Postorogenic volcanism in the northern boundary of the eastern Sierras Pampeanas: Chronological constraints and their tectonic implications

This paper presents new geochronological data on the northern sector of the eastern Sierras Pampeanas, in the province of Santiago del Estero. The regional geology of this area is mainly composed by a series of granitoids of Late Proterozoic - Early Cambrian age that are intruded by supracrustal vol...

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Detalles Bibliográficos
Publicado: 2003
Materias:
Ambargasta
Brasiliano cycle
Pampean orogeny
Sierras Pampeanas
Volcanic rocks
Cambrian
crustal evolution
orogenic belt
Proterozoic
volcanism
Argentina
South America
Western Hemisphere
World
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00044822_v58_n4_p593_Leal
http://hdl.handle.net/20.500.12110/paper_00044822_v58_n4_p593_Leal
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paper:paper_00044822_v58_n4_p593_Leal2023-06-08T14:25:42Z Postorogenic volcanism in the northern boundary of the eastern Sierras Pampeanas: Chronological constraints and their tectonic implications Ambargasta Brasiliano cycle Pampean orogeny Sierras Pampeanas Volcanic rocks Cambrian crustal evolution orogenic belt Proterozoic volcanism Argentina Sierras Pampeanas South America Western Hemisphere World This paper presents new geochronological data on the northern sector of the eastern Sierras Pampeanas, in the province of Santiago del Estero. The regional geology of this area is mainly composed by a series of granitoids of Late Proterozoic - Early Cambrian age that are intruded by supracrustal volcanic rocks. A rhyodacitic body, unconformably emplaced in deformed granitoids, known as Los Burros Dacite is densely emplaced. by small rhyolitic dykes, known as the Oncan Rhyolite and are widely exposed in the Sierra de Ambargasta. These volcanic rocks were emplaced after important deformation and exhumation of the batholith, that occurred as a result of the Pampean orogeny. Geochronological data, obtained from zircons of Los Burros Dacite by SHRIMP II, allow to determine that this body has finished its cristallization around 512 ± 3.5Ma, with a superimposed hydrothermal event of 481 ± 1.5 Ma. This last hydrothermal effect is interpreted as associated with the emplacement of the Oncán Rhyolites. Based on previous structural data, geochemical and petrological analyses, and the new dates, it is possible to interpret the existence of a magmatic arc in the eastern Sierras Pampeanas developed during Late Precambrian to Early Cambrian times, as a result of east subduction of the Pampia terrane. The collision of this terrane controlled the main deformation and metamorphism of the region at about 530 Ma, exhumation of the batholith and the emplacement in Early Cambrian times of the acidic volcanic suites here described. On the other hand, the Sm-Nd model-ages compiled for central Argentina and adjacent areas, and the new analysis here presented, show two different basements: model-ages between 1,800 and 1,300 Ma are concentrated to the west of the Transbrasilian shear zone, while in the eastern sector model ages between 2,000 and 2,600 Ma are more common. The model age of 1,350 Ma for Los Burros Dacite, suggests a crust with more affinities with the western basement, than the Río de La Plata Craton. On these bases a tectonic hypothesis is presented to explain the geologic evolution of eastern Sierras Pampeanas in accordance with the existing data. © 2003 Asociación Geológica Argentina. 2003 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00044822_v58_n4_p593_Leal http://hdl.handle.net/20.500.12110/paper_00044822_v58_n4_p593_Leal
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Ambargasta
Brasiliano cycle
Pampean orogeny
Sierras Pampeanas
Volcanic rocks
Cambrian
crustal evolution
orogenic belt
Proterozoic
volcanism
Argentina
Sierras Pampeanas
South America
Western Hemisphere
World
spellingShingle Ambargasta
Brasiliano cycle
Pampean orogeny
Sierras Pampeanas
Volcanic rocks
Cambrian
crustal evolution
orogenic belt
Proterozoic
volcanism
Argentina
Sierras Pampeanas
South America
Western Hemisphere
World
Postorogenic volcanism in the northern boundary of the eastern Sierras Pampeanas: Chronological constraints and their tectonic implications
topic_facet Ambargasta
Brasiliano cycle
Pampean orogeny
Sierras Pampeanas
Volcanic rocks
Cambrian
crustal evolution
orogenic belt
Proterozoic
volcanism
Argentina
Sierras Pampeanas
South America
Western Hemisphere
World
description This paper presents new geochronological data on the northern sector of the eastern Sierras Pampeanas, in the province of Santiago del Estero. The regional geology of this area is mainly composed by a series of granitoids of Late Proterozoic - Early Cambrian age that are intruded by supracrustal volcanic rocks. A rhyodacitic body, unconformably emplaced in deformed granitoids, known as Los Burros Dacite is densely emplaced. by small rhyolitic dykes, known as the Oncan Rhyolite and are widely exposed in the Sierra de Ambargasta. These volcanic rocks were emplaced after important deformation and exhumation of the batholith, that occurred as a result of the Pampean orogeny. Geochronological data, obtained from zircons of Los Burros Dacite by SHRIMP II, allow to determine that this body has finished its cristallization around 512 ± 3.5Ma, with a superimposed hydrothermal event of 481 ± 1.5 Ma. This last hydrothermal effect is interpreted as associated with the emplacement of the Oncán Rhyolites. Based on previous structural data, geochemical and petrological analyses, and the new dates, it is possible to interpret the existence of a magmatic arc in the eastern Sierras Pampeanas developed during Late Precambrian to Early Cambrian times, as a result of east subduction of the Pampia terrane. The collision of this terrane controlled the main deformation and metamorphism of the region at about 530 Ma, exhumation of the batholith and the emplacement in Early Cambrian times of the acidic volcanic suites here described. On the other hand, the Sm-Nd model-ages compiled for central Argentina and adjacent areas, and the new analysis here presented, show two different basements: model-ages between 1,800 and 1,300 Ma are concentrated to the west of the Transbrasilian shear zone, while in the eastern sector model ages between 2,000 and 2,600 Ma are more common. The model age of 1,350 Ma for Los Burros Dacite, suggests a crust with more affinities with the western basement, than the Río de La Plata Craton. On these bases a tectonic hypothesis is presented to explain the geologic evolution of eastern Sierras Pampeanas in accordance with the existing data. © 2003 Asociación Geológica Argentina.
title Postorogenic volcanism in the northern boundary of the eastern Sierras Pampeanas: Chronological constraints and their tectonic implications
title_short Postorogenic volcanism in the northern boundary of the eastern Sierras Pampeanas: Chronological constraints and their tectonic implications
title_full Postorogenic volcanism in the northern boundary of the eastern Sierras Pampeanas: Chronological constraints and their tectonic implications
title_fullStr Postorogenic volcanism in the northern boundary of the eastern Sierras Pampeanas: Chronological constraints and their tectonic implications
title_full_unstemmed Postorogenic volcanism in the northern boundary of the eastern Sierras Pampeanas: Chronological constraints and their tectonic implications
title_sort postorogenic volcanism in the northern boundary of the eastern sierras pampeanas: chronological constraints and their tectonic implications
publishDate 2003
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00044822_v58_n4_p593_Leal
http://hdl.handle.net/20.500.12110/paper_00044822_v58_n4_p593_Leal
_version_ 1768545488516153344

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