Christopher Gerbi - Current projects
My current projects center around transferring field observations to quantifiable rheological properties in the crust. I think of it as providing “ground truth” and insight for geodynamic models. Thus my projects span the gamut of field to analytical to modeling approaches. And as with all of us in the Geodynamics group, much of this work is in collaboration with students.
Speaking of which, I am always looking for strong, motivated students (either M.S. or Ph.D). So if you are interested in any of the projects below, please contact me. I am also always open to discussing and likely supervising projects related to SEM-EBSD-CL microanalysis, rheology, U-Pb geochronology, metamorphic petrology, and Appalachian tectonics.
An example of hydration-induced weakening during retrogression from a granulitic block to an amphibolite-facies shear zone
1. Mechanisms and magnitude of syntectonic weakening. This is a nearly ubiquitous process, but most geodynamic models do not account for it. This work is the centerpiece of my research program at the moment, with several subprojects. The essential question is:
How much can the middle to lower orogenic crust change strength through metamorphic reactions, water infiltration, development of shear zones, and other processes?
The field areas are southern Ontario (see maps of near Parry Sound and the Bustard Islands) and western Maine-northern New Hampshire. Most of the work to date is based out of the Ontario field area. (Which, by the way, is a great place to work! Extensive exposure, travel by boat, beautiful rocks…) Some of the results are in a recently-published paper.
2. Evaluating the effect of (1) on orogen development.
A natural shear zone (white) system whose bulk properties depend on the strength contrast between the shear zones (white) original rock (black), their modal fractions, and their geometrical arrangement.
Using numerical modeling, we are evaluating the importance of different scales and magnitudes of synorogenic weakening on orogen evolution.
3. Measures of mechanical anisotropy. Mechanical anisotropy leads to many of the structures we observe in the Earth, yet it has not been very well quantified in natural rocks. Through field measurements, crystallographic fabric determination, and numerical modeling, we are exploring a range of naturally-deformed rocks.
4. Characterizing the bulk rheological properties of multi-phase materials. Having good constraints on the rheology of the various parts of the crust is paramount for addressing problems of crustal deformation from post-glacial rebound to orogen development. Using numerical modeling, we are exploring methods for evaluating the bulk properties of regions that contain strength heterogeneities.