Experimental Constraints on Plagioclase Crystallization during H2O- and H2O-CO2-Saturated Magma Decompression.
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| Title: | Experimental Constraints on Plagioclase Crystallization during H |
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| Authors: | Riker, Jenny M.1 jenny.riker@bristol.ac.uk, Cashman, Katharine V.1, Rust, Alison C.1, Blundy, Jonathan D.1 |
| Source: | Journal of Petrology. Oct2015, Vol. 56 Issue 10, p1967-1998. 32p. |
| Subjects: | Plagioclase, Crystallization, Magmas, Volcanic ash, tuff, etc., Crystal texture, Degassing of metals |
| Abstract: | Experiments simulating magma decompression allow the textures of volcanic rocks to be calibrated against known eruptive conditions. Interpretation of natural samples may be complicated, however, by both the decompression path and the composition of exsolving volatiles, which affect the time evolution of crystal textures. Here we present the results of decompression experiments at elevated temperature and pressure designed to assess the effects of degassing path on crystallization of Mount St. Helens rhyodacite. Three families of experiments were employed to simulate varied PH2O-t trajectories: single-step, H2O-saturated decompression (SSD); continuous, H2O-saturated decompression (CD); continuous, H2O-CO2-saturated decompression. Quantitative textural data (crystal abundance, number density, and size) are used to calculate plagioclase nucleation and growth rates and assess deviations from equilibrium in run products. These are the first experiments to quantify feldspar nucleation and growth rates during H2O-CO2-saturated decompression. We find that reducing the initial melt water content through addition of CO2 increases nucleation rates relative to the pure water case, an effect most pronounced at low dP/dt. Moreover, these early formed textural distinctions persist at the lowest pressures examined, suggesting that deep H2O-CO2 fluids could leave a lasting textural 'fingerprint' on erupted magmas. Crystals formed prior to decompression during the annealing process also modulate sample textures, and growth on pre-existing crystals contributes significantly to added crystallinity at a wide range of experimental conditions. The phase assemblage itself is a dynamic variable that can be used in conjunction with textural data to infer conditions of magma ascent and eruption. Finally, quantitative textural data from experimental samples are compared with those of natural pyroclasts erupted during the summer 1980 explosive-effusive transition at Mount St. Helens. This comparison supports a model of magma ejected from multiple storage regions present in the upper crust following the May 18 Plinian eruption, such that subsequent eruptions tapped magmas that experienced varied decompression and degassing histories. [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of Petrology is the property of Oxford University Press / USA 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: 111550953 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Experimental Constraints on Plagioclase Crystallization during H<subscript>2</subscript>O- and H<subscript>2</subscript>O-CO<subscript>2</subscript>-Saturated Magma Decompression. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Riker%2C+Jenny+M%2E%22">Riker, Jenny M.</searchLink><relatesTo>1</relatesTo><i> jenny.riker@bristol.ac.uk</i><br /><searchLink fieldCode="AR" term="%22Cashman%2C+Katharine+V%2E%22">Cashman, Katharine V.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Rust%2C+Alison+C%2E%22">Rust, Alison C.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Blundy%2C+Jonathan+D%2E%22">Blundy, Jonathan D.</searchLink><relatesTo>1</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Petrology%22">Journal of Petrology</searchLink>. Oct2015, Vol. 56 Issue 10, p1967-1998. 32p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Plagioclase%22">Plagioclase</searchLink><br /><searchLink fieldCode="DE" term="%22Crystallization%22">Crystallization</searchLink><br /><searchLink fieldCode="DE" term="%22Magmas%22">Magmas</searchLink><br /><searchLink fieldCode="DE" term="%22Volcanic+ash%2C+tuff%2C+etc%2E%22">Volcanic ash, tuff, etc.</searchLink><br /><searchLink fieldCode="DE" term="%22Crystal+texture%22">Crystal texture</searchLink><br /><searchLink fieldCode="DE" term="%22Degassing+of+metals%22">Degassing of metals</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Experiments simulating magma decompression allow the textures of volcanic rocks to be calibrated against known eruptive conditions. Interpretation of natural samples may be complicated, however, by both the decompression path and the composition of exsolving volatiles, which affect the time evolution of crystal textures. Here we present the results of decompression experiments at elevated temperature and pressure designed to assess the effects of degassing path on crystallization of Mount St. Helens rhyodacite. Three families of experiments were employed to simulate varied PH2O-t trajectories: single-step, H2O-saturated decompression (SSD); continuous, H2O-saturated decompression (CD); continuous, H2O-CO2-saturated decompression. Quantitative textural data (crystal abundance, number density, and size) are used to calculate plagioclase nucleation and growth rates and assess deviations from equilibrium in run products. These are the first experiments to quantify feldspar nucleation and growth rates during H2O-CO2-saturated decompression. We find that reducing the initial melt water content through addition of CO2 increases nucleation rates relative to the pure water case, an effect most pronounced at low dP/dt. Moreover, these early formed textural distinctions persist at the lowest pressures examined, suggesting that deep H2O-CO2 fluids could leave a lasting textural 'fingerprint' on erupted magmas. Crystals formed prior to decompression during the annealing process also modulate sample textures, and growth on pre-existing crystals contributes significantly to added crystallinity at a wide range of experimental conditions. The phase assemblage itself is a dynamic variable that can be used in conjunction with textural data to infer conditions of magma ascent and eruption. Finally, quantitative textural data from experimental samples are compared with those of natural pyroclasts erupted during the summer 1980 explosive-effusive transition at Mount St. Helens. This comparison supports a model of magma ejected from multiple storage regions present in the upper crust following the May 18 Plinian eruption, such that subsequent eruptions tapped magmas that experienced varied decompression and degassing histories. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Journal of Petrology is the property of Oxford University Press / USA 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: 10.1093/petrology/egv059 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 32 StartPage: 1967 Subjects: – SubjectFull: Plagioclase Type: general – SubjectFull: Crystallization Type: general – SubjectFull: Magmas Type: general – SubjectFull: Volcanic ash, tuff, etc. Type: general – SubjectFull: Crystal texture Type: general – SubjectFull: Degassing of metals Type: general Titles: – TitleFull: Experimental Constraints on Plagioclase Crystallization during H2O- and H2O-CO2-Saturated Magma Decompression. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Riker, Jenny M. – PersonEntity: Name: NameFull: Cashman, Katharine V. – PersonEntity: Name: NameFull: Rust, Alison C. – PersonEntity: Name: NameFull: Blundy, Jonathan D. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 10 Text: Oct2015 Type: published Y: 2015 Identifiers: – Type: issn-print Value: 00223530 Numbering: – Type: volume Value: 56 – Type: issue Value: 10 Titles: – TitleFull: Journal of Petrology Type: main |
| ResultId | 1 |
