Fault plane processes and mesoscopic structure of a strong-type seismogenic fault in tonalites (Adamello batholith, Southern Alps)

We envision two models for the evolution of the Gole Larghe Fault. In both models synkinematic fluid-rock interaction along a fault causes fault hardening by precipitation of abundant K-feldspar+epidote (and minor chlorite) in the cataclasite matrix conducive to final production of pseudotachylyte. In the first model, induration occurs progressively by differential precipitation related to fabric evolution in cataclasites. In the second model, induration occurs abruptly dependent on the development of full connectivity within the fault network and to fluid reservoir. Whatever the model, the Gole Larghe Fault represents a strong fault, where hardening processes resulted in a low displacement/fault thickness ratio and contrast with many mature weak faults where localized repeated seismic slip along the same weak horizons yields high displacement/fault thickness ratios.