Constraining a mafic thick crust model in the Andean Precordillera of the Pampean flat slab subduction region
Elastic properties in twelve representative rock samples from Central and Western Precordillera in the Andean backarc region of Argentina between 30 and 31°S were estimated from detailed petrological analysis. Thus, P and S seismic-wave velocities (Vp, Vs) as well as Poisson's ratio (σ) among o...
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08959811_v64_n_p325_PerezLujan http://hdl.handle.net/20.500.12110/paper_08959811_v64_n_p325_PerezLujan |
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paper:paper_08959811_v64_n_p325_PerezLujan2023-06-08T15:48:49Z Constraining a mafic thick crust model in the Andean Precordillera of the Pampean flat slab subduction region Vujovich, Graciela Irene Continental crust Flat slab subduction Mafic-ultramafic lithology Seismic velocities Western Andean Precordillera crustal thickness elastic property lithology mafic rock modeling Moho Nazca plate P-wave petrology rock property S-wave seismic velocity slab subduction suture zone terrane ultramafic rock wave velocity Argentina Precordillera Elastic properties in twelve representative rock samples from Central and Western Precordillera in the Andean backarc region of Argentina between 30 and 31°S were estimated from detailed petrological analysis. Thus, P and S seismic-wave velocities (Vp, Vs) as well as Poisson's ratio (σ) among other parameters were derived for gabbros, leuco-gabbros and wehrlites, in greenschist and amphibolite metamorphic conditions using a framework of a wide variety of empirical observations from active continental margins. In addition, Vs lithosphere models along two west-east cross sections were obtained using a joint inversion of teleseismic Rayleigh waves and receiver functions. These models clearly delineate the upper-plate crustal structure and the flat-slab subduction of the Nazca plate at about 100 km depth in this region. The suggested seismic velocity structure shows a relatively low (<3.3 km/s) Vs layer located in the first 15-18 km depth, then an increase of it from 3.3 to 4 km/s between 20 and 55 km depth with a mayor change at 40 km depth beneath the Precordillera showing an increase in Vs from 3.3 to 3.8 km/s. The Moho discontinuity was identified at around 65 km depth beneath the Precordillera (Vs = 4.3 km/s) and shows a low shear-wave velocity contrast in comparison with the upper continental mantle's parameters. Using this seismological model, Vs estimations derived from the petrological analyses for the 12 collected samples can be projected at depths greater than 30 km. These geophysical and petrological results agree with the hypothesis of a mafic thickened and partially eclogitized lower crust beneath the Precordillera, which has been predicted previously on a base of seismological studies only. Our petrological and seismological results collectively support a thick crustal model of a mafic-ultramafic composition extending to middle-to-lower crustal levels beneath Central and Western Precordillera; this region correlates with a suture zone between the eastern Cuyania terrane and the western Chilenia terrane. © 2015 Elsevier Ltd. Fil:Vujovich, G.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2015 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08959811_v64_n_p325_PerezLujan http://hdl.handle.net/20.500.12110/paper_08959811_v64_n_p325_PerezLujan |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Continental crust Flat slab subduction Mafic-ultramafic lithology Seismic velocities Western Andean Precordillera crustal thickness elastic property lithology mafic rock modeling Moho Nazca plate P-wave petrology rock property S-wave seismic velocity slab subduction suture zone terrane ultramafic rock wave velocity Argentina Precordillera |
| spellingShingle |
Continental crust Flat slab subduction Mafic-ultramafic lithology Seismic velocities Western Andean Precordillera crustal thickness elastic property lithology mafic rock modeling Moho Nazca plate P-wave petrology rock property S-wave seismic velocity slab subduction suture zone terrane ultramafic rock wave velocity Argentina Precordillera Vujovich, Graciela Irene Constraining a mafic thick crust model in the Andean Precordillera of the Pampean flat slab subduction region |
| topic_facet |
Continental crust Flat slab subduction Mafic-ultramafic lithology Seismic velocities Western Andean Precordillera crustal thickness elastic property lithology mafic rock modeling Moho Nazca plate P-wave petrology rock property S-wave seismic velocity slab subduction suture zone terrane ultramafic rock wave velocity Argentina Precordillera |
| description |
Elastic properties in twelve representative rock samples from Central and Western Precordillera in the Andean backarc region of Argentina between 30 and 31°S were estimated from detailed petrological analysis. Thus, P and S seismic-wave velocities (Vp, Vs) as well as Poisson's ratio (σ) among other parameters were derived for gabbros, leuco-gabbros and wehrlites, in greenschist and amphibolite metamorphic conditions using a framework of a wide variety of empirical observations from active continental margins. In addition, Vs lithosphere models along two west-east cross sections were obtained using a joint inversion of teleseismic Rayleigh waves and receiver functions. These models clearly delineate the upper-plate crustal structure and the flat-slab subduction of the Nazca plate at about 100 km depth in this region. The suggested seismic velocity structure shows a relatively low (<3.3 km/s) Vs layer located in the first 15-18 km depth, then an increase of it from 3.3 to 4 km/s between 20 and 55 km depth with a mayor change at 40 km depth beneath the Precordillera showing an increase in Vs from 3.3 to 3.8 km/s. The Moho discontinuity was identified at around 65 km depth beneath the Precordillera (Vs = 4.3 km/s) and shows a low shear-wave velocity contrast in comparison with the upper continental mantle's parameters. Using this seismological model, Vs estimations derived from the petrological analyses for the 12 collected samples can be projected at depths greater than 30 km. These geophysical and petrological results agree with the hypothesis of a mafic thickened and partially eclogitized lower crust beneath the Precordillera, which has been predicted previously on a base of seismological studies only. Our petrological and seismological results collectively support a thick crustal model of a mafic-ultramafic composition extending to middle-to-lower crustal levels beneath Central and Western Precordillera; this region correlates with a suture zone between the eastern Cuyania terrane and the western Chilenia terrane. © 2015 Elsevier Ltd. |
| author |
Vujovich, Graciela Irene |
| author_facet |
Vujovich, Graciela Irene |
| author_sort |
Vujovich, Graciela Irene |
| title |
Constraining a mafic thick crust model in the Andean Precordillera of the Pampean flat slab subduction region |
| title_short |
Constraining a mafic thick crust model in the Andean Precordillera of the Pampean flat slab subduction region |
| title_full |
Constraining a mafic thick crust model in the Andean Precordillera of the Pampean flat slab subduction region |
| title_fullStr |
Constraining a mafic thick crust model in the Andean Precordillera of the Pampean flat slab subduction region |
| title_full_unstemmed |
Constraining a mafic thick crust model in the Andean Precordillera of the Pampean flat slab subduction region |
| title_sort |
constraining a mafic thick crust model in the andean precordillera of the pampean flat slab subduction region |
| publishDate |
2015 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08959811_v64_n_p325_PerezLujan http://hdl.handle.net/20.500.12110/paper_08959811_v64_n_p325_PerezLujan |
| work_keys_str_mv |
AT vujovichgracielairene constrainingamaficthickcrustmodelintheandeanprecordilleraofthepampeanflatslabsubductionregion |
| _version_ |
1768545934021492736 |