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Frictional Properties and Healing Behavior of Tectonic Mélanges: Implications for the Evolution of Subduction Fault Zones
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  • Tsai-Wei Chen,
  • Raphael Affinito,
  • Chris Marone,
  • Donald M. Fisher,
  • Andrew Smye,
  • Yoshitaka Hashimoto
Tsai-Wei Chen
Pennsylvania State University

Corresponding Author:[email protected]

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Raphael Affinito
The Pennsylvania State University
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Chris Marone
Pennsylvania State University
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Donald M. Fisher
Pennsylvania State University
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Andrew Smye
Penn State University
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Yoshitaka Hashimoto
Kochi University
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Abstract

The frictional velocity dependence and healing behavior of subduction fault zones play key roles in the nucleation of stick-slip instabilities at convergent margins. Diagenetic to low-grade metamorphic processes such as pressure solution are proposed to be responsible for the change in frictional properties of fault materials along plate interfaces; pressure solution also likely contributes to the acceleration of healing according to previous studies. Here, we report velocity-step experiments using rocks collected from ancient subduction fault zones, the Lower Mugi and Makimine mélanges of the Cretaceous Shimanto belt. The two mélanges preserve paleotemperature records corresponding to the updip and downdip limits of the seismogenic zone and deformation recording a lower versus higher degree of pressure solution. Our data show that the Lower Mugi mélange sample exhibits velocity-weakening to velocity-neutral behavior under low normal stress, and the Makimine mélange sample shows velocity-strengthening behavior under high normal stress. This is consistent with the slip behavior observed at the depths they have been subducted to along the plate interface. We also perform a series of slide-hold-slide experiments under different hydrothermal conditions using the Lower Mugi mélange sample to evaluate the role of pressure solution in fault healing and its dependency on temperature. The results show that healing rates increase in tests operated at higher temperatures. The microstructures related to pressure solution found in the postexperimental gouges support the idea that the elevated healing rate can be related to pressure solution.
03 Oct 2024Submitted to ESS Open Archive
04 Oct 2024Published in ESS Open Archive