Crystallization Kinetics: Quantitative Analysis and Numerical Simulation of Metamorphic Textures

点击翻译按钮获取中文摘要

9902682CarlsonWe seek to determine the mechanisms and rates of metamorphic reactions by using high-resolution X-ray computed tomography (CT) to study porphyroblastic textures. Mechanisms of crystallization will be extracted from the X-ray CT data by means of statistical measures of the sizes and locations of crystals, electron-microprobe analysis of compositional zoning patterns in them, and comparison with the predictions of numerical simulations of crystallization under diverse kinetic controls. New numerical models will be constructed to approximate crystallization in nature more closely than was possible before, and these models will be fit to the CT data to constrain absolute reaction rates. The principal objectives of the research are: (1) to assemble a broad inventory of textural features in metamorphic rocks whose geologic settings makes them likely to reveal information about the effects on crystallization kinetics of temperature, pressure, fluid infiltration, deformation, heating rates, precursor grain size, internal diffusional competition, and interfacial-reaction rates; (2) to create models for numerical simulation of crystallization that capture the essential character of metamorphic reaction in each of these settings; and (3) to use those new methods of numerical simulation to interpret textural data, clarifying mechanisms of metamorphic reactions and quantifying the critical kinetic parameters that determine their rates.