Crustal structure and kinematics of the TAMMAR propagating rift system on the Mid-Atlantic Ridge from seismic refraction and satellite altimetry gravity

Kahle, Richard L., Tilmann, Frederik and Grevemeyer, Ingo (2016) Crustal structure and kinematics of the TAMMAR propagating rift system on the Mid-Atlantic Ridge from seismic refraction and satellite altimetry gravity Geophysical Journal International, 206 (2). pp. 1382-1397. DOI 10.1093/gji/ggw219.

[img]
Preview
Text
Kahle.pdf - Published Version

Download (14Mb) | Preview

Supplementary data:

Abstract

The TAMMAR segment of the Mid-Atlantic Ridge forms a classic propagating system centred about two degrees south of the Kane Fracture Zone. The segment is propagating to the south at a rate of 14 mm yr−1, 15 per cent faster than the half-spreading rate. Here, we use seismic refraction data across the propagating rift, sheared zone and failed rift to investigate the crustal structure of the system. Inversion of the seismic data agrees remarkably well with crustal thicknesses determined from gravity modelling. We show that the crust is thickened beneath the highly magmatic propagating rift, reaching a maximum thickness of almost 8 km along the seismic line and an inferred (from gravity) thickness of about 9 km at its centre. In contrast, the crust in the sheared zone is mostly 4.5–6.5 km thick, averaging over 1 km thinner than normal oceanic crust, and reaching a minimum thickness of only 3.5 km in its NW corner. Along the seismic line, it reaches a minimum thickness of under 5 km. The PmP reflection beneath the sheared zone and failed rift is very weak or absent, suggesting serpentinisation beneath the Moho, and thus effective transport of water through the sheared zone crust. We ascribe this increased porosity in the sheared zone to extensive fracturing and faulting during deformation. We show that a bookshelf-faulting kinematic model predicts significantly more crustal thinning than is observed, suggesting that an additional mechanism of deformation is required. We therefore propose that deformation is partitioned between bookshelf faulting and simple shear, with no more than 60 per cent taken up by bookshelf faulting.

Document Type: Article
Additional Information: WOS:000379772500047
Keywords: Gravity anomalies and Earth structure, Seismic tomography, Mid-ocean ridge processes, Oceanic transform and fracture zone processes, Kinematics of crustal and mantle deformation, Crustal structure, RV Meteor, M60/2
Research affiliation: GFZ
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Refereed: Yes
DOI etc.: 10.1093/gji/ggw219
ISSN: 0956-540X
Expeditions/Models:
Date Deposited: 04 Aug 2016 11:19
Last Modified: 04 May 2017 08:34
URI: http://eprints.uni-kiel.de/id/eprint/33522

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...