Transient permeability in fault stepovers and rapid rates of orogenic gold deposit formation

• Published in: Crustal Permeability pp. 249 - 259
• Main Authors: Micklethwaite, Steven, Ford, Arianne, Witt, Walter, Sheldon, Heather A
• Format: Book Chapter
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 17.01.2012
• Subjects: fault stepovers; geothermal fields; hydrocarbons; migration; mineralised stepovers; orogenic gold deposit formation; stepover geometries; time‐integrated fluid fluxes; transient permeability
• ISBN: 9781119166566; 111916656X
• DOI: 10.1002/9781119166573.ch20

Stepovers exert a critical influence on crustal permeability and are known to control phenomena such as migration of hydrocarbons and location of geothermal fields. This chapter presents a systematic examination of the relationship between fault stepovers and ore deposits to provide insight into a primary control on permeability within continental crust at length scales of tens to thousands of kilometres, integrated over timescales of ore deposit formation. It considers accurate deposit‐scale maps of stepovers associated with gold deposits from around the world to examine the geometry, aspect ratios and scaling properties of those stepovers. The chapter assess the influence of stepover geometries on the shear and normal stress changes that occur during earthquake or fault creep events and the implications these have for fracturing. It reviews and discusses the results of experiments in terms of transient enhancement of permeability through the Earth's crust and the profound implications they have for time‐integrated fluid fluxes.