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Three-dimensional numerical modelling of fluid generation atop the subducting slab beneath southern Alaska

English title Three-dimensional numerical modelling of fluid generation atop the subducting slab beneath southern Alaska
Applicant Tackley Paul
Number 138209
Funding scheme Project funding
Research institution Institut für Geophysik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geophysics
Start/End 01.10.2011 - 31.03.2013
Approved amount 174'515.00
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Keywords (4)

subduction; volcanism; magmatism; numerical modelling

Lay Summary (English)

Lead
Lay summary

Subduction zones are one of the most important tectonic environments on our planet, with much volcanism occuring above the subducting slab. In this project we study thermo-chemical structures and mantle flow above the subducting slab, with the goal of understanding the pattern of surface volcanism and crustal growth and seismological observations of these regions. This investigation is performed using numerical models. A key feature of our models is three-dimensionality (3-D), which is important because the structures that occur in nature are three-dimensional. This research builds on our 3-D petrological-thermomechanical models funded by  a previous SNF grant, which showed that 3-D thermal-chemical convection patterns (and hence melt productivity distribution) in intra-oceanic subduction zones can be strongly variable and depend on both the magnitude and spatial distribution of chemical buoyancy above slabs. The objective of this new project is to develop a robust 3-D model of oceanic-continental subduction with magma generation and crustal growth, and to achieve a better understanding the fluid/melt generation and propagation atop the subducting slab in the southern Alaskan subduction zone, for which good seismic and petrological information exists. Our 3-D simulations will therefore account for: (i) mantle flow associated with the specific plate convergence rate, (ii) slab water release, (iii) slab fluid propagation that will trigger partial melting at the slab surface, (iv) melt ascent, (vi) variations in density and viscosity of both fluids and rocks as a function of local conditions and (v) relations between melting and melt transport dynamics in 3-D and crustal growth (volcanic activity) at the surface. By comparing with seismic structure and petrological observations in the southern Alaskan subduction zone, we will get a robust oceanic-continental subduction model with well- constrained controlling parameters particularly applicable for this zone. This project funds a postdoctoral scholar for 1.5 years.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Swiss Geoscience Meeting 2012 16.11.2012 Bern, Switzerland
GeoMod 2012 15.07.2012 Lausanne, Switzerland
American Geophysical Union Fall Meeting 05.12.2011 San Francisco, USA
Swiss Geoscience Meeting 2011 11.11.2011 Zürich, Switzerland


Associated projects

Number Title Start Funding scheme
116381 Coupled chemical-thermal-mechanical modelling of magma generation and migration in subduction zones 01.04.2007 Project funding
143299 Crystal2Plate (from crystal-scale processes to mantle convection with self-consistent plates) extension: Influence of fluids on subduction, formation of lithosphere-scale shear zones, and influence of lithospheric heterogeneity on global plate tecton 01.12.2012 Project funding

Abstract

Thermomechanical structures and mantle flows above subducting slabs are likely to be inherently three- dimensional (3-D), as indicated by seismic tomography of mantle wedges and spatial and temporal variability of arc volcanism. Numerical modelling of subduction zones and mantle wedges in 3-D is a rapidly evolving topic, with significant progress during the last decade. However, published 3-D models of subduction are rather rare. Our recent 3-D petrological-thermomechanical models funded by SNF have shown that 3-D thermal-chemical convection patterns (and hence melt productivity distribution) in intra-oceanic subduction zones can be strongly variable and depend on both the magnitude and spatial distribution of chemical buoyancy above slabs. Our existing model of ocean-ocean subduction can be applied to understand volcanism in Japan and New Zealand subduction zones.The objective of this project is to develop a robust 3-D model of oceanic-continental subduction with magma generation and crustal growth, and to achieve a better understanding the fluid/melt generation and propagation atop the subducting slab in the southern Alaskan subduction zone, for which good seismic and petrological information exists. Our 3-D simulations will therefore account for: (i) mantle flow associated with the specific plate convergence rate, (ii) slab water release, (iii) slab fluid propagation that will trigger partial melting at the slab surface, (iv) melt ascent, (vi) variations in density and viscosity of both fluids and rocks as a function of local conditions and (v) relations between melting and melt transport dynamics in 3-D and crustal growth (volcanic activity) at the surface. By comparing with seismic structure and petrological observations in the southern Alaskan subduction zone, we will get a robust oceanic-continental subduction model with well- constrained controlling parameters particularly applicable for this zone.We request funding for two years for one postdoc and research costs involved with her work. This project builds on a previous SNF-funded postdoc project. This continuing support of a promising female scientist will help SNF to achieve the goal stated on its web site "to counter the under-representation of women scientists among the beneficiaries of the funding programmes".
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