Fluid-assisted fracturing, cataclasis, and resulting plastic flow in mylonites from the Moresby Seamount detachment, Woodlark Basin.

Speckbacher, Romed, Stipp, Michael, Behrmann, Jan H. and Heidelbach, Florian (2013) Fluid-assisted fracturing, cataclasis, and resulting plastic flow in mylonites from the Moresby Seamount detachment, Woodlark Basin. Journal of Structural Geology, 56 . pp. 156-171. DOI 10.1016/j.jsg.2013.10.001.

[img] Text
Speckbacher.pdf - Published Version
Restricted to Registered users only

Download (9Mb) | Contact

Supplementary data:

Abstract

The Moresby Seamount detachment (MSD) in the Woodlark Basin (offshore Papua New Guinea) is a large active low-angle detachment excellently exposed at the seafloor, and cutting through mafic metamorphic rocks. Hydrothermal infiltration of quartz followed by that of calcite occurred during cataclastic deformation. Subsequent deformation of these a priori softer minerals leads to mylonite formation in the MSD. This study aims at a better understanding of the deformation mechanism switch from cataclastic to plastic flow. Deformation fabrics of the fault rocks were analyzed by light-optical microscopy. Rheologically critical phases were mapped to determine distributions and area proportions, and EBSD was used to measure crystallographic preferred orientation (CPO). Strong calcite CPOs indicate dominant dislocation creep. Quartz CPOs, however, are weak and more difficult to interpret, suggesting at least some strain accommodation by diffusion creep mechanisms. When quartz aggregates are intermixed with the polymineralic mylonite matrix diffusion creep grain boundary sliding may be dominant. The syntectonic conversion from mafic cataclasites to more siliceous and carbonaceous mylonites induced by hydrothermal processes is a critical weakening mechanism enabling the MSD to at least intermittently plastic flow at low shear stresses. This is probably a crucial process for the operation of low-angle detachments in hydrated and dominantly mafic crust.

Document Type: Article
Additional Information: WOS:000327922200012
Keywords: Low-angle detachment; Hydrothermal infiltration; Quartz; Calcite; Polymineralic matrix; Dislocation creep; Diffusion creep; Interconnected layering
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.jsg.2013.10.001
ISSN: 0191-8141
Expeditions/Models/Experiments:
Date Deposited: 24 Oct 2013 09:33
Last Modified: 19 Jul 2017 12:29
URI: http://oceanrep.geomar.de/id/eprint/22262

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...