Competing Diffusion Pathways in High-Temperature Metamorphic Quartz

Abstract

We present spectroscopic analyses that characterize the distribution and abundance of hydroxyl-bearing impurities within a single quartz crystal grown in hydrothermal fluid. We focus on a gemmy quartz crystal collected in a vein from the high-temperature Lepontine Zone of the Swiss Alps. We utilize high-resolution (200μm spot size) infrared spectroscopic analyses conducted on traverses across thin (~750μm) wafers cut perpendicular to the c-axis of the crystal. IR-spectra record characteristic peaks associated with HOH, LiOH and AlOH contaminant species. Species concentrations vary vertically and horizontally through the crystal both as a function of uptake during growth and diffusion following growth. We show that all concentration profiles reveal relative diffusion competing migratory pathways exist within hydrothermal quartz crystals, and that each pathway, as well as their aggregate, can provide valuable information for discerning the post-crystallization thermal histories of their host crystal. Our goal interact to produce the observed impurity gradients within the crystal.