Textures of eclogites and blueschists from Syros island, Greece: inferences for elastic anisotropy of subducted oceanic crust.

Keppler, Ruth, Behrmann, Jan H. and Stipp, Michael (2017) Textures of eclogites and blueschists from Syros island, Greece: inferences for elastic anisotropy of subducted oceanic crust. Open Access Journal of Geophysical Research: Solid Earth, 122 (7). 5306-5324 . DOI 10.1002/2017JB014181.

[img]
Preview
Text
jgrb52181.pdf - Accepted Version

Download (1539Kb) | Preview

Supplementary data:

Abstract

Many blueschists and eclogites are inferred to have formed from oceanic basalts in subducted slabs. Knowledge of their elastic behaviour is essential for reconstructing the internal structure of subduction zones. The Cycladic Blueschist Unit, exposed on Syros Island (Greece), contains rocks belonging to an exhumed Tertiary subduction complex. They were possibly part of a subduction channel, a shear zone above the subducting slab in which exhumation is possible during subduction. Intense plastic deformation, forming crystallographic preferred orientations (CPO), accompanied blueschist and eclogite metamorphism. CPO of the constituent minerals in the collected samples was determined by time-of-flight neutron diffraction. Two samples are foliated fine-grained blueschists with strong CPO, rich in glaucophane, zoisite and phengite. Two coarser-grained eclogite samples rich in omphacite and clinozoisite, or glaucophane, have weaker CPO. Vp and Vs anisotropies were computed from the orientation distribution function and single-crystal elastic constants. All samples show velocity maxima parallel to the mineral lineation, and minima normal to the foliation, providing important constraints on orientations of seismic anisotropy in subduction channels. Vp anisotropies are up to three times higher (6.5-12%) in the blueschists than in the eclogites (3-4%), pointing to a potentially important lithological control of elastic anisotropy in subducted oceanic crust.

Document Type: Article
Keywords: elastic anisotropy; crystallographic preferred orientation; subduction zones; high pressure rocks; rock physical properties
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/2017JB014181
ISSN: 0148-0227
Date Deposited: 07 Jul 2017 07:45
Last Modified: 01 Feb 2019 15:16
URI: http://oceanrep.geomar.de/id/eprint/38762

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...