Electrical conductivity of the Pampean shallow subduction region of Argentina near 33 S: Evidence for a slab window
We present a three-dimensional (3-D) interpretation of 117 long period (20-4096 s) magnetotelluric (MT) sites between 31°S and 35°S in western Argentina. They cover the most horizontal part of the Pampean shallow angle subduction of the Nazca Plate and extend south into the more steeply dipping regi...
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2013
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paper:paper_15252027_v14_n8_p3192_Burd2023-06-08T16:19:30Z Electrical conductivity of the Pampean shallow subduction region of Argentina near 33 S: Evidence for a slab window Nazca flat slab subduction slab window three-dimensional magnetotelluric inversion Magnetotellurics Three dimensional Electrical conductivity Electrically conductive Flat-slab subductions Mantle transition zone Non linear conjugate gradient (NLCG) Slab windows Threedimensional (3-d) Wadati-Benioff Zones Tectonics Benioff zone electrical conductivity lithospheric structure magnetotelluric method mantle structure Nazca plate seismicity slab subduction transition zone Argentina Sierras Pampeanas We present a three-dimensional (3-D) interpretation of 117 long period (20-4096 s) magnetotelluric (MT) sites between 31°S and 35°S in western Argentina. They cover the most horizontal part of the Pampean shallow angle subduction of the Nazca Plate and extend south into the more steeply dipping region. Sixty-two 3-D inversions using various smoothing parameters and data misfit goals were done with a nonlinear conjugate gradient (NLCG) algorithm. A dominant feature of the mantle structure east of the horizontal slab is a conductive plume rising from near the top of the mantle transition zone at 410 km to the probable base of the lithosphere at 100 km depth. The subducted slab is known to descend to 190 km just west of the plume, but the Wadati-Benioff zone cannot be traced deeper. If the slab is extrapolated downdip it slices through the plume at 250 km depth. Removal of portions of the plume or blocking vertical current flow at 250 km depth significantly changes the predicted responses. This argues that the plume is not an artifact and that it is continuous. The simplest explanation is that there is a "wedge"-shaped slab window that has torn laterally and opens down to the east with its apex at the plume location. Stress within the slab and seismic tomography support this shape. Its northern edge likely explains why there is no deep seismicity south of 29°S. Key Points Electrically conductive plume in Argentina's asthenosphere suggests slab window Three-dimensional magnetotelluric inversion is required for data presented ©2013. American Geophysical Union. All Rights Reserved. 2013 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15252027_v14_n8_p3192_Burd http://hdl.handle.net/20.500.12110/paper_15252027_v14_n8_p3192_Burd |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Nazca flat slab subduction slab window three-dimensional magnetotelluric inversion Magnetotellurics Three dimensional Electrical conductivity Electrically conductive Flat-slab subductions Mantle transition zone Non linear conjugate gradient (NLCG) Slab windows Threedimensional (3-d) Wadati-Benioff Zones Tectonics Benioff zone electrical conductivity lithospheric structure magnetotelluric method mantle structure Nazca plate seismicity slab subduction transition zone Argentina Sierras Pampeanas |
| spellingShingle |
Nazca flat slab subduction slab window three-dimensional magnetotelluric inversion Magnetotellurics Three dimensional Electrical conductivity Electrically conductive Flat-slab subductions Mantle transition zone Non linear conjugate gradient (NLCG) Slab windows Threedimensional (3-d) Wadati-Benioff Zones Tectonics Benioff zone electrical conductivity lithospheric structure magnetotelluric method mantle structure Nazca plate seismicity slab subduction transition zone Argentina Sierras Pampeanas Electrical conductivity of the Pampean shallow subduction region of Argentina near 33 S: Evidence for a slab window |
| topic_facet |
Nazca flat slab subduction slab window three-dimensional magnetotelluric inversion Magnetotellurics Three dimensional Electrical conductivity Electrically conductive Flat-slab subductions Mantle transition zone Non linear conjugate gradient (NLCG) Slab windows Threedimensional (3-d) Wadati-Benioff Zones Tectonics Benioff zone electrical conductivity lithospheric structure magnetotelluric method mantle structure Nazca plate seismicity slab subduction transition zone Argentina Sierras Pampeanas |
| description |
We present a three-dimensional (3-D) interpretation of 117 long period (20-4096 s) magnetotelluric (MT) sites between 31°S and 35°S in western Argentina. They cover the most horizontal part of the Pampean shallow angle subduction of the Nazca Plate and extend south into the more steeply dipping region. Sixty-two 3-D inversions using various smoothing parameters and data misfit goals were done with a nonlinear conjugate gradient (NLCG) algorithm. A dominant feature of the mantle structure east of the horizontal slab is a conductive plume rising from near the top of the mantle transition zone at 410 km to the probable base of the lithosphere at 100 km depth. The subducted slab is known to descend to 190 km just west of the plume, but the Wadati-Benioff zone cannot be traced deeper. If the slab is extrapolated downdip it slices through the plume at 250 km depth. Removal of portions of the plume or blocking vertical current flow at 250 km depth significantly changes the predicted responses. This argues that the plume is not an artifact and that it is continuous. The simplest explanation is that there is a "wedge"-shaped slab window that has torn laterally and opens down to the east with its apex at the plume location. Stress within the slab and seismic tomography support this shape. Its northern edge likely explains why there is no deep seismicity south of 29°S. Key Points Electrically conductive plume in Argentina's asthenosphere suggests slab window Three-dimensional magnetotelluric inversion is required for data presented ©2013. American Geophysical Union. All Rights Reserved. |
| title |
Electrical conductivity of the Pampean shallow subduction region of Argentina near 33 S: Evidence for a slab window |
| title_short |
Electrical conductivity of the Pampean shallow subduction region of Argentina near 33 S: Evidence for a slab window |
| title_full |
Electrical conductivity of the Pampean shallow subduction region of Argentina near 33 S: Evidence for a slab window |
| title_fullStr |
Electrical conductivity of the Pampean shallow subduction region of Argentina near 33 S: Evidence for a slab window |
| title_full_unstemmed |
Electrical conductivity of the Pampean shallow subduction region of Argentina near 33 S: Evidence for a slab window |
| title_sort |
electrical conductivity of the pampean shallow subduction region of argentina near 33 s: evidence for a slab window |
| publishDate |
2013 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15252027_v14_n8_p3192_Burd http://hdl.handle.net/20.500.12110/paper_15252027_v14_n8_p3192_Burd |
| _version_ |
1768546084571840512 |