modified: 13 Mar 2024 18:08

Export record

Altmetrics

Contributors

Author: R.J. Wysoczanski
Author: E. Todd
Author: I.C. Wright
Author: M.I. Leybourne
Author: J.M. Hergt
Author: C. Adam
Author: K. Mackay

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.

×