The University of Southampton
University of Southampton Institutional Repository

Life cycle of oceanic core complexes

MacLeod, C.J., Searle, R.C., Murton, B.J., Casey, J.F., Mallows, C., Unsworth, S.C., Achenbach, K.L. and Harris, M. (2009) Life cycle of oceanic core complexes Earth and Planetary Science Letters, 287, (3-4), pp. 333-344. (doi:10.1016/j.epsl.2009.08.016).

Record type: Article

Abstract

Oceanic core complexes are the uplifted footwalls of very-large-offset low-angle normal faults that exhume lower crust and mantle rocks onto the seafloor at slow-spreading ridges. Although it is suggested on the basis of numerical modelling that they form during periods of relatively reduced magma supply, little is known about how they initiate and become inactive, nor why only certain normal fault systems develop into core complexes. In this paper we present results from a near-bottom sidescan sonar/bathymetric profiler survey and sampling study of the Mid-Atlantic Ridge near 13°N that identify the critical controls on oceanic core complex development and evolution. We show that core complex detachment faults initiate as high-angle (65° ± 10°) normal faults no different from surrounding valley-wall faults and, like them, rapidly flatten to dips of 30° in response to flexural unloading; however, on certain structures slip continues rather than being relayed inward onto a new normal fault. Runaway displacement appears to be triggered primarily by local waning of magma supply below a critical threshold, then aided by strain localisation resulting from seawater penetration and talc formation along the fault zones. Spreading becomes markedly asymmetric when the core complexes are active, and volcanism is suppressed or absent. When the asymmetry is such that the detachments accommodate more than half the total plate separation the active faults migrate across the axial valley. As a consequence magma is emplaced into and captured by the footwall of the detachment fault rather than being injected into the hanging wall, explaining the frequent presence of gabbro bodies and other melt relicts at oceanic core complexes. Core complexes are ultimately terminated when sufficient magma is emplaced to overwhelm the detachment fault; in the 13°N area by neovolcanic ridges propagating laterally across them from magmatically robust segments along strike.

Full text not available from this repository.

More information

Published date: 15 October 2009
Keywords: oceanic core complex, detachment fault, Mid-Atlantic Ridge, seafloor spreading, mantle exhumation, melt emplacement, mantle lithosphere, footwall capture

Identifiers

Local EPrints ID: 69526
URI: http://eprints.soton.ac.uk/id/eprint/69526
ISSN: 0012-821X
PURE UUID: 8283e772-d0bc-427b-93ec-225724a7eb0a

Catalogue record

Date deposited: 06 Nov 2009
Last modified: 19 Jul 2017 00:11

Export record

Altmetrics

Contributors

Author: C.J. MacLeod
Author: R.C. Searle
Author: B.J. Murton
Author: J.F. Casey
Author: C. Mallows
Author: S.C. Unsworth
Author: K.L. Achenbach
Author: M. Harris

University divisions

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.

×