Crustal shortening, exhumation, and strain localization in a collisional orogen: The Bajo Pequeño Shear Zone, Sierra de Pie de Palo, Argentina
The Bajo Pequeño Shear Zone (BPSZ) is a lower-crustal shear zone that records shortening and exhumation associated with the establishment of a new plate boundary, and its placement in a regional structural context suggests that local- to regional-scale strain localization occurred with progressive d...
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paper:paper_02787407_v33_n7_p1277_Garber2023-06-08T15:26:53Z Crustal shortening, exhumation, and strain localization in a collisional orogen: The Bajo Pequeño Shear Zone, Sierra de Pie de Palo, Argentina Vujovich, Graciela Irene collisional orogen convergent margin ductile shear zone lower crust Pie de Palo Mica Quartz Tectonics Collisional Convergent margin Ductile shear zone Lower crust Pie de Palo Deformation argon-argon dating collision zone continental crust convergent margin crustal shortening ductile deformation exhumation Gondwana lower crust microplate orthogneiss shear strain shear zone tectonics Argentina Precordillera San Juan [Argentina] Sierra de Pie de Palo Sierras Pampeanas The Bajo Pequeño Shear Zone (BPSZ) is a lower-crustal shear zone that records shortening and exhumation associated with the establishment of a new plate boundary, and its placement in a regional structural context suggests that local- to regional-scale strain localization occurred with progressive deformation. A kilometer-scale field and analytical cross section through the ~80 m thick BPSZ and its adjacent rocks indicates an early Devonian (405-400Ma) phase of deformation on the western margin of Gondwanan continental crust. The earliest stages of the BPSZ, recorded by metamorphic and microstructural data, involved thrusting of a hotter orthogneiss over a relatively cool pelitic unit, which resulted in footwall garnet growth and reset footwall white mica 40Ar/39Ar ages in proximity to the shear zone. Later stages of BPSZ activity, as recorded by additional microstructures and quartz c-axis opening angles, were characterized by strain localization to the center of the shear zone coincident with cooling and exhumation. These and other data suggest that significant regional tectonism persisted in the Famatinian orogenic system for 60-70 million years after one microplate collision (the Precordillera) but ceased 5-10 million years prior to another (Chilenia). A survey of other synchronous structures shows that strain was accommodated on progressively narrower structures with time, indicating a regional pattern of strain localization and broad thermal relaxation as the Precordillera collision evolved. Key Points BPSZ deformation is associated with the establishment of a new plate boundary Strain localization in the BPSZ overprints an early inverted thermal gradient Structures in the Famatinian system show strain localization over ∼70 Myr © 2014. American Geophysical Union. All Rights Reserved. Fil:Vujovich, G.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2014 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_02787407_v33_n7_p1277_Garber http://hdl.handle.net/20.500.12110/paper_02787407_v33_n7_p1277_Garber |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
collisional orogen convergent margin ductile shear zone lower crust Pie de Palo Mica Quartz Tectonics Collisional Convergent margin Ductile shear zone Lower crust Pie de Palo Deformation argon-argon dating collision zone continental crust convergent margin crustal shortening ductile deformation exhumation Gondwana lower crust microplate orthogneiss shear strain shear zone tectonics Argentina Precordillera San Juan [Argentina] Sierra de Pie de Palo Sierras Pampeanas |
| spellingShingle |
collisional orogen convergent margin ductile shear zone lower crust Pie de Palo Mica Quartz Tectonics Collisional Convergent margin Ductile shear zone Lower crust Pie de Palo Deformation argon-argon dating collision zone continental crust convergent margin crustal shortening ductile deformation exhumation Gondwana lower crust microplate orthogneiss shear strain shear zone tectonics Argentina Precordillera San Juan [Argentina] Sierra de Pie de Palo Sierras Pampeanas Vujovich, Graciela Irene Crustal shortening, exhumation, and strain localization in a collisional orogen: The Bajo Pequeño Shear Zone, Sierra de Pie de Palo, Argentina |
| topic_facet |
collisional orogen convergent margin ductile shear zone lower crust Pie de Palo Mica Quartz Tectonics Collisional Convergent margin Ductile shear zone Lower crust Pie de Palo Deformation argon-argon dating collision zone continental crust convergent margin crustal shortening ductile deformation exhumation Gondwana lower crust microplate orthogneiss shear strain shear zone tectonics Argentina Precordillera San Juan [Argentina] Sierra de Pie de Palo Sierras Pampeanas |
| description |
The Bajo Pequeño Shear Zone (BPSZ) is a lower-crustal shear zone that records shortening and exhumation associated with the establishment of a new plate boundary, and its placement in a regional structural context suggests that local- to regional-scale strain localization occurred with progressive deformation. A kilometer-scale field and analytical cross section through the ~80 m thick BPSZ and its adjacent rocks indicates an early Devonian (405-400Ma) phase of deformation on the western margin of Gondwanan continental crust. The earliest stages of the BPSZ, recorded by metamorphic and microstructural data, involved thrusting of a hotter orthogneiss over a relatively cool pelitic unit, which resulted in footwall garnet growth and reset footwall white mica 40Ar/39Ar ages in proximity to the shear zone. Later stages of BPSZ activity, as recorded by additional microstructures and quartz c-axis opening angles, were characterized by strain localization to the center of the shear zone coincident with cooling and exhumation. These and other data suggest that significant regional tectonism persisted in the Famatinian orogenic system for 60-70 million years after one microplate collision (the Precordillera) but ceased 5-10 million years prior to another (Chilenia). A survey of other synchronous structures shows that strain was accommodated on progressively narrower structures with time, indicating a regional pattern of strain localization and broad thermal relaxation as the Precordillera collision evolved. Key Points BPSZ deformation is associated with the establishment of a new plate boundary Strain localization in the BPSZ overprints an early inverted thermal gradient Structures in the Famatinian system show strain localization over ∼70 Myr © 2014. American Geophysical Union. All Rights Reserved. |
| author |
Vujovich, Graciela Irene |
| author_facet |
Vujovich, Graciela Irene |
| author_sort |
Vujovich, Graciela Irene |
| title |
Crustal shortening, exhumation, and strain localization in a collisional orogen: The Bajo Pequeño Shear Zone, Sierra de Pie de Palo, Argentina |
| title_short |
Crustal shortening, exhumation, and strain localization in a collisional orogen: The Bajo Pequeño Shear Zone, Sierra de Pie de Palo, Argentina |
| title_full |
Crustal shortening, exhumation, and strain localization in a collisional orogen: The Bajo Pequeño Shear Zone, Sierra de Pie de Palo, Argentina |
| title_fullStr |
Crustal shortening, exhumation, and strain localization in a collisional orogen: The Bajo Pequeño Shear Zone, Sierra de Pie de Palo, Argentina |
| title_full_unstemmed |
Crustal shortening, exhumation, and strain localization in a collisional orogen: The Bajo Pequeño Shear Zone, Sierra de Pie de Palo, Argentina |
| title_sort |
crustal shortening, exhumation, and strain localization in a collisional orogen: the bajo pequeño shear zone, sierra de pie de palo, argentina |
| publishDate |
2014 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_02787407_v33_n7_p1277_Garber http://hdl.handle.net/20.500.12110/paper_02787407_v33_n7_p1277_Garber |
| work_keys_str_mv |
AT vujovichgracielairene crustalshorteningexhumationandstrainlocalizationinacollisionalorogenthebajopequenoshearzonesierradepiedepaloargentina |
| _version_ |
1768542267730034688 |