On the Integration of Micro-textural and Crystal-Chemical Data With Magma Chamber Dynamics

Many magmatic systems display a dual nature: compositional uniformity at the macro-to-meso scales, and great complexity of provenance, textures and age at the micro-to-meso scale. The integration of microtextural and crystal-chemical data with dynamic models and U-series age dating has tremendous potential to reveal the inner-workings of magmatic systems. However, a means of extending that crystal-scale data back to the largest scales is needed to evaluate the statistical significance of any conclusions drawn on the basis of a few crystals or thin sections. We will address two aspects of this: 1) The application of various statistical tools for the ordering of geochemical information to yield crystal populations who share distinct chemical environments and, 2) exemplify how dynamic templates of crystal dispersal and gathering, linked with kinetics, can reveal the timescales of the emergence, persistence and decay of regions of distinct chemical potential and the corresponding crystal-cargo. We will reprise Wallace and Bergantz (2005), which introduced the concept of the shared characteristics diagram as an organizational framework for crystal zoning that compares information from different phases and chemical tracers, in a common framework. It combines elements of cluster and structured data analysis to create a crystal phylogeny. This allows one recognize the progression of shared environments in the crystal-cargo at any level of statistical significance. We will then use numerical experiments of multiphase reacting flow to illustrate how various regions of distinct compositional character arise, and the controls on how that information is propagated to resident crystals. We will illustrate the diversity of outcomes that even simple open-systems produce, and how the ratio of the Damkohler (kinetic reaction time scale to diffusion time) and Peclet (convection time scale to diffusion time) numbers can be used to characterize both simple and competitive-consecutive reactions. This ratio of dimensionless numbers yields the characteristic time for reaction to that of convection. To first order, this allows one to explore and rationalize the interplay between equilibrium as dictated by the (changing) far-field environment at the largest scales, mediated by the kinetics at the crystal interface. Wallace, G., Bergantz, G.W., 2005, "Reconciling heterogeneity in crystal zoning data: An application of shared characteristic diagrams at Chaos Crags, Lassen Volcanic Center, California," Contrib. Min. Pet., v. 149, p. 98-112.