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Eruptive shearing of tube pumice: Pure and simple
- Source :
- Digital.CSIC. Repositorio Institucional del CSIC, instname, SOLID EARTH, Solid Earth, Vol 7, Iss 5, Pp 1383-1393 (2016)
- Publication Year :
- 2016
- Publisher :
- European Geosciences Union, 2016.
-
Abstract
- Understanding the physicochemical conditions extant and mechanisms operative during explosive volcanism is essential for reliable forecasting and mitigation of volcanic events. Rhyolitic pumices reflect highly vesiculated magma whose bubbles can serve as a strain indicator for inferring the state of stress operative immediately prior to eruptive fragmentation. Obtaining the full kinematic picture reflected in bubble population geometry has been extremely difficult, involving dissection of a small number of delicate samples. The advent of reliable high-resolution tomography has changed this situation radically. Here we demonstrate via the use of tomography how a statistically powerful picture of the shapes and connectivity of thousands of individual bubbles within a single sample of tube pumice emerges. The strain record of tube pumice is modelled using empirical models of bubble geometry and liquid rheology, reliant on a constraint of magmatic water concentration. FTIR analysis reveals an imbalance in water speciation, suggesting post-eruption hydration, further supported by hydrogen and oxygen isotope measurements. Our work demonstrates that the strain recorded in the tube pumice dominated by simple shear (not pure shear) in the late deformational history of vesicular magma before eruption. This constraint in turn implies that magma ascent is conditioned by a velocity gradient (across the conduit) at the point of origin of tube pumice. Magma ascent accompanied by simple shear should enhance high eruption rates inferred independently for these highly viscous systems. © Author(s) 2016.<br />Financial support was provided by the Deutsche Forschungsgemeinschaft (DFG) – International Continental Drilling Program (ICDP) grant HE 4565-2-1 as well as the DFG grants LA 2651-1-1 and LA 2651 3-1. Yan Lavallée acknowledges support from the European Research Council (ERC) for the Starting Grant on Strain Localisation in Magmas (SLiM, no. 306488). Donald B. Dingwell acknowledges a Research Professorship in Experimental Volcanology of the Bundesexzellenzinitiative (LMUexcellent) as well as an ERC Advanced Grant on Explosive Volcanism in the Earth System (EVOKES, no. 247076).
- Subjects :
- 010504 meteorology & atmospheric sciences
Stratigraphy
Population
Tubes (components)
Soil Science
Mineralogy
Volcanism
010502 geochemistry & geophysics
01 natural sciences
Magmatic water
lcsh:Stratigraphy
Geochemistry and Petrology
Empirical model
Pumice
education
Tomography
Explosive volcanism
Viscous systems
lcsh:QE640-699
Earth-Surface Processes
0105 earth and related environmental sciences
Shearing (physics)
geography
education.field_of_study
geography.geographical_feature_category
lcsh:QE1-996.5
Paleontology
Geology
Pure shear
Strain indicators
lcsh:Geology
Simple shear
Bubble Geometry
Geophysics
Volcano
High-resolution tomography
Velocity gradients
Physicochemical conditions
Subjects
Details
- Database :
- OpenAIRE
- Journal :
- Digital.CSIC. Repositorio Institucional del CSIC, instname, SOLID EARTH, Solid Earth, Vol 7, Iss 5, Pp 1383-1393 (2016)
- Accession number :
- edsair.doi.dedup.....ed6ac81073058b6fff25723c4f117f8b