Permeability of vesicular silicic magma: inertial and hysteresis effects
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| Title: | Permeability of vesicular silicic magma: inertial and hysteresis effects |
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| Authors: | Rust, A.C.1 arust@eos.ubc.ca, Cashman, K.V.2 cashman@uoregon.edu |
| Source: | Earth & Planetary Science Letters. Nov2004, Vol. 228 Issue 1/2, p93-107. 15p. |
| Subjects: | Magmas, Volcanoes, Porosity, Igneous rocks |
| Abstract: | Abstract: The permeability of crystal-poor obsidian flow and pumice samples from Medicine Lake Volcano, USA, are measured to assess (1) the existence of a critical vesicularity (porosity) below which low crystallinity magma is effectively impermeable, (2) the effects of bubble texture on permeability, and (3) the importance of inertial effects in resisting fluid flow through magma. Consistent with prior studies, the Medicine Lake data indicate that fluids can readily percolate through magma with porosities greater than 65%. However, we find no abrupt decrease in permeability below 60% porosity, as found previously for low crystallinity samples of similar origin from Obsidian Dome, USA. Rather, the permeabilities of Medicine Lake samples show a gradual increase with increased vesicularity similar to that observed in highly crystalline samples from Soufriere Hills Volcano, Montserrat, and Mount Saint Helens, USA. We suggest that both vesicle microstructure and resulting porosity–permeability relationships depend on the deformation, decompression and degassing history of the magma. In particular, bubble deformation by shear and/or partial bubble collapse allows open-system degassing of magma with vesicularity of 20%, and perhaps lower. Permeability determines the rate at which samples can degas during decompression. Air flow rates through lava and pumice samples are not proportional to the pressure gradients driving flow, indicating that inertial effects are significant at laboratory conditions. Flow resistance from both inertial and viscous effects generally decreases with increasing porosity, and inertial effects are smaller for coarsely vesicular lava than for finely vesicular lava or pumice (tephra) samples with similar viscous (Darcian) permeabilities. For an H2O fluid at 800 °C and 25 MPa, the critical average fluid speed at which inertial and viscous effects are predicted to be comparable is between 10−4 and 10−1 m/s for all the Medicine Lake samples. As flow rates in this range are anticipated for volcanic eruption conditions, inertial effects should be considered in models of magma degassing at depth. [Copyright &y& Elsevier] |
| Copyright of Earth & Planetary Science Letters is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
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| Header | DbId: egs DbLabel: Engineering Source An: 15426222 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Permeability of vesicular silicic magma: inertial and hysteresis effects – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Rust%2C+A%2EC%2E%22">Rust, A.C.</searchLink><relatesTo>1</relatesTo><i> arust@eos.ubc.ca</i><br /><searchLink fieldCode="AR" term="%22Cashman%2C+K%2EV%2E%22">Cashman, K.V.</searchLink><relatesTo>2</relatesTo><i> cashman@uoregon.edu</i> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Earth+%26+Planetary+Science+Letters%22">Earth & Planetary Science Letters</searchLink>. Nov2004, Vol. 228 Issue 1/2, p93-107. 15p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Magmas%22">Magmas</searchLink><br /><searchLink fieldCode="DE" term="%22Volcanoes%22">Volcanoes</searchLink><br /><searchLink fieldCode="DE" term="%22Porosity%22">Porosity</searchLink><br /><searchLink fieldCode="DE" term="%22Igneous+rocks%22">Igneous rocks</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Abstract: The permeability of crystal-poor obsidian flow and pumice samples from Medicine Lake Volcano, USA, are measured to assess (1) the existence of a critical vesicularity (porosity) below which low crystallinity magma is effectively impermeable, (2) the effects of bubble texture on permeability, and (3) the importance of inertial effects in resisting fluid flow through magma. Consistent with prior studies, the Medicine Lake data indicate that fluids can readily percolate through magma with porosities greater than 65%. However, we find no abrupt decrease in permeability below 60% porosity, as found previously for low crystallinity samples of similar origin from Obsidian Dome, USA. Rather, the permeabilities of Medicine Lake samples show a gradual increase with increased vesicularity similar to that observed in highly crystalline samples from Soufriere Hills Volcano, Montserrat, and Mount Saint Helens, USA. We suggest that both vesicle microstructure and resulting porosity–permeability relationships depend on the deformation, decompression and degassing history of the magma. In particular, bubble deformation by shear and/or partial bubble collapse allows open-system degassing of magma with vesicularity of 20%, and perhaps lower. Permeability determines the rate at which samples can degas during decompression. Air flow rates through lava and pumice samples are not proportional to the pressure gradients driving flow, indicating that inertial effects are significant at laboratory conditions. Flow resistance from both inertial and viscous effects generally decreases with increasing porosity, and inertial effects are smaller for coarsely vesicular lava than for finely vesicular lava or pumice (tephra) samples with similar viscous (Darcian) permeabilities. For an H2O fluid at 800 °C and 25 MPa, the critical average fluid speed at which inertial and viscous effects are predicted to be comparable is between 10−4 and 10−1 m/s for all the Medicine Lake samples. As flow rates in this range are anticipated for volcanic eruption conditions, inertial effects should be considered in models of magma degassing at depth. [Copyright &y& Elsevier] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Earth & Planetary Science Letters is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1016/j.epsl.2004.09.025 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 15 StartPage: 93 Subjects: – SubjectFull: Magmas Type: general – SubjectFull: Volcanoes Type: general – SubjectFull: Porosity Type: general – SubjectFull: Igneous rocks Type: general Titles: – TitleFull: Permeability of vesicular silicic magma: inertial and hysteresis effects Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Rust, A.C. – PersonEntity: Name: NameFull: Cashman, K.V. IsPartOfRelationships: – BibEntity: Dates: – D: 30 M: 11 Text: Nov2004 Type: published Y: 2004 Identifiers: – Type: issn-print Value: 0012821X Numbering: – Type: volume Value: 228 – Type: issue Value: 1/2 Titles: – TitleFull: Earth & Planetary Science Letters Type: main |
| ResultId | 1 |
