Collaborative Research: Petrological controls on continental uplift: static- and reactive-transport modeling of hydration-driven de-densification

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The geological processes that form broad, high-elevation plateaus in otherwise stable and low-lying continental interiors are poorly understood. Yet, such uplift can have profound effects on many aspects of the whole earth system, including atmospheric circulation and biodiversity. Ultimately, the causes of plateau uplift are driven by deep-seated processes within the Earth's crust and lithosphere, but due to inaccessibility, such processes remain enigmatic. A recently proposed hypothesis suggests that the addition of hydrous fluids and/or water to nominally dry lower crust could cause mineral reactions that result in significant changes in density and volume, leading to expansion and therefore surface uplift. However, the magnitude of these changes as functions of rock composition, proportion of fluid added, and depth below the Earth's surface are unquantified. The proposed study addresses this knowledge gap by performing laboratory analysis on rocks collected from the Colorado Plateau, USA, and computational modeling to produce a new predictive toolbox that can constrain the topographic effects of crustal hydration in any geological scenario worldwide. This research will train one new PhD student, two undergraduate students from underrepresented backgrounds, and promote new collaboration between two US-based early-career researchers.The tectonic effects of crustal hydration are poorly understood, owing to the absence of realistic modeling frameworks for quantifying the petrophysical effects of fluid-rock interaction at middle- to lower-crustal metamorphic conditions. This research aims to directly address this issue by employing recently developed algorithms that quantify the evolution of open and closed petrological systems using equilibrium thermodynamics. Both 1-D and 2-D algorithms will be produced that quantify the relationships between pressure, temperature, bulk-rock density, hydration state, and surface uplift, which can be applied to any crustal environment where fluid-rock interaction takes place. This will also address both closed- and open-system geological scenarios, considering small-scale and short-term fluid influx (e.g. crystallizing magmas) to large-scale, continuous fluid influx (e.g. devolatilization of a subducting slab). Predictions made for intercontinental plateau formation will be ground-truthed by measuring mineral compositions and water contents within natural samples exposed from different levels of the Colorado Plateau crust, as determined by electron probe microanalysis, electron backscatter diffraction, and secondary ion mass spectrometry. The results of this work will assist in deciphering the driving force for its uplift during the Cenozoic and the extent to which fluids released from the subducted Farallon slab were partitioned between the intermediate lithospheric mantle and the lower/middle continental crust.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.