The role of fluidisation in the formation of volcaniclastic kimberlite: Grain size observations and experimental investigation

Walters, AL; Phillips, Jeremy C.; Brown, R. J. K.; Field, M. Paul; Gernon, Thomas M.; Stripp, G.; Sparks, R. S. J.

doi:10.1016/j.jvolgeores.2006.02.005

Cited by 82 publications

(72 citation statements)

References 33 publications

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“…Our experiments address individual explosions; they are not intended to be representative of entire volcano-forming events, or even entire eruptions. Fluidization experiments last orders of magnitude longer than our injections (seconds to minutes vs. <1 s), but are shorter by similar orders of magnitude than observed maarforming eruptions inferred to have produced diatremes (Müller and Veyl 1957;Woolsey et al 1975;Self et al 1980;Walters et al 2006). Deposits -It is not possible to compare deposits from our experiments with those of fluidization experiments because the latter involve only gas and host materials.…”

Section: Discussionmentioning

confidence: 66%

“…This method differs considerably from fluidization experiments (e.g., Woolsey et al 1975;Wilson 1980;Nichols et al 1994;Walters et al 2006) in which compressed gas or water -without any suspended particles -is injected from the base of a container at a constant fluid velocity for several seconds or minutes, leading to quasi steady-state conditions. Such experiments do not model the process we want to investigate (transient debris jets above explosion sites), hence the need for a new type of setup.…”

Section: Methodsmentioning

confidence: 99%

“…We do not assume that the vent fills of interest are fluidized between eruptive pulses (cf. Woolsey et al 1975;Kokelaar 1983;Walters et al 2006) so we model the rapid injection of particles and gas into static, non-fluidized granular material.…”

Section: Introductionmentioning

confidence: 99%

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Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications

et al. 2008

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In diatremes and other volcanic vents, steep bodies of volcaniclastic material having differing properties (particle size distribution, proportion of lithic fragments, etc.) from those of the surrounding vent-filling volcaniclastic material are often found. It has been proposed that cylindrical or cone-shaped bodies result from the passage of "debris jets" generated after phreatomagmatic explosions or other discrete subterranean bursts. To learn more about such phenomena, we model experimentally the injection of gas-particulate dispersions through other particles. Analogue materials (glass beads or sand) and a finite amount of compressed air are used in the laboratory. The gas is made available by rapidly opening a valvetherefore the injection of gas and coloured particles into a granular host is a brief (<1 s), discrete event, comparable to what occurs in nature following subterranean explosions. The injection assumes a bubble shape while expanding and propagating upwards. In reaction, the upper part of the clastic host moves upward and outward above the 'bubble', forming a 'dome'. The doming effect is much more pronounced for shallow injection depths (thin hosts), with dome angles reaching more than 45°. Significant surface doming is also observed for some full-scale subterranean blasts (e.g. buried nuclear explosions), so it is not an artefact of our setup. What happens next in the experiments depends on the depth of injection and the nature of the host material. With shallow injection into a permeable host (glass beads), the compressed air in the "bubble' is able to diffuse rapidly through the roof. Meanwhile the coloured beads sediment into the transient cavity, which is also closing laterally because of inward-directed granular flow of the host. Depending on the initial gas pressure in the reservoir, the two-phase flow can "erupt" or not; non-erupting injections produce cylindrical bodies of coloured beads whereas erupting runs produce flaring upward or conical deposits. Changing the particle size of the host glass beads does not have a large effect under the size range investigated (100-200 to 300-400 µm). Doubling the host thickness (injection depth) requires a doubling of the initial gas pressure to produce similar phenomena. Such injections -whether erupting or wholly subterranean -provide a compelling explanation for the origin and characteristics of multiple cross-cutting bodies that have been documented for diatreme and other vent deposits.

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Section: Discussionmentioning

confidence: 66%

Section: Methodsmentioning

confidence: 99%

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Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications

et al. 2008

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“…Both particles and gas, rather than only gas or water, are injected at the base of the container. Steady state fluidization experiments (e.g., Woolsey et al, 1975;Walters et al, 2006) do not reproduce discrete, explosive injections of entrained particles through a particulate host, which is the phenomenon we wished to study.…”

Section: Methodsmentioning

confidence: 99%

Multiphase flow above explosion sites in debris-filled volcanic vents: Insights from analogue experiments

