Deformation textures and mechanical behavior of a hydrated amorphous silica formed along an experimentally produced fault in chert

Nao Hayashi, Akito Tsutsumi

doi:10.1029/2010gl042943

<jats:p>We conducted a series of friction experiments on chert at intermediate to high slip velocities (<jats:italic>V</jats:italic> = 0.87 − 104 mm/s) and at low normal stress (<jats:italic>σ</jats:italic><jats:sub><jats:italic>n</jats:italic></jats:sub> = 1.5 MPa) to better understand the process of fault weakening by silica‐gel formation, as identified in previous friction experiments on quartz‐rocks. Fault weakening in chert samples occurred in association with the formation of a 0.1‐mm‐thick fault gouge layer that contains a thin, foliated layer of fine‐grained material and a cataclastically fragmented zone characterized by clast‐matrix texture. MFT‐IR and XRD analyses reveal that the fault gouge consists of a mixture of hydrated amorphous silica and quartz grains. The mechanical behavior of the fault gouge at a small magnitude of strain (<jats:italic>γ</jats:italic> = 0.008), as examined independently of the friction experiments using a rheometer, is characterized by a negative dependence of shear stress on strain rate with a notable hysteresis behavior.</jats:p>

Deformation textures and mechanical behavior of a hydrated amorphous silica formed along an experimentally produced fault in chert

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