Our approach is to combine laboratory experiments (skilled mechanic!), microstructural analysis (nano scientist!), and digital rock physics modeling (computer geek!). Our current projects include:
1. Fracture propagation and frictional instability under varying pore fluid pressure and chemistry, with applications to faulting and earthquake mechanisms.
Significant increase in recent seismicity has been linked to injecting waste water into the crust. We study the effect of loading path and pressurization rate associated with fluid injection on slip behavior along a pre-existing fault. The experimental results show that mechanical changes in fault normal stress are more effective than pore fluid pressurization at initiating accelerated slip events. From French et al., GRL, 2016.
2. Transport properties and 3D melt distribution of partially molten mantle peridotites, with applications to magma transport at ocean ridges, subduction zones and hotspots.
Determine permeability-porosity relationship in partially molten mantle rocks using Digital Rock Physics method: a) Building a digital rock using X-ray synchrotron microtomography techniques; 2) Virtual experiments on the digital rock to obtain physical properties; 3) Quantifying relationships to better understand geological processes. From Miller et al., EPSL, 2014.
3. Reaction-induced fracturing during hydration and carbonation of olivine, with applications oceanic lithosphere dynamics and carbon sequestration.
Temporal evolution of pore geometry during olivine mineral carbonation. A) An olivine cup (made of sintered olivine aggregates) filled with olivine sands reacted with a carbon rich fluid. X-ray microtomography images of microstructure evolution after B) 8; C) 86; D) 140 hours of carbonation. Olivine sand grains in the cup (right side of the images) show considerable increase in surface roughness. Fine-grained reaction products precipitated in the interior of the cup wall appear as growing clusters with smoother textures (magenta outline). Cracks initiate at both the inner and outer surfaces of the cup wall after 64 hours of reaction. Cracks widen as reaction continue. From Zhu et al., GRL, 2016.
4. Interplay between fracturing, crystal plasticity and pressure solution in carbonate rocks, with applications to energy exploration and fault mechanics.
Solution transfer in carbonate rocks exerts significant control in rock strength and failure mode, even when solubility is small. Yield cap (the onset of significant plastic deformation) of porous limestones is sensitive to pore fluid chemistry. Rocks containing disequilibrium fluids were weaker than those with fluids in equilibrium with the mineral components. Microstructural analyses reveal that the pressure solution at grain-to-grain contacts is enhanced with the disequilibrium pore fluid, which leads to enhanced compaction. From Lisabeth and Zhu, JGR, 2015.