Ross

White

Zimanowski

et al. 2008

Journal of Volcanology and Geothermal Research

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Discrete explosive bursts are known from many volcanic eruptions. In maar-diatreme eruptions, they have occurred in debris-filled volcanic vents when magma interacted with groundwater, implying that material mobilized by such explosions passed through the overlying and enclosing debris to reach the surface. Although other studies have addressed the form and characteristics of craters formed by discrete explosions in unconsolidated material, no details are available regarding the structure of the disturbed debris between the explosion site and the surface. Field studies of diatreme deposits reveal cross-cutting, steep-sided zones of non-bedded volcaniclastic material that have been inferred to result from sedimentation of material transported by "debris jets" driven by explosions. In order to determine the general processes and deposit geometry resulting from discrete, explosive injections of entrained particles through a particulate host, we ran a series of analogue experiments. Specific volumes of compressed (0.5-2.5 MPa) air were released in bursts that drove gas-particle dispersions through a granular host. The air expanded into and entrained coloured particles in a small crucible before moving upward into the host (white particles). Each burst drove into the host an expanding cavity containing air and coloured particles. Total duration of each run, recorded with high-speed video, was approximately 0.5-1 second. The coloured beads sedimented into the transient cavity. This same behaviour was observed even in runs where there was no breaching of the surface, and no coloured beads ejected. A steep-sided body of coloured beads was left that is similar to the cross-cutting pipes observed in deposits filling real volcanic vents, in which cavity collapse can result not only from gas escape through a granular host as in the experiments, but also through condensation of water vapour. A key conclusion from these experiments is that the geometry of cross-cutting volcaniclastic deposits in volcanic vents is not directly informative of the geometry of the "intrusions" that formed them. An additional conclusion is that complex structures can form quickly from discrete events.

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“…Diatremes "store" potentially the most valuable information on how the magma and water interacted and how the resulting fragmented rocks are transported away from their fragmentation site to the deposition sites surrounding the craters. The mode of transportation of pyroclast from the explosion site is much under debate and involves various processes generating fluidisation, debris jet formation and various vertically moving pyroclastic density current activities [78,[172][173][174][175][176][177].…”

Section: Intrusive Forms Related To Na-alkalic and Ultrapotassic Rocksmentioning

confidence: 99%

Neogene-Quaternary Volcanic forms in the Carpathian-Pannonian Region: a review

et al. 2010

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Neogene to Quaternary volcanic/magmatic activity in the Carpathian-Pannonian Region (CPR) occurred between 21 and 0.1 Ma with a distinct migration in time from west to east. It shows a diverse compositional variation in response to a complex interplay of subduction with roll-back, back-arc extension, collision, slab break-off, delamination, strike-slip tectonics and microplate rotations, as well as in response to further evolution of magmas in the crustal environment by processes of differentiation, crustal contamination, anatexis and magma mixing. Since most of the primary volcanic forms have been affected by erosion, especially in areas of post-volcanic uplift, based on the level of erosion we distinguish: (1) areas eroded to the basement level, where paleovolcanic reconstruction is not possible; (2) deeply eroded volcanic forms with secondary morphology and possible paleovolcanic reconstruction; (3) eroded volcanic forms with remnants of original morphology preserved; and (4) the least eroded volcanic forms with original morphology quite well preserved. The large variety of volcanic forms present in the area can be grouped in a) monogenetic volcanoes and b) polygenetic volcanoes and their subsurface/intrusive counterparts that belong to various rock series found in the CPR such as calc-alkaline magmatic rock-types (felsic, intermediate and mafic varieties) and alkalic types including K-alkalic, shoshonitic, ultrapotassic and Na-alkalic. The following volcanic/subvolcanic forms have been identified: (i) domes, shield volcanoes, effusive cones, pyroclastic cones, stratovolcanoes and calderas with associated intrusive bodies for intermediate and basic calc-alkaline volcanism; (ii) domes, calderas and ignimbrite/ash-flow fields for felsic calc-alkaline volcanism and (iii) dome flows, shield volcanoes, maars, tuffcone/tuff-rings, scoria-cones with or without related lava flow/field and their erosional or subsurface forms (necks/ plugs, dykes, shallow intrusions, diatreme, lava lake) for various types of K-and Na-alkalic and ultrapotassic magmatism. Finally, we provide a summary of the eruptive history and distribution of volcanic forms in the CPR using several sub-region schemes.

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The role of fluidisation in the formation of volcaniclastic kimberlite: Grain size observations and experimental investigation

Cited by 82 publications

References 33 publications

Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications

Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications

Multiphase flow above explosion sites in debris-filled volcanic vents: Insights from analogue experiments

Neogene-Quaternary Volcanic forms in the Carpathian-Pannonian Region: a review

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