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Hill, R. J.
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Hill, R. J.
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- PublicationRestrictedIn-situ degassing study on crystal-bearing Stromboli basaltic magmas: Implications for Stromboli explosions(2011-09-07)
; ; ; ; ;Bai, L.; Earth and Planetary Sciences, McGill University, Montreal, Quebec, Canada ;Baker, D. R.; Earth and Planetary Sciences, McGill University, Montreal, Quebec, Canada ;Polacci, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Hill, R. J.; Department of Chemical Engineering and McGill Institute for Advanced Materials, McGill University, Montreal, Quebec, Canada; ;; Three-dimensional crystal and bubble sizes and distributions in experimentally produced vesicular crystal-bearing Stromboli basalts and natural scoria were studied with X-ray microtomography (μCT) at high (1.85 μm) and low (5.46–9.0 μm) resolution. The permeabilities from lattice Boltzmann (LB) simulations and experimental measurements are about 1–2 orders of magnitude higher than in aphyric Stromboli basalts at porosity 31.6–55.3%. We propose that the higher permeability in crystal-bearing samples results in highly efficient degassing in shallow, highly porphyritc (HP) magma as opposed to the deeper, aphyric (LP) magma. In paroxysmal explosions, the LP magma flows up in a cylindrical conduit due to the density and viscosity difference between the two magmas. This type of convection can cause the LP magma with exsolved gas to be efficiently transferred through the overlying HP magma, potentially resulting in the more-violent paroxysmal explosions.150 37 - PublicationRestrictedAn introduction to the application of X-ray microtomography to the three-dimensional study of igneous rocks(2012-09-01)
; ; ; ; ; ; ; ;Baker, D. R.; Earth and Planetary Sciences, McGill University, 3450 rue University, Montreal, Canada ;Mancini, L.; Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5, 34149 Basovizza (TS), Italy ;Polacci, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Higgins, M. D.; Sciences de la Terre, Université du Québec à Chicoutimi, Chicoutimi, Canada ;Gualda, G. A. R.; Vanderbilt University, Earth and Environmental Sciences, Nashville, TN 37235, USA ;Hill, R. J.; Chemical Engineering and McGill Institute for Advanced Materials, McGill University, Montreal, Canada ;Rivers, M. L.; GSECARS and Department of Geophysical Sciences, University of Chicago, IL 60439, USA ;; ; ; ; ; Imaging rocks in three-dimensions through X-ray microtomography enables routine visualization of structures in samples, which can be spatially resolved down to the sub-micron scale. Although X-ray tomography has been applied in biomedical research and clinical settings for decades, it has only recently been applied to studies of rocks, and few geoscientists realize its value and potential. This contribution provides an introduction to the principles and techniques of X-ray microtomography to the study of igneous rock textures as well as reviewing the current state of the art. We hope that this short review will encourage more geoscientists to apply X-ray microtomography in their research and that this will lead to new insights into the processes that occur in magmatic (as well as other geological) systems.112 19 - PublicationRestrictedVesiculation in magmas from Stromboli and implications for normal Strombolian activity and paroxysmal explosions in basaltic systems(2009-01-30)
; ; ; ; ; ;Polacci, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Baker, D. R.; Earth and Planetary Sciences, McGill University, Montreal, Quebec, Canada ;Mancini, L.; SYRMEP Group, Basovizza, Italy ;Favretto, S.; Dipartimento Materiali e Risorse Naturali, Università di Trieste,Trieste, Italy ;Hill, R.; Department of Chemical Engineering, McGill University, Montreal, Quebec, Canada; ;; ; We performed a series of X-ray tomographic experiments and lattice Boltzmann permeability simulations on pyroclastic products from explosive activity at Stromboli between December 2004 and May 2006. We reconstructed the 3-D textures of vesicles to investigate the relationship between the nature of vesiculation in the erupted products and the dynamics of gas transport in the shallow conduit in order to derive implications for the eruptive behavior of basaltic volcanoes. Scoriae from normal Strombolian explosions display remarkably consistent vesicle volume distributions fit by power laws with an exponent of 1 (±0.2). We ascribe the origin of such distributions to the combined effect of coalescence and continuous nucleation events in the steady state, shallow magma system that supplies normal Strombolian activity. Volume distributions and textures of vesicles in pumice clasts from the 5 April 2003 and 15 March 2007 paroxysmal activity are markedly different from those in the scoriae. Besides a power law function with a higher exponent, portions of these distributions can be also fit by an exponential function, suggesting the attempt of the system to reach near-equilibrium conditions. The investigated pumice clasts also lack the large, connecting vesicles responsible for the development of degassing pathways in the Stromboli magma that erupts the scoriae. This testifies to a decreased degassing efficiency of the magma associated with paroxysmal explosions and potential overpressure buildup at depth. By comparison with degassing experiments on basaltic melts, we derive a time constraint on the order of minutes to hours for the incubation of paroxysms at Stromboli.114 15