Crystallographic preferred orientations of exhumed subduction channel rocks from the Eclogite Zone of the Tauern Window (Eastern Alps, Austria), and implications on rock elastic anisotropies at great depths.

Keppler, Ruth, Ullemeyer, Klaus, Behrmann, Jan H. , Stipp, Michael, Kurzawski, Robert M. and Lokajíček, Tomas (2015) Crystallographic preferred orientations of exhumed subduction channel rocks from the Eclogite Zone of the Tauern Window (Eastern Alps, Austria), and implications on rock elastic anisotropies at great depths. Tectonophysics, 647 . pp. 89-104. DOI 10.1016/j.tecto.2015.02.011.

[img]
Preview
Text
Keppler et.al.pdf - Accepted Version

Download (3201Kb) | Preview
[img] Text
Keppler et.al.pdf - Published Version
Restricted to Registered users only

Download (4088Kb) | Contact

Supplementary data:

Abstract

Highlights

• Analysis of crystallographic preferred orientations of high-pressure polymineralic rocks by time-of-flight neutron diffraction
• Elastic properties of a complete set of subduction channel rocks calculated from their crystallographic preferred orientation
• Vp/Vs ratio and P-wave anisotropy of eclogites and metasediments
• Influence of eclogite retrogression during exhumation on their elastic properties
• Evaluation of the seismic signature of both clastic and carbonate sediments in subduction channels

Abstract

Crystallographic preferred orientations (CPO) of rocks from an exhumed subduction channel of the Alpine orogen were determined using time-of-flight neutron diffraction. This method allows the investigation of large polymineralic samples and, more importantly, the application of full pattern fit methods to constrain CPOs of mineralogically complex rocks. Samples studied include intensely deformed fresh and retrogressed eclogites, as well as metasediments, which are interleaved with the eclogites in the subduction channel. From the CPO, seismic properties of the samples were calculated. P- wave anisotropies of the eclogite samples are fairly low, with an average of about 1.5%, and mainly constrained by pronounced omphacite CPO. Growth and deformation of retrograde amphibole in the eclogites also led to a pronounced CPO, which has a large impact on seismic anisotropies by raising them to up to 3.7% and changing the orientations of velocity maxima. Elastic anisotropies of the subducted metasediments are higher (up to 7.4%) and constrained by quartz and mica CPO in clastics and by calcite CPO in marble. VP/VS ratios may help to distinguish fresh eclogites from retrogressed ones, and both rock types from mantle peridotites of downgoing lithospheric slabs in seismic imaging. Our data also indicate that subducted terrigenous sediments are not only strongly anisotropic, but also have low VP/VS ratios. This way there may be potential to image them by seismic tomography at depth in active subduction channels.

Document Type: Article
Additional Information: WOS:000353087400007
Keywords: crystallographic preferred orientation; subduction channel; elastic properties; P-wave anisotropy; Eclogite Zone; retrogression of eclogites
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.tecto.2015.02.011
ISSN: 0040-1951
Date Deposited: 16 Mar 2015 08:42
Last Modified: 13 Apr 2017 07:40
URI: http://oceanrep.geomar.de/id/eprint/28034

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...