The Metamorphic Processes Group are working on a diverse range of topics, metamorphic conditions and tectonic settings. These can broadly be divided into five main themes, outlined briefly below and described in more detail in the clickable links.

High-temperature/ultra-high temperature metamorphism

The tectonic processes that lead to regional and contact metamorphism can exceed temperatures of ~800 °C, resulting in the generation of partial melts and ultimately new continental crust. Much of our work involves understanding the pressure and temperature conditions at which high temperature/ultrahigh temperature (HT/UHT) metamorphism occurs, the hand-sample-scale processes that occur under these conditions, the timescales and rates of these processes, and the tectonic mechanisms that permit such high temperatures. Results from a suite of projects (primarily involving Kristie, Victor, Mark, Bob & Besim) will provide insight into mechanisms driving extreme heat flux in crustal rocks.

Coming Soon - Learn more about: Durations & Rates of Archean orogenesis

Coming Soon - Learn more about: Timescales of granulite facies metamorphism

Coming Soon - Learn more about: UHT contact metamorphism

Devolatilization fluxes during subduction

Subduction zones represent a global “recycling center” for elements and fluids, where hydrous minerals from sediments, altered oceanic crust, and the lithospheric mantle undergo devolatilization reactions during increased pressure and temperature. The released fluids may enter the overlying mantle wedge and directly influence processes such as arc volcanism, seismicity, and the global water cycle. We are currently involved in several projects (primarily involving Mark, Besim, Jen & Hanna, and in collaboration with Ethan Baxter at Boston University) aimed at determining the timing, rates, and durations of these water-releasing metamorphic reactions, and thus the fluxes of volatiles released into the mantle wedge at depth. An additional challenge is in quantifying how much fluid is retained, to be recycled deep into the Earth’s interior.

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Chemical equilibrium and the development of metamorphic textures

Equilibrium-based thermodynamic models are often utilized to determine the conditions at which metamorphic processes occur. But how good is the assumption of equilibrium? What can these equilibrium-based models tell us about disequilibrium conditions? Does the volume of rock in apparent equilibrium for any suite of components suggest the rates of metamorphic processes? In addition to looking at these problems, we are working on projects coupling equilibrium thermodynamic predictions with deformation simulations to characterize preserved metamorphic textures and determine metamorphic evolution during collisional orogenesis. This work primarily involves Mark, Kristen & Besim.

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Novel thermobarometric/thermochronologic techniques

Various techniques can provide insight into pressure (P) and temperature (T) conditions during metamorphic processes. New methods can offer a validation of equilibrium-based thermodynamic models, or a substitute if the system in question is difficult to model. Current projects involve devising and developing alternate approaches for determining P-T-time conditions. These include using the physical (rather than chemical) properties of mineral inclusions (primarily Kyle & Mark), modeling major and trace element diffusion, and finding alternate ways of constructing phase equilibria (Mark & Victor), all to better understand the evolution of various metamorphic systems.

Learn more about: Paralyzer

Coming Soon - Learn more about: quartz inclusion Raman barometry

Coming Soon - Learn more about: small bulk-volume pseudosections

Tectonic & Metamorphic Evolution in Ductile Shear Zones

Tectonic reconstruction is reliant upon constraining the P-T-time-deformation evolution of rocks across established structural transects. In the Himalaya (Rongbuk and Sutlej Valleys) and Scotland Caledonides (Moine Supergroup), detailed structural and kinematic constraints have been established. Petrographic analysis, phase equilibria modeling and trace element thermobarometry are being applied to constrain P-T-deformation in these mylonites (Kyle, Mark, and the VT Structural Geology Group). In addition, these environments allow for the assessment of Ti redistribution resulting from recrystallizing quartz, Ti incorporation mechanisms, and the preservation of paleo-microstructures resulting from exceedingly dry quartz and sluggish diffusivities.

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