Frictional Properties and Healing Behavior of Tectonic Mélanges: Implications for the Evolution of Subduction Fault Zones

<p>Here,&nbsp;we report data from velocity-step experiments using rocks collected from ancient subduction fault zones, the Lower Mugi and Makimine m&eacute;langes of the Cretaceous Shimanto belt.&nbsp;The two m&eacute;langes 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. The compostions of the m&eacute;langes analyzed with X-ray&nbsp;diffraction (XRD) are also included in the datasets.&nbsp;Our data show that the Lower Mugi m&eacute;lange sample exhibits velocity-weakening to velocity-neutral behavior under low normal stress, and the Makimine m&eacute;lange 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 m&eacute;lange 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, which suggests&nbsp;the importance&nbsp;of&nbsp;pressure solution healing along plate interfaces.</p>