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Research title Fluid flow through fault zones in granite exhumed from seismogenic depths. Summary of research Fault rock physical properties are crucial for understanding earthquake nucleation and propagation, yet little work has been done on how fluids flowing through a fault zone may alter fault rock properties. This project will examine how fracture systems in crystalline rock control fluid flow through fault zones and impact on the mineralogy, geochemistry and hence material properties of the resulting fault rocks. This requires integrating observations of fault zone structure, metamorphic responses to fluid flow and the timing of fault and fluid flow activity. Project results will provide important constraints on the mechanical and physical properties of fractured crust from seismogenic depths; crucial boundary conditions for models of earthquake nucleation and rupture and factors controlling migration of mineralizing fluids in the shallow crust and therefore the development of hydrothermal mineral deposits.
My field area is at Monte Rosa (northern Italy)where the basement gneiss has been cut by a variety of fracture systems that post-date recent Alpine metamorphism. Pilot field studies showed that several fracture generations contain signatures of the flow of different fluids. My undergraduate research also found important microstructural evidence for fluid-rock interaction in haloes around these fractures.
The distribution of altered and mineralised fault rocks, altered and unmodified host rock will be mapped at outcrop, thin section and electron microscope scales. Evidence of fluid-rock interaction will be examined at scales from individual fracture surfaces to specific grain boundaries of minerals and pervasive alteration of the host rock. This integrated systematic spatial analysis of the mineralogy, geochemistry, stable isotope geochemistry and fluid inclusion studies of the fault rocks will constrain the relative timing of fluid movement, the type of fluid that has moved through the faults and the structural locations within the complex fault zones where this flow has been focussed. Thermal conditions of the host rock during fluid flow and brittle deformation will be constrained using low temperature thermochronology.This integrated approach will allow me to couple the fluid flow history through the fractures with a model for the growth and progressive evolution of the fault systems as the granite is being exhumed toward the surface.
Supervisors Dr Zoe Shipton
Dr Tim Dempster
Dr Cristina Persano
Recent publications Lawther, S.E.M., Shipton, Z.K. & Dempster, T.J. 2008, Fluid flow through fault zones exhumed from seismogenic depths, EGU International conference, Vienna Lawther.S.E.M & Dempster.T.J. 2007. Apatite surfaces as a guide to fluid movements on grain boundaries. Geol.Soc.of London, Tectonics Studies Group Annual International Conference, Glasgow. Recent research grants | View all grants >> Shipton Z. K., Lawther S., Dempster T. and Boyce A. (SUERC). 2009-2010. Variability in fault architecture, mineralogy and fluid flow through faults in granite gneiss exhumed from seismogenic depths. NERC Isotope Geoscience Facility award IP-1156-1109, £43,200. Lawther, S. 2008. AAPG Grants in Aid, Fred A. & Jean C. Dix Named Grant $2000.
Lawther, S. 2009. Mineralogical Society postgraduate bursary. EGU meeting 2009. £400 |
