Kick‐and‐cook experiments on peridotite: simulating coseismic deformation and post‐seismic creep

Abstract

Experiments comprising deformation at 600°C and annealing at 700-1000°C were performed on natural peridotite to examine the microfabric evolution at conditions corresponding to those prevailing just below the seismogenic zone in suboceanic upper mantle. The found olivine microstructures indicate that deformation occurs by low-temperature plasticity. At low and high annealing temperatures, zones of high strain are replaced by subgrains and recrystallized grains respectively. The microstructures after annealing at 1000°C resemble`coreand-mantle structures´from shear zone peridotites, often interpreted as imprint of steady-state dislocation creep. Our study shows that such structures can form by a sequence of low-temperature plasticity at high stress and subsequent recrystallization at low stress, as corresponding to coseismic deformation and post-seismic creep. In this case, palaeopiezometers are not applicable and a local CPO in aggregates of new grains does not necessarily indicate the activated glide system.

Short-wavelength undulatory extinction in quartz recording coseismic deformation in the middle crust – an experimental study

“…For this stage of rapid loading, strain rate and stresses attained come close to those expected for natural deformation (Trepmann et al 2007;Druiventak et al, 2012). Consequently, microfabrics developed in these experiments are expected to correspond to those formed in nature.…”

“…Recrystallization by formation and migration of high-angle grain boundaries seems to be more effective in highly strained zones, whereas recovery predominates elsewhere (e.g. Fitz Gerald and Stünitz, 1993;Trimby et al, 1998;Passchier and Trouw, 2008;Stipp and Kunze, 2008;Druiventak et al, 2012). Accordingly, zones of intense crystal-plastic deformation resulting from the kick experiment are replaced by small new grains during the creep experiment.…”

“…Cells with high misorientation may act as seeds for the formation of new grains. Similar recrystallization microfabrics are described for olivine deformed in kick and cook experiments on peridotites (Druiventak et al 2012) and for feldspar by Stünitz et al, 2003. Whether old grains deformed in the kick experiment are replaced by new grains, or their internal structure resulting from inhomogeneous deformation evolves into SWUE by dynamic recovery, depends on strain accumulated during Fig. 9.…”

“…We follow the original concept of "kick and cook" experiments, designed to simulate coseismic loading and postseismic relaxation in the uppermost plastosphere (Trepmann et al, 2007;Druiventak et al, 2011Druiventak et al, , 2012. In this study, we replace the "cook" procedure, which denotes a stage of high temperature and nominally zero differential stress, by a more realistic "creep" stage at high temperature and moderate residual stress, during which microstructures created in the initial stage of high-stress deformation ("kick") become modified during further deformation.…”

The microstructural record of porphyroclasts and matrix of partly serpentinized peridotite mylonites – from brittle and crystal-plastic deformation to dissolution–precipitation creep

“…In comparison with experimental studies on the rheology of rock-forming minerals in metamorphic mafic to ultramafic rocks (olivine: e.g. Chopra and Paterson, 1981;Hirth and Kohlstedt, 2003;Zhang et al, 2000;Jung and Karato, 2001;Jung et al, 2006;Druiventak et al, 2011Druiventak et al, , 2012clinopyroxene: e.g. Avé Lallemant, 1978;Ingrin et al, 1992;Orzol et al, 2006;Zhang et al, 2006;Zhang and Green, 2007;Moghadam et al, 2010; antigorite: e.g.…”