Trace Element Crystal Growth Speedometry: Implications for Magmatic and Hydrothermal Systems

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The purpose of this study is to better understand what controls how fast crystals can grow in simple and complex natural systems. For example, crystal growth has direct implications for predicting the conditions for volcanic eruptions because crystallization may induce the formation of bubbles or increase the viscosity of magma, both of which facilitate the build-up of the over-pressures needed for eruptions. Quantifying crystal growth rates would also provide insight into how long it takes for magma bodies to grow before they erupt catastrophically, generating hazardous conditions for life and human society. Adequate methods for constraining crystal growth rate, however, remain elusive. The goal of this work is to develop and calibrate a new crystal growth speedometer based on the extent to which trace elements are incorporated into a rapidly growing crystal at levels that deviate from equilibrium. Theory will be combined with state of the art in situ analytical measurements to develop a generalized workflow for quantifying crystal growth rates. This work will have implications for 1) magma dynamics prior to eruption, 2) the rate at which faults and cracks heal after a natural or induced earthquake and 3) the rates at which economically important mineral deposits are precipitated in veins. The work also has implications for controlling the rate of latent heat release by crystallization from melts or solutions, which in turn, has implications for chemical storage of renewable energies (solar and wind). Participants of this project will also be involved in several community outreach programs in the Department of Earth, Environmental and Planetary Sciences at Rice University: 1) content production for Outcroppings, a department sponsored magazine of the Earth, environment and energy, 2) geology education with K-12 teachers and students in Houston, and 3) participation and organizing of an annual industry-Rice Earth Science symposia that brings together leaders in industry and academia to work on problems of mutual societal interest.The goal of this project is to develop a relatively new crystal growth speedometer based on disequilibrium incorporation of trace elements that would otherwise be rejected by the crystal at equilibrium (incompatible elements). This speedometer will be developed by calibrating against field studies in which crystal growth rates have been independently constrained. A fundamental objective will be to evaluate how common disequilibrium effects associated with rapid crystal growth are observed in magmatic systems. A comprehensive sampling of olivines in magmas from different tectonic and volcanic settings will be analyzed for incompatible trace elements using state of the art high resolution laser ablation inductively coupled plasma mass spectrometry and time of flight secondary ion mass spectrometry. The empirical speedometer will then be applied to olivine phenocryst populations from different magmatic settings to map out the distribution of crystal growth rates within the population, with particular emphasis on resolving the question of whether phenocrysts grow slowly in a long-lived magma chamber or instead nucleated and grew just before eruption. Insights from this work will be used to develop models for crystal growth in different geologic settings, such as during fault healing and generation of pegmatites.