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Physical properties of crystal- and bubble-bearing magmas

English title Physical properties of crystal- and bubble-bearing magmas
Applicant Ulmer Peter
Number 120221
Funding scheme Project funding (Div. I-III)
Research institution Institut für Mineralogie und Petrographie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Other disciplines of Earth Sciences
Start/End 01.04.2008 - 31.08.2010
Approved amount 182'975.00
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All Disciplines (2)

Discipline
Other disciplines of Earth Sciences
Geology

Keywords (15)

EXPERIMENTAL ROCK DERFORMATION; EXPERIMENTAL PETROLOGY; SILICIC MAGMAS; volcanology; RHEOLOGY OF bubble-bearing magmas; VISCOSITY; bubble-bearing magmas; magma rheology; experimental rock deformation; petrology; structural geology; haplogranite system; seismic properties; volcanic magma systems; Lipari

Lay Summary (English)

Lead
Lay summary
LeadThis study targets to quantify rheologic and elastic properties of partially molten, crystal-rich, felsic, hydrous magmas under shallow crustal conditions relevant for high-level magma reservoirs and volcanic conduits with particular emphasis on bubble-bearing, partially molten felsic magma compositions.BackgroundThe knowledge of physical properties of partially molten, crystal-rich, felsic, hydrous magmas under shallow crustal conditions are a prerequisite to understand and model the formation of high-level magma reservoirs such as shallow plutons or sub-volcanic magma chambers and control the behavior of magmatic suspensions in volcanic conduits leading to effusive and/or explosive eruptions of volcanic rocks. This study continues experimental projects initiated in spring 2004 that quantified physical and rheologic properties, in particular viscosity and seismic wave propagation velocities, of partially molten, crystal-rich, felsic, hydrous magmas under shallow crustal conditions. This new study specifically aims at gaining quantitative information on viscosity, strain, differential stress, yield strength, seismic wave propagation velocities and acoustic emissions of bubble-bearing, partially molten H2O-rich, felsic magma compositions in a combined approach using experimental petrology / rock deformation studies as well as limited field-based petrological and structural geology studies to extract crucial properties under conditions relevant for subsurficial high-level magma storage to surficial extrusion of magmas as lava (effusive) or tephra (explosive). Such data are urgently required to understand and model the dynamics of magma extraction from larger magma reservoirs and their ascend in volcanic conduits, to interpret the complex petrologic and structural patterns observed in shallow-level intermediate to acidic granitoid plutons, their extrusive and explosive volcanic counterparts and to put constraints on the probability and style of volcanic eruptions from such magma reservoirs. Scientific MethodsThis project bases to a large extend on experimental rock deformation (creep) and seismic velocity measurements conducted on fully and partially molten, bubble-bearing felsic compositions (haplogranite in the Na2O-K2O-Al2O3-SiO2-H2O system) employing a gas-pressure rock-deformation apparatus at pressures ranging from 30 to 200 MPa and temperatures varying from 400 to 1100°C. Limited field work that will be conducted on highly viscous magmas ranging from nearly completely degassed crystal-poor to crystal-rich rhyolite and latite to highly vesicular pumices on the island of Lipari shall supplement additional rheological information on acidic volcanics ranging in extrusion mechanism from highly viscous lava flows, to plug extrusion to explosive sub-Plinian eruptions and serve to test and apply experimental data, in particular macro- and microstructural findings, directly to a natural volcanic system with similar compositions.Targets and Significance of the projectThis project, combining dominantly experimental with limited field-based data, will provide a set of quantitative data on the rheologic and elastic properties of partly crystallized, bubble-bearing magmas that are directly relevant for processes operating in sub-volcanic magma reservoirs and extrusion via ascent in a volcanic conduit by laminar flow and by shearing (e.g. in during lava dome extrusion and growth). Extension into the range of Non-Newtonian behavior (high stress, high strain-rate experiments at low temperatures) will enable us to access aspects of magma fragmentation / flow partitioning into narrow shear zones of partially crystallized, bubble-bearing igneous systems. These data will ultimately lead to a considerable improvement of the modeling of complex dynamic magma systems containing vapor-saturated, crystal-rich magma. Direct measurements of compressional and shear wave propagation velocities of vapor-oversaturated, partially molten systems (magmas) provide fundamental information for the identification of such reservoirs and under active and seemingly dormant volcanoes and will help to constrain the physical state (crystallinity, bubble-content) of these potentially hazardous materials. This should not only enable seismologist to identify potentially dangerous magma reservoirs, but also monitoring the changes in these parameters, in particular vp/vs and attenuation could provide a hazard assessment tool to predict imminent violent eruptions of a volcanic system if the dependencies of these parameters can be linked to the physical state of the magmas via an experimental calibration.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
132878 Physical properties of crystal- and bubble-bearing magmas 01.10.2010 Project funding (Div. I-III)
132878 Physical properties of crystal- and bubble-bearing magmas 01.10.2010 Project funding (Div. I-III)
111852 Physical properties of silicic magmas in sub-volcanic magma reservoirs 01.04.2006 Project funding (Div. I-III)

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