By Jason McIntosh
Modelling multiple thin intersecting veins in 3D can be an arduous task, luckily the Leapfrog vein modelling tool is perfect for visualising thin intersecting vein systems. Complex vein systems are common in many geological settings, but for the purpose of this blog I’m going to focus on shear zone vein systems. So bear with me as I attempt to sum up the characteristics of metalliferous shear zone ore deposits and how they can be modelled using Leapfrog Geo in an easily digestible blog.
A shear zone is a discontinuity surface in the Earth’s crust and upper mantle. Depending on the characteristics of the shear zone genesis and later regional tectonics, shear zones can form economic gold, silver, copper, lead, zinc and molybdenum deposits. However, the formation of large mineral deposits is dependent on a number of factors.
Shear zones form in brittle/ductile transition zones as metamorphic facies are uplifted during orogenic collisions. They are mineralized throughout successive cycles consisting of increased and decreased fluid pressure phases. Metamorphic compression pressurizes the fluid and seismic activity reduces the pressure by allowing the fluid to invade the country rock along grain boundaries and fractures. The successive cycles allow fluid to disperse and regenerate, therefore allowing for incremental precipitation of incompatible elements such as gold within fractures and along grain boundaries.
Characteristic veins within the Brittle-Ductile transition zone. (Image sourced from USGS).