ABSTRACT Spatial-Statistical Properties of Geochemical Variability as Constraints on Magma Transport and Evolution Processes at Ocean Ridges

The research presented in this thesis employs spatial and statistical properties of major element variability in basaltic lavas and mantle residues to constrain some of the processes and dynamics occurring beneath ocean ridge magmatic systems. Ocean ridges represent a critical setting for many geochemical fractionation processes involved in the chemical evo-lution of the silicate Earth, and are fundamental to the plate tectonic cycle. Because of the inherent inaccessibility, it remains an ongoing challenge to interpret the geochemistry of ocean ridge lavas and exposed mantle residues in order to extract information about the petrogenetic and geodynamic workings of ocean ridge magmatic systems. This endeavor continues to require a concerted effort, incorporating field work, laboratory experimentation and quantitative modeling, in which the identification of features in the spatial or statistical distribution of geochemical variability represents an important contribution. In the three main chapters of this thesis, I apply techniques of exploratory data analysis, computational statistics, and petrologic modeling to develop original ideas about the relationship between sampled major element variability and the effects of specific processes, both petrogenetic and scientific: crystallization, melt transport, and sampling