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Campi Flegrei Deep Drilling Project (CFDDP): Rheology and physical properties of feldspar- and bubble-bearing andesite and trachyte magmas

English title Campi Flegrei Deep Drilling Project (CFDDP): Rheology and physical properties of feldspar- and bubble-bearing andesite and trachyte magmasrties of intermediate composition plagioclase- and bubble-bearing magmas
Applicant Ulmer Peter
Number 135464
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geochemie und Petrologie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geology
Start/End 01.04.2011 - 31.03.2012
Approved amount 63'804.00
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All Disciplines (2)

Discipline
Geology
Geophysics

Lay Summary (English)

Lead
Lay summary

roject (CFDDP, ICDP-04/07), an ICDP (International Continental Scientific Drilling Program) initiative that starts operation in 2011 with a 500m deep pilot hole to investigate the volcanic substructure and source mechanism of caldera unrest in the Gulf of Naples area. The Rock Deformation laboratory of ETH Zurich is one of the partner institutions leading this project particularly focusing on rock mechanics, rheology and elastic properties of volcanic rocks building up the edifice of the Campi Flegrei Caldera system drilled in the course of the project. This project focuses on two subjects: (1) Basic experimental research targeting the rheologic and elastic behavior and properties of intermediate composition (andesitic to trachytic) magmas containing both feldspar crystals and vapor bubbles, and (2) a rock deformation/petrophysics study conducted directly on recovered volcanic rocks from the CFDDP drill hole to characterize the mechanical and elastic properties of these rocks and to test and apply our results obtained from the experimental investigation of synthetic analogues.Prilling Deep Dlegrei Fampi CThis PhD project is related to the

Intermediate composition supra-subduction volcanoes span a wide range of eruptive style, from relatively benign effusive flows to devastating explosive Plinian eruptions. This dynamic variety of volcanic activities is a direct consequence of both the underground driving forces and the magma rheological properties. To quantify this phenomenon, this study experimentally investigates the mechanical properties of crystal and bubble-bearing magmas focusing on the poorly constrained andesite and trachyte compositions using a Paterson-type internally-heated gas-pressure apparatus. The viscosity, shear strength, and elastic parameters shall be characterized over a broad range of extrinsic conditions (temperature, confining pressure and differential stress) and intrinsic rock properties (crystal fraction, bubble fraction and melt composition) relevant for crystal-rich, evolved magma compositions.

The first part of the study consists of a rock-deformation investigation employing plagioclase, the predominant crystal phase in andesite and trachyte. This enables us to quantify crystal-related effects on magma rheology such as crystal shape and crystal strength. Systematic modification of the liquid composition with increasing crystal fraction takes into account the effect of progressive crystallization. Experiments on bubble-bearing samples are performed to constrain their impact on magma rheology. These experiments will provide the basis for realistic flow laws for a given melt-crystal-bubble relationship. The investigation of the ductile–brittle transition will be achieved by approaching the critical relaxation state by two different ways: (1) by lowering the temperature and (2) by increasing the strain rate. Throughout all experiments, Acoustic Emission (AE) monitoring will be employed to determine the switch from ductile to brittle and vice versa, as well as monitoring decompression effects (i.e. bubble growth, bubble coalescence and degassing) during experiments on the bubble bearing samples.

relationships and acoustic emissions connected to the observed brittle/ductile transitions in the investigated area. The data set acquired in this study is fundamental to understand and model the dynamics of shallow level magma reservoirs, and to better constrain ascent mechanisms, probability and style of eruption, and finally assess the potential hazards of volcanic areas to the surrounding populations.S/VPThe second part of the project is dedicated to complementary petrophysical laboratory measurements on natural, cored samples provided by the CFDDP to confirm the relevance of our experimental results and to constrain geophysical data acquired in the course of the deep drilling project in particular V

Keywords: Campi Flegrei Deep Drilling Project, magma rheology, experimental rock deformation, elastic properties, andesite and trachyte systems, crystal- and bubble-bearing magmas, volcanic eruption dynamics

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Depositional characteristics and volcanic landforms in the Lake Natron – Engaruka monogenetic field, northern Tanzania
Mattsson Hannes B., Tripoli Barbara A. (2011), Depositional characteristics and volcanic landforms in the Lake Natron – Engaruka monogenetic field, northern Tanzania, in Journal of Volcanology and Geothermal Research, 203, 23-34.

