BED FLUIDIZATION EXPERIMENTS AS MAGMA CHAMBER ANALOGS

The concept of a magma chamber has undergone an evolution over recent decades. Magma chambers are not giant vats of crystal-free magma, and instead, there is a growing body of evidence in support of many magmatic bodies containing significant volume fractions of solids throughout their emplacement history. If this is the case, then new phenomena need to be considered when inferring magmatic processes from product. In this study, we consider one such process--bed fluidization. Bed fluidization occurs when melt percolation through a packed granular bed is sufficient to unpack grains, converting the mass into a mobile slurry. Our model investigates the effects of bed fluidization in a system scaled to represent a mafic slurry with melt percolation from below. The analogs selected are styrene butadiene (plagioclase), polycarbonate (pyroxene), and water (basaltic melt). We allow for these particles to range in sizes, approximating a polydisperse, straight line CSD, by calculating the mass required for each size fraction. Additionally, we utilize particle sizes that have low Particle Reynold’s Number to better approximate grains in magmatic systems. These analog particles are loaded into a Hele-Shaw cell, and water is injected at a controlled flux rate. Repeating the experiment for different flux rates allows for the mapping of resulting features across a range of conditions. These experimental results are extrapolated to magmatic systems through the Ergun Number—a dimensionless parameter that can be used to predict under what conditions bed fluidization occurs. Specifically, we compare the results of these experiments to features observed in the Basement Sill of the McMurdo Dry Valleys, Antarctica, where spectacular unmixing of plagioclase and orthopyroxene have occurred.