Abstract
The South American subduction zone is enigmatic due to its fast subducting plate consumption, strong oscillation in subducting plate velocity, and deep mantle subduction. A key to help understand these subduction zone characteristics is through studying its dynamics with buoyancy-driven numerical modeling that uses independent variables to best approximate the dynamics of the real subduction system. We conduct a parametric investigation on the effect of upper mantle rheology, subduction interface yield stress and slab thermal weakening. To constrain those model variables, we attempt to find best-fits by comparing our model outcomes with the present-day slab geometry and estimates of Cenozoic velocities in the center of the South American subduction zone. Key ingredients that need to be reproduced are low slab dip angles close to the surface, steeper lower mantle dip angles, strong oscillation of the fast Farallon-Nazca subducting plate velocity and a progressive decrease in trench retreat rate during long-term subduction. We include these ingredients to define a model fitting score using 10 criteria. Our best fitting models involve a weak subduction zone interface (yield stress of ∼20 MPa) and significant slab thermal weakening to attain the fast Farallon-Nazca subducting plate velocity and to better reproduce the subduction partitioning since 48 Ma due to reduced shear stresses resisting downdip slab sinking and reduced slab bending resistance. Furthermore, a non-Newtonian upper mantle promotes slab folding and realistic oscillation of the subducting plate velocity. Whether and how this slab folding process induces temporal variations in Andean deformation remains an open question.
Original language | English |
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Article number | e2020JB021527 |
Pages (from-to) | 1-33 |
Number of pages | 33 |
Journal | Journal of Geophysical Research: Solid Earth |
Volume | 126 |
Issue number | 4 |
Early online date | 15 Mar 2021 |
DOIs | |
Publication status | Published - Apr 2021 |
Bibliographical note
Funding Information:We would like to thank Arijit Laik, João Duarte, Filipe Rosas, Anouk Beniest, and Kai Xue for discussions on subduction dynamics and numerical subduction modeling. We acknowledge Julian Giordani, John Mansour and Arijit Laik for their technical assistance with the code. We also thank Fabio Crameri and Adam Beall for their thoughtful reviews that have improved the manuscript. This work has been funded by a Vici Fellowship (016.VICI.170.110) from the Dutch National Science Foundation (NWO) awarded to WPS. Furthermore, this work has been sponsored by NWO Exact and Natural Sciences for the use of supercomputer facilities. The work has also been supported by computational resources from the NCI National Facility in Australia through the National Computational Merit Allocation Scheme (project qk0). Several figures were made using the free software package GMT (Wessel et al., 2013 ) and use colors taken from the Scientific color maps and Center for Exploration Targeting websites (Crameri, 2020 ; Crameri et al., 2020 ; Kovesi, 2020 ). Underworld2
Funding Information:
We would like to thank Arijit Laik, Jo?o Duarte, Filipe Rosas, Anouk Beniest, and Kai Xue for discussions on subduction dynamics and numerical subduction modeling. We acknowledge Julian Giordani, John Mansour and Arijit Laik for their technical assistance with the Underworld2 code. We also thank Fabio Crameri and Adam Beall for their thoughtful reviews that have improved the manuscript. This work has been funded by a Vici Fellowship (016.VICI.170.110) from the Dutch National Science Foundation (NWO) awarded to WPS. Furthermore, this work has been sponsored by NWO Exact and Natural Sciences for the use of supercomputer facilities. The work has also been supported by computational resources from the NCI National Facility in Australia through the National Computational Merit Allocation Scheme (project qk0). Several figures were made using the free software package GMT (Wessel et?al.,?2013) and use colors taken from the Scientific color maps and Center for Exploration Targeting websites (Crameri,?2020; Crameri et?al.,?2020; Kovesi,?2020).
Publisher Copyright:
© 2021. The Authors.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
Keywords
- geodynamics
- numerical modeling
- South America
- subduction