Evolution of fracture porosity and permeability during folding by cataclastic flow: Implications for syntectonic fluid flow

Abstract

The Canyon Range Syncline, central Utah, folded and continued to tighten by cataclastic flow, where fracture-bound blocks, defined by a distributed network of mesoscale (outcrop) fracture sets slid past each other. Thin zones of microscale cataclasite coat many of the fracture-bound blocks9 surfaces. Different generations of fracture sets used to accommodate cataclastic flow have been unraveled using crosscutting relationships and are used to track different stages of the syncline9s folding history. Many of the fracture sets preserve evidence for fluid flow (such as iron-oxide precipitates) at different stages of folding. The number of generations of quartzite and iron-oxide cataclasite zones preserved along the mesoscale fractures within the Canyon Range Syncline is used here, in conjunction with mesoscale crosscutting relationships, to develop a three-dimensional kinematic model for fracturing and potential fluid flow during folding. This study shows that there is no relationship between porosity and permeability with degree of deformation, i.e., amount of folding. Also, slight lithological variations play a large role in the geometry of the interconnected fracture network.