Collaboration

Group / person Country
Types of collaboration
University of Lausanne Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
University of Montpellier France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
EGU Vienna 2012 Talk given at a conference Rheology of Three-Phase Magmas 23.04.2012 Vienna, Austria, Austria Ulmer Peter;
AGU Fall Meeting 2011 Talk given at a conference In-situ ultrafast 3D imaging of magma vesiculation at high temperature 05.12.2011 San Francisco, United States of America Benson Philip M.; Ulmer Peter;
AGU Fall Meeting 2011 Poster The brittle-ductile transition in crystal and bubble-bearing magmas 05.12.2011 San Francisco, USA, United States of America Benson Philip M.; Ulmer Peter; Tripoli Barbara;


Associated projects

Number Title Start Funding scheme
140578 Rheologic, physical and kinetic properties of igneous systems 01.04.2012 Project funding (Div. I-III)

Abstract

This PhD project is directly related to the Campi Flegrei Deep Drilling Project (CFDDP) that just started operation with a 500m deep pilot hole to investigate the volcanic substructure and source mechanism of caldera unrest in the Gulf of Naples area. The Rock Deformation laboratory of ETH Zurich is one of the partner institutions (originally represented by the deceased PD Dr. Luigi Burlini, now by the Co-PI, Prof. Dr. Jean-Pierre Burg) leading this project particularly focusing on rock mechanics, rheology and elastic properties of volcanic rocks building up the edifice of the Campi Flegrei Caldera system drilled in the course of the project. The proposed PhD project focuses on two subjects: (1) Basic experimental research targeting the rheologic and elastic behavior and properties of intermediate composition calc-alkaline (andesitic to trachytic) magmas containing both feldspar crystals and vapor bubbles, and (2) a rock deformation/petrophysics study conducted directly on recovered volcanic rocks from the CFDDP drill hole to characterize the mechanical and elastic properties of these rocks and to test and apply our results obtained from the experimental investigation of synthetic analogues.Intermediate composition supra-subduction volcanoes dominated by andesitic to trachytic compositions span a wide range of eruptive style, from relatively benign effusive flows to devastating explosive Plinian eruptions. This dynamic variety of volcanic activities is a direct consequence of both the underground driving forces and the magma rheological properties. To quantify this phenomenon, we propose a experimental investigation of the mechanical properties of crystal and bubble-bearing magmas focusing on the poorly constrained andesite and trachyte compositions using a Paterson-type internally-heated gas-pressure apparatus. The viscosity, shear strength, and elastic parameters shall be characterized over a broad range of extrinsic conditions (temperature, confining pressure and differential stress) and intrinsic rock properties (crystal fraction, bubble fraction and melt composition) relevant for crystal-rich, evolved magma compositions.The first part of the study consists of a rock-deformation investigation employing plagioclase, the predominant crystal phase in andesite and trachyte, in the synthesis instead of quartz so far investigated in more acidic (rhyolitic) compositions. This enables us to quantify crystal-related effects on magma rheology such as crystal shape and crystal strength. In addition, we will modify the liquid composition with increasing crystal fraction to take into account the effect of progressive crystallization. Experiments on bubble-bearing samples will be performed to constrain their impact on magma rheology. These experiments will provide the basis for realistic flow laws for a given melt-crystal-bubble relationship. The investigation of the ductile-brittle transition will be achieved by approaching the critical relaxation state by two different ways: (1) by lowering the temperature and (2) by increasing the strain rate. Throughout all experiments, Acoustic Emission (AE) monitoring will be employed to determine the switch from ductile to brittle and vice versa, as well as monitoring decompression effects (i.e. bubble growth, bubble coalescence and degassing) during experiments on the bubble bearing samples.The second part of the project is dedicated to complementary petrophysical laboratory measurements on natural, cored samples provided by the Campi Flegrei Deep Drilling Project (CFDDP, ICDP-04/07) in order to confirm the relevance of our experimental results and to constrain geophysical data acquired in the course of the deep drilling project in particular VP/VS relationships and acoustic emissions connected to the observed brittle/ductile transitions in the investigated area. The data set acquired in this study is fundamental to understand and model the dynamics of shallow level magma reservoirs, and to better constrain ascent mechanisms, probability and style of eruption, and finally assess the potential hazards of volcanic areas to the surrounding populations.
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