Fault Model

Fluid Transport Properties of Faults

by C.H. Scholz and M.H. Anders

A fault zone consists of two structural elements, an interior cataclasite core, consisting of wear detritus derived from the wall rocks, and a process zone wake, an envelop of cracked rock surrounding the cataclasite zone, in which the degree of cracking increases exponentially as the fault is approached. The permeability of the fault depends on the condition of both of these elements.

The full reference describing this model may be found in: USGS Workshop on "The Mechanical Involvement of Fluids on Faulting," eds. (S. Hickman, R. Sibson, R. Bruhn), pp. 247-253, USGS Open-file Report 94-228, 1994.

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Fig. 4a. Open cataclasite zone (ccz), open process zone. Fault is permeable conduit both parallel and transverse to strike. Case where protolith is clay free and fault zone is unmineralized.

Fig. 4c. Inner conduit. Active fault, process zone mineralized, cataclasite zone refractured. Transport only within ccz.

Fig. 4b. Outer conduit. Cataclasite zone is clay rich. Process zone is unmineralized.Fault is permeable along strike and in process zone andimpermeable transverse to strike.

Fig. 4d. Inactive fault: both cataclasite zone and process zone mineralized. Impermeable both parallel and transverse to strike.