Fault stepovers and gold mineralisation

Steven Micklethwaite

Research output: Contribution to conferenceAbstract


The nucleation, growth and geometric properties of faults are critical to our understanding of fluid flow and mineralisation. Notably, many gold deposits have a spatial association with step-overs on large faults, although they tend to be hosted on subsidiary structures distributed away from the step-overs. Here, fault step-overs are examined from ancient, mineralised fault systems and compared to a control population of faults, comprising active fault systems and non-mineralised well-exposed fault systems. It is demonstrated that gold deposits are anomalously associated with underlapping fault step-overs. Underlap is typically rare in fault systems. The aspect ratios of underlapping mineralised step-overs may be scale-invariant across two orders of magnitude, similar to overlapping step-overs from the control population, though more data is required. Coulomb failure stress change calculations explain why underlap is necessary for the development of the observed distributions of gold deposits around step-overs. Field observations suggest that underlapping step-overs develop due to reactivation of pre-existing structures, or the presence of mechanical heterogeneities.
Original languageEnglish
Number of pages4
Publication statusPublished - 2013
Externally publishedYes

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