Time scales of compaction in volcanic systems

Quane, Steven L.; Russell, James K.; Friedlander, Elizabeth

doi:10.1130/g25625a.1

Cited by 62 publications

(60 citation statements)

References 21 publications

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“…The case of water resorption is possible where τ gas > τ d and τ cooling > τ compaction (lowermost right-hand fi eld of Fig. 13) and may enhance the welding process (Quane et al, 2009;Kamata et al, 1993;Riehle et al, 1995;Buesch and Riehle, 2007). Where τ compaction >> τ d and τ cooling > τ compaction (also in lower right-hand fi eld of Fig.…”

Section: Geometry Of Gas Escapementioning

confidence: 96%

Compaction and gas loss in welded pyroclastic deposits as revealed by porosity, permeability, and electrical conductivity measurements of the Shevlin Park Tuff

Wright

Cashman

2013

Geological Society of America Bulletin

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Pyroclastic fl ows produced by large volcanic eruptions commonly densify after emplacement. Processes of gas escape, compaction, and welding in pyroclastic-fl ow deposits are controlled by the physical and thermal properties of constituent material. Through measurements of matrix porosity, permeability, and electrical conductivity, we provide a framework for understanding the evolution of pore structure during these processes. Using data from the Shevlin Park Tuff in central Oregon, United States, and from the literature, we fi nd that over a porosity range of 0%-70%, matrix permeability varies by almost 10 orders of magnitude (from 10 -20 to 10 -11 m 2 ), with over three orders of magnitude variation at any given porosity. Part of the variation at a given porosity is due to permeability anisotropy, where oriented core samples indicate higher permeabilities parallel to foliation (horizontally) than perpendicular to foliation (vertically). This suggests that pore space is fl attened during compaction, creating anisotropic crack-like networks, a geometry that is supported by electrical conductivity measurements. We fi nd that the power law equation: k 1 = 1.3 × 10 -21 × ϕ 5.2 provides the best approximation of dominant horizontal gas loss, where k 1 = permeability, and ϕ = porosity. Application of Kozeny-Carman fl uid-fl ow approximations suggests that permeability in the Shevlin Park Tuff is controlled by crack-or disklike pore apertures with minimum widths of 0.3 and 7.5 μm. We fi nd that matrix permeability limits compaction over short times, but deformation is then controlled by competition among cooling, compaction, water resorption, and permeable gas escape. These competing processes control the potential for development of overpressure (and secondary explosions) and the degree of welding in the deposit, processes that are applicable to viscous densifi cation of volcanic deposits in general. Further, the general relationships among porosity, permeability, and pore geometry are relevant for fl ow of any fl uid through an ignimbritic host.

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Section: Geometry Of Gas Escapementioning

confidence: 96%

Compaction and gas loss in welded pyroclastic deposits as revealed by porosity, permeability, and electrical conductivity measurements of the Shevlin Park Tuff

Wright

Cashman

2013

Geological Society of America Bulletin

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“…In addition, the upwards increase in crystallinity may introduce a yield strength that lengthens the relaxation time (Giordano et al 2005). Recent experimental work by Quane et al (2009) suggests that welding is independent of cooling rate and is instead dependent upon the depositional process. Welding timescales of experimentally deformed ash cores approach depositional timescales (minutes to hours; Quane et al 2009).…”

Section: Densificationmentioning

confidence: 96%

“…Recent experimental work by Quane et al (2009) suggests that welding is independent of cooling rate and is instead dependent upon the depositional process. Welding timescales of experimentally deformed ash cores approach depositional timescales (minutes to hours; Quane et al 2009). The results of these experiments imply that welding stops while the material is still above the glass transition temperature.…”

Section: Densificationmentioning

confidence: 98%

Columnar jointing in vapor-phase-altered, non-welded Cerro Galán Ignimbrite, Paycuqui, Argentina

et al. 2011

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Columnar jointing is thought to occur primarily in lavas and welded pyroclastic flow deposits. However, the non-welded Cerro Galán Ignimbrite at Paycuqui, Argentina, contains well-developed columnar joints that are instead due to high-temperature vapor-phase alteration of the deposit, where devitrification and vapor-phase crystallization have increased the density and cohesion of the upper half of the section. Thermal remanent magnetization analyses of entrained lithic clasts indicate high emplacement temperatures, above 630°C, but the lack of welding textures indicates temperatures below the glass transition temperature. In order to remain below the glass transition at 630°C, the minimum cooling rate prior to deposition was 3.0×10 −3 -8.5×10 −2°C /min (depending on the experimental data used for comparison). Alternatively, if the deposit was emplaced above the glass transition temperature, conductive cooling alone was insufficient to prevent welding. Crack patterns (average, 4.5 sides to each polygon) and column diameters (average, 75 cm) are consistent with relatively rapid cooling, where advective heat loss due to vapor fluxing increases cooling over simple conductive heat transfer. The presence of regularly spaced, complex radiating joint patterns is consistent with fumarolic gas rise, where volatiles originated in the valley-confined drainage system below. Joint spacing is a proxy for cooling rates and is controlled by depositional thickness/valley width. We suggest that the formation of joints in high-temperature, non-welded deposits is aided by the presence of underlying external water, where vapor transfer causes crystallization in pore spaces, densifies the deposit, and helps prevent welding.

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“…Scott and Kilgour 1969). For more common rhyolitic ignimbrites, the high porosity of the pyroclasts allows for values of total volumetric strain that are at least double (Quane et al 2009). Both the lower volumetric strain and extremely equant grain shape population of kimberlites decreases the visibility of the compaction and pore space reduction that accompany welding or hot pressing.…”

Section: Theoretical Constraintsmentioning

confidence: 95%

A rare occurrence of a crater-filling clastogenic extrusive coherent kimberlite, Victor Northwest (Ontario, Canada)

et al. 2011

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Kimberlite pipes can contain significant proportions of dark and dense kimberlite that have mostly been interpreted as intrusive coherent (hypabyssal) in origin. This study reports a well-documented occurrence of a fresh intra-crater clastogenic extrusive coherent kimberlite that is concluded to have formed as a result of lava fountaining. This paper focuses on a dark, dense, competent, generally crystal-rich, massive kimberlite unit within the Victor Northwest kimberlite pipe (Ontario, Canada). Using a comprehensive volcanological and petrographic analysis of all available drill cores, it is shown that this unit has a fresh well-crystallised coherent groundmass and is extrusive and pyroclastic in origin. The proposed clastogenic coherent extrusive origin is based on deposit morphology, gradational contacts to enveloping pyroclastic units, as well as the presence of remnant pyroclast outlines and angular broken olivines. This paper, and an increasing number of other studies, suggest that fragmental extrusive coherent kimberlite in intra-crater settings may be more common than previously thought. The emplacement history and volcanology of these pipes need to be reconsidered based on the emerging importance of this particular kimberlite facies.

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Time scales of compaction in volcanic systems

Cited by 62 publications

References 21 publications

Compaction and gas loss in welded pyroclastic deposits as revealed by porosity, permeability, and electrical conductivity measurements of the Shevlin Park Tuff

Compaction and gas loss in welded pyroclastic deposits as revealed by porosity, permeability, and electrical conductivity measurements of the Shevlin Park Tuff

Columnar jointing in vapor-phase-altered, non-welded Cerro Galán Ignimbrite, Paycuqui, Argentina

A rare occurrence of a crater-filling clastogenic extrusive coherent kimberlite, Victor Northwest (Ontario, Canada)

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