No abstract

Pseudotachylytes are generated by the cooling and solidification of frictional melt produced along a fault surface during seismic slip. Pseudotachylytes can, therefore, provide important constraints on thermal histories of faults during coseismic slip: survivor clast mineralogies and quenched crystallite morphologies have previously been used to constrain the peak temperatures during slip. Here we show that silicon‐diffusion gradients are preserved around quartz survivor clasts and that these can be used to constrain the immediate cooling histories of pseudotachylytes after the cessation of slip. The variation of diffusion length with position in pseudotachylyte veins can be well reproduced by combining simple thermal history models with Arrhenius parameters for diffusion of appropriate magma compositions.

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By the use of water absorption data (rate and equilibrium), the diffusivity of distilled and salt water through Neoprene, styrene‐butadiene, and ethylene‐propylene‐diene elastomers was predicted. Activation parameters were calculated from the Arrhenius plots and were used to calculate heats of solution (all negative). Solubility coefficients (S) were calculated from permeability (P) and diffusion (D) coefficients. For all materials salt water showed a lower D than distilled water but a higher S and P.