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Information - TS33 Faulting, flow, and the role of fluids in crustal deformation
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Event Information |
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Faults are of major interest throughout the earth sciences, with applications spanning the fields of structural geology and tectonics, engineering and rock mechanics, and economic geology. The reasons for such wide-ranging interest are both practical and scientific, ranging from earthquake prediction to mineral discovery, and from geothermal energy to understanding the formation and geomorphology of orogens.
Faults and associated structures are largely responsible for the design and shape of the great mountain belts. These structures influence the mechanical properties and behaviour of the rock mass; the hydrology and hydrogeology of the mountain belt; and the morphology of the land surface. In particular, localisation of shear within discrete faults results in the formation of fault rocks, characterised by specific mechanical and hydrological properties. These fault rocks change during deformation, due to:
• The continuous decrease of the mean grain size; this results also in a change of the dominant deformation mechanism, from fracturing and jointing of the host rock to frictional sliding.
• The penetration of (hydrothermal) fluids and resulting chemical changes.
The formation of faults changes the characteristics of a rock mass at all scales. From orogen to outcrop-scale, faults and associated structures (shear and extensional fractures) result in disintegration of the rock mass and enhanced accessibility to several weathering processes; at smaller scales, it results in structural, hydrological (e.g., permeability), chemical and mechanical changes (e.g., shear resistance).
The permeability of fault zones is a topic of particular interest in the field of economic geology, being a key factor in determining the volume of fluid that can pass through a fault zone. The temporal and spatial evolution of permeability in fault zones depends on the rock type, strain rate, deformation regime (brittle vs. ductile), fault architecture, and many other parameters. Numerical modelling is a powerful tool to investigate the effect of varying permeability on the fluid flow regime of a deforming region, which when coupled with a reactive transport simulation can provide useful constraints for mineral exploration, and for understanding the role of faults within petroleum systems. Field and laboratory studies provide the input for such models.
Within this session we intend to discuss the continuous evolution of rock properties and deformation mechanisms within major faults, from the fault margin to the core. Topics may include field studies of fault architecture; laboratory investigations of fault rock properties; numerical or analogue modelling of deformation and reactive fluid flow in fault zones; and applications to economic geology, such as mineralisation and geothermal energy.
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