A New 4D Imaging Method for Three-Phase Analogue Experiments in Volcanology and Other Three-Phase Systems
Abstract
Bubbles and crystals suspended in magmas interact with each other rapidly and on a small scale, which affects large-scale volcanic processes. Studying these interactions on relevant scales of time and space is a long-standing challenge. Therefore, the fundamental explanations for the behavior of bubble- and crystal-bearing magmas are still largely speculative. Recent use of synchrotron X-ray tomography on synthetic magmas has already demonstrated its potential, but cannot be applied to analogue materials, making experiments costly and slow. We demonstrate a novel methodology for imaging bubble-particle interactions in analogue suspensions by utilizing Swept Confocally Aligned Planar Excitation (SCAPE) microscopy. This method based on laser fluorescence was originally developed to image live biological processes at high speed and in 3D. It allows imaging rates of up to several hundred volumes per second (vps) on volumes up to 1 x 1 x 0.4 mm3, with a trade-off between speed and spatial resolution. We ran experiments at 10 - 20 vps with corn syrup ( 100 Pa s) and soda-lime glass beads of diameter <50 µm, contained within a vertical Delrin casing 50 x 5 x 4 mm3. The samples are imaged through a glass window 0.17 mm thick. One challenge is the need to match the refractive index of the components as closely as possible, to increase laser penetration depth. We achieve this through careful selection of particle and liquid materials, but the high refraction at bubble interfaces leads to images where only half of the bubble facing the laser can be resolved. Nonetheless, we observe particle movement and interface morphology during injection of air, silicone oil (0.01 - 0.1 Pa s), or water (10-3 Pa s). Our results reveal an initial decrease, followed by oscillations, in particle content ahead of the injected fluid front. The interface showed instabilities on the order of several particle diameters, and particles transferred from the syrup suspension to the injected liquid in experiments with water injection. The experiments are analogous to (1) bubbles growing in crystal-bearing magmas, and (2) magma mixing during recharge (possibly with phenocryst transfer). Therefore, SCAPE presents a promising technique that allows the study of small-scale interactions in two- and three-phase systems, at high imaging rates and at low cost.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V33D0254O
- Keywords:
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- 1036 Magma chamber processes;
- GEOCHEMISTRYDE: 3653 Fluid flow;
- MINERALOGY AND PETROLOGYDE: 8439 Physics and chemistry of magma bodies;
- VOLCANOLOGY