Active fault and shear processes and their implications for mineral deposit formation and discovery

Mineralisation associated with fault, vein and shear zone systems can be related to processes that operated when those systems were active. Despite the complexity of processes that operate in faults, veins and shear zones, there are typically systematic patterns in geometry (e.g. segmentation and step-overs) and scaling, which are the cumulative result of multiple slip events. In turn, there are systematic patterns in individual slip events (e.g. earthquake-aftershock sequences, shear zone creep transients, earthquake swarms) with implications for permeability enhancement and mineral deposit formation. This review identifies three avenues for future research: (1) a need to improve constraints on the scaling characteristics of faults, shear zones and veins specifically related to mineralisation. (2) The integration of stress change and damage concepts with 3-D lithological observations and reactive transport modelling. (3) Understanding the impact of multiphase fluids (e.g. H2O-CO2-NaCl fluids) on fault mechanics and permeability. Static stress change modelling, damage mechanics modelling and fault/vein scaling concepts have promising predictive capabilities for the future discovery of mineral deposits. The review mostly refers to epithermal, mesothermal, and carlin-type gold deposits, but the principles could extend to any hydrothermal mineral deposit formed during faulting, fracturing and shearing. (C) 2009 Elsevier Ltd. All rights reserved.