Analysis of strained microfabrics in the "Porfidos Rioliticos". Basement area of Pigüe, Sierras Australes de Buenos Aires

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knowledge of the initial shape of strain markers allows calculation of the strain ellipsoid (axial relationships and orientation) when they show distorted geometries after deformation. This information is usually combined with the analysis of other micro- and mesostructures that constitute the dynam...

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Autores principales: Japas, M.S., Sellés-Martinez, J.
Formato: JOUR
Materias:
basement rock
deformation
rock microstructure
strain analysis
Argentina
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00044822_v53_n3_p317_Japas
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_00044822_v53_n3_p317_Japas2023-10-03T13:57:26Z Analysis of strained microfabrics in the "Porfidos Rioliticos". Basement area of Pigüe, Sierras Australes de Buenos Aires Japas, M.S. Sellés-Martinez, J. basement rock deformation rock microstructure strain analysis Argentina knowledge of the initial shape of strain markers allows calculation of the strain ellipsoid (axial relationships and orientation) when they show distorted geometries after deformation. This information is usually combined with the analysis of other micro- and mesostructures that constitute the dynamic framework in which the whole assemblage of structures developed. If only one deformational episode was responsible for all of them, the result is a highly coherent picture. In this paper, the quantification of strain and orientation of strain axes, is attempted on the basis of distorted hexagonal columns cropping out close to Puesto El Malabar (Pigüé, Sierras Australes de Buenos Aires). This columnar strucutre occurs in rhyolitic flows and tuffs of the Precambrian (?) basement in the area. It is apparent from this study that deformation in the central part of the north-western arc of Sierras Australes is markedly heterogeneous at all scales, with axial relationships giving values that record a variationin between almost no deformation and belts of high strain in which cleavage erases all evidence of columnar jointing. Micro- and mesostructural analysis shows dextral simple shear in plan view, oriented Az.145°-150° , and E-W stripes of sinistral shear that appear to be later and fewer than the earlier, one. Evidence of shear to the NE in vertical section has been found that is also heterogeneously developed. Secondary microstructures also show geometric relationships that are coherent with the general picture in the area. The regional significance of these data is analyzed in the regional picture, and it is concluded that it fits the previous model of an arcuate belt resulting from local development of conjugate megashears, with E-W (sinistral) and SW-NE (dextral) bands shaping the arc. © 1998 Asociación Geológica Argentina. Fil:Japas, M.S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Sellés-Martinez, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00044822_v53_n3_p317_Japas
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic basement rock
deformation
rock microstructure
strain analysis
Argentina
spellingShingle basement rock
deformation
rock microstructure
strain analysis
Argentina
Japas, M.S.
Sellés-Martinez, J.
Analysis of strained microfabrics in the "Porfidos Rioliticos". Basement area of Pigüe, Sierras Australes de Buenos Aires
topic_facet basement rock
deformation
rock microstructure
strain analysis
Argentina
description knowledge of the initial shape of strain markers allows calculation of the strain ellipsoid (axial relationships and orientation) when they show distorted geometries after deformation. This information is usually combined with the analysis of other micro- and mesostructures that constitute the dynamic framework in which the whole assemblage of structures developed. If only one deformational episode was responsible for all of them, the result is a highly coherent picture. In this paper, the quantification of strain and orientation of strain axes, is attempted on the basis of distorted hexagonal columns cropping out close to Puesto El Malabar (Pigüé, Sierras Australes de Buenos Aires). This columnar strucutre occurs in rhyolitic flows and tuffs of the Precambrian (?) basement in the area. It is apparent from this study that deformation in the central part of the north-western arc of Sierras Australes is markedly heterogeneous at all scales, with axial relationships giving values that record a variationin between almost no deformation and belts of high strain in which cleavage erases all evidence of columnar jointing. Micro- and mesostructural analysis shows dextral simple shear in plan view, oriented Az.145°-150° , and E-W stripes of sinistral shear that appear to be later and fewer than the earlier, one. Evidence of shear to the NE in vertical section has been found that is also heterogeneously developed. Secondary microstructures also show geometric relationships that are coherent with the general picture in the area. The regional significance of these data is analyzed in the regional picture, and it is concluded that it fits the previous model of an arcuate belt resulting from local development of conjugate megashears, with E-W (sinistral) and SW-NE (dextral) bands shaping the arc. © 1998 Asociación Geológica Argentina.
format JOUR
author Japas, M.S.
Sellés-Martinez, J.
author_facet Japas, M.S.
Sellés-Martinez, J.
author_sort Japas, M.S.
title Analysis of strained microfabrics in the "Porfidos Rioliticos". Basement area of Pigüe, Sierras Australes de Buenos Aires
title_short Analysis of strained microfabrics in the "Porfidos Rioliticos". Basement area of Pigüe, Sierras Australes de Buenos Aires
title_full Analysis of strained microfabrics in the "Porfidos Rioliticos". Basement area of Pigüe, Sierras Australes de Buenos Aires
title_fullStr Analysis of strained microfabrics in the "Porfidos Rioliticos". Basement area of Pigüe, Sierras Australes de Buenos Aires
title_full_unstemmed Analysis of strained microfabrics in the "Porfidos Rioliticos". Basement area of Pigüe, Sierras Australes de Buenos Aires
title_sort analysis of strained microfabrics in the "porfidos rioliticos". basement area of pigüe, sierras australes de buenos aires
url http://hdl.handle.net/20.500.12110/paper_00044822_v53_n3_p317_Japas
work_keys_str_mv AT japasms analysisofstrainedmicrofabricsintheporfidosrioliticosbasementareaofpiguesierrasaustralesdebuenosaires
AT sellesmartinezj analysisofstrainedmicrofabricsintheporfidosrioliticosbasementareaofpiguesierrasaustralesdebuenosaires
